Webcontrols.calendar Select Year

8/14/2019 Webcontrols.calendar Select Year

1/31

or the past 20 years, Johnsie Toys has been manufacturing and selling toys for

The companys top management officials are often on the road while trying to expand the

business to those parts of the world where the company does not yet have retail outlets. For

those officials to be able to efficiently manage the functioning of the company, they need to have

access to appropriate and updated information. To ensure that this is the case, four months ago

the company developed a Web site for internal use by the management. This Web site can be

accessed from any place in the world to obtain the required information.The Web site provides

several features that enable access to the following details:

Performance results of the company

Policies the company follows

Sales made by the retail outlets

Resource allocation and utilization

In addition, the Web site also provides a chat application that enables the officials to discuss

important matters online. All these features of the Web site help the officials to analyze the

current performance and plan for the future. Another significant use of this Web site is to provide

data for preparation of reports for presentations and seminars.

Since the introduction of this Web site four months ago, developers have constantly endeavored

to improve the site by providing more useful features.The latest suggestion,which topmanagement has just approved, is to have an application on the Web site that provides sales data

for different regions according to particular dates or years. This application, called SalesData,

will help in timely identification of sales trends so that management can make quick decisions and

formulate effective sales strategies. This application will also make it possible to assess daily or

yearly performance of the regions based on their sales, which will facilitate making decisions

about the commissions for the various regions. Moreover, by using this application, the officials

can monitor sales on a daily basis.

After analyzing the various available technologies, management decides to develop the

application using Visual Basic.NET and ADO.NET as the data access model because the .NET

Framework makes it easy to develop applications for the distributed Web environment and

supports cross-platform execution and interoperability. In addition, the .NET Framework makes


2/31

data available anytime, anywhere, and on any device.The choice of ADO.NET as the data access

model is quite obvious because it optimally utilizes the benefits of the .NET Framework. Currently,

it is the most efficient data access model for highly distributed Web applications.

Management chooses a five-member team, named the SalesDataTeam, to develop thisapplication. All the members of the SalesDataTeam are experienced programmers who have

developed applications using Visual Basic.NET and ADO.NET.

Before beginning to develop the application, the members of the SalesDataTeam determine the

development life cycle of the SalesData project. This life cycle is discussed in the following

section.

Project Life CycleEvery project has a development life cycle. Generally, the life cycle of a project consists of the

following three phases:

Project start

Project execution

Project end

Theproject startphase involves preparing the project plan and determining the desired result of

each phase. It also involves listing all the tasks that needs to be performed.This exhaustive list is

based on the research of the project team. After preparing this list, the team decides which tasks

are the most crucial. In addition, during this phase, the project manager assigns responsibilities to

the team members based on their expertise and experience.

The next phase of the project life cycle is the project execution phase. This phase involves the

actual development of the project. In this phase, the SalesDataTeam develops the SalesData

application. The project execution phase is divided into the following sequential stages:

Requirements analysis

High-level design

Low-level design

Construction

Testing


3/31

Acceptance

These stages will be discussed in detail in the next few sections.The last phase of the project life

cycle is the project end phase. During this phase, which takes place after the application is

deployed, the development team sorts out the problems.

Requirements Analysis

The requirements analysis stage involves analysis of the various requirements that the

application is expected to meet.This analysis identifies all the requirements to which the

application needs to cater.

In this stage, the SalesDataTeam asks the management officials what their requirements for the

SalesData application are. The team interviews the officials to find out all the elements they

consider before making a decision about the sales strategies. In addition, the SalesDataTeam

evaluates the applications that are currently on the company Web site to ascertain what features

those applications are not offering that might be beneficial. Then, the team analyzes its findings

and arrives at a consensus regarding the requirements for the SalesData application.

After gathering this information, the team decides that the SalesData application should enable auser to:

Select the desired region

Select a particular date or year

View the sales data after the user selects the region and date or year

High-Level DesignAfter the team identifies the requirements for the application, the next stage is to decide on the

formats for accepting the input and displaying the output of the application. During this high-level

design stage, the team documents all the specifications regarding the functioning of the

application, and then the project manager approves the design of the project.

During this stage, the SalesDataTeam designs a Web form that enables a user to select a

particular region from a list. Then, the user can choose a date (by selecting it from a calendar thatis displayed) or a year (by selecting it from a list).This form provides a button that, when clicked,

displays the sales data for the selected choices in a tabular format. If the required data does not

exist in the database, an appropriate message displays. Furthermore, the main form also provides

a button to reset all the controls.


4/31

Low-Level Design

The low-level design stage involves preparing a detailed design of the various modules to be used

for the application. In this stage, the SalesDataTeam makes decisions about how to establish a

connection with the relevant database and how to access the required data. The team alsodecides which classes and methods to use for developing the application. The data needed by the

SalesData application is available in a single table database.

Construction

The construction stage is the stage in which the development team builds the application. The

output of the low-level design stage is used as the input for this stage.In this stage, the

development team divides the responsibilities of the development work for the applicationdesigning the forms and writing the code among its members, and then the team carries out

the tasks.

Testing

The testing stage deals with the testing of the application after it is developed. In this stage, the

QA (quality assurance) team of the company (a team other than the development team) tests the

functionality of the application to ensure that it meets all the requirements specified in therequirements analysis stage. The QA team tests the application in various scenarios. It also tests

the application against the requirements specified in the requirements analysis stage and then

prepares a report of the test results. After the QA team gives this test report to the development

team, the development team rectifies the problems in the application.

Acceptance

In this stage, the company carries out testing of the projects developed for the clients.This testingis performed in accordance with the standards defined by the industry. The successful testing of

the project in this stage signifies the final acceptance of the project before release to the client. In

the case of the SalesData application, the QA team gives the final acceptance because this

application is being developed for the internal use of the company, not for any external client.

After the deployment of the application on the Web site, the SalesDataTeam provides support to

users if they face any problems while running the application.

Now, lets take a look at the structure of the database that the SalesData application will use.

The Database Structure


5/31

The database that the SalesData application will use to retrieve the desired sales data is a

Microsoft Access database called Sales. This database contains only one table: Sales. Figure 7-1

displays the design of the Sales table.

FIGURE 7-1 The design of the Sales table

The Sales table has Product Code as the primary key, and its data type is text. It also contains the

product name, units sold, price, date of sale, region, and total sales.

Summary

In this chapter, you learned that Johnsie Toys, a U.S. toy company interested in expanding

globally, uses an internal Web site for which a new application needs to be developed. Thecompany names the application SalesData and forms a five-member development team named

SalesDataTeam.

After this introduction, you learned about the different phases of the development life cycle of a

project and how the SalesDataTeam works through these phases. Finally, you learned about the

structure of the Sales database that the SalesData application will use. In the next chapter, you

will find out how to develop the SalesData application.

The Designing of Forms for the Application

As discussed in Chapter 7, the high-level design for the application involves designing two Web

forms. The main form of the SalesData application enables the user to specify the choices for

which the relevant sales data is displayed in the second form. Figure 8-1 displays the design of

the main form,and Figure 8-2 displays the design of the second form.

Before designing a Web form, you need to create it. The main form is created when you create a

new Web application project. (To learn more about creating a new Web application project and

creating and designing a Web form, refer to Appendix B, Introduction to Visual Basic.NET.) You


6/31

design a Web form by dragging the required controls from the Web Forms tab of the Toolbox and

then setting the properties for these controls. In the following sections, I talk about the various

controls on the two forms of the SalesData application and the properties assigned to them.

The Main FormName the main Web form ViewSalesData.aspx.As you can see in Figure 8-1, this form displays a

drop-down list containing all the regions. The form also allows users to specify whether they want

to view the sales data for a specific date or a specific year. This option is provided as a group of

radio buttons. The form also contains a calendar from which the user can select the desired date,

and another drop-down list enables the user to select the year. The form also contains two

buttons: View Sales and Reset. You use the View Sales button to display the relevant The three

labels on the form contain text for selecting the region, date, and year. You need to set threeproperties for each of these labels: ID, Text, and Visible. The ID property represents the object name

that you assign to the label to easily identify and refer to it in the code, and the Text property

represents the text that will appear for the label on the form.The value of the Visible property

indicates whether the label will be visible on the form. By default, the value of the Visible property

is set to True, which indicates that the label will be visible on the form. Table 8-1 describes the

properties for the three labels on the main form.

FIGURE 8-1 The design of the main form for the application


7/31

FIGURE 8-2 The design of the second form for the application

data in tabular format, and you use the Reset button to reset all the controls on the main form.

property list, select FlowLayout

Labels

The Visible property for the LblYear and LblDate labels is specified as False because these labels are not

visible on the main form when the application loads this form. These labels are visible only after

the user specifies whether he or she wants to view the sales data for a specific date or a specificyear. This involves setting validations,which Ill discuss in the How the Main Form Functions

section later in this chapter.

Drop-Down Lists

Below the LblRegion and LblYear labels on the form are drop-down lists for the regions and years,

respectively. The three properties set for these drop-down lists are ID, Items, and Visible. I mentioned

earlier in this chapter what the ID and Visible properties represent. The Items property represents thecollection of items that will appear in the drop-down list.


8/31

The ID property specified for the two drop-down lists is DDLRegion for the LblRegion label and DDLYear for

the LblYear label. The Visible property is set as True for the LblRegion label and as False for the LblYear

label. To specify the Items property, click on it in the Properties window, as shown in Figure 8-3.

FIGURE 8-3 The Itemsproperty selected in the Properties window

When you click on the Items property, an ellipsis button appears next to the (Collection) valuespecified for this property. Click on the ellipsis button to display the ListItem Collection Editor

dialog box, shown in Figure 8-4.

FIGURE 8-4 The ListItem Collection Editor dialog box


9/31

The ListItem Collection Editor dialog box contains two panes: Members and Properties. Because

no item has yet been specified for the drop-down list, both panes are empty. To add an item for

the list, click on the Add button. A ListItem appears in the Members pane and its properties

appear in the Properties pane, as shown in Figure 8-5.

In the ListItem Properties pane, you can specify whether you want the item to appear selected by

default in the drop-down list. The default functionality specifies that the first item you add for the

list appears selected in the drop-down list. If you want any other item to appear selected by

default, specify True for the Selected property of that item.In addition, you can specify the text that

you want for the added item and a value for the item. By default, the text that you specify

appears as the value of the item. Figure 8-6 displays the properties for the North item of the drop-

down list for the regions.

Now you can specify the properties for the other items in the drop-down list. Figure 8-7 displays

the items for the DDLRegion drop-down list.

FIGURE 8-5 The ListItem Collection Editor dialog box with an item added


10/31

FIGURE 8-6 The ListItem Collection Editor dialog box displaying the properties for the North item


11/31

FIGURE 8-7 The ListItem Collection Editor dialog box with items for the DDLRegion drop-down list


12/31

Figure 8-8 displays the items for the DDLYear drop-down list. For the item 2002, specify the Selected

property asTrue.

Below the LblDate label,add a calendar from which the user can select the desired date. Specify the

ID property for the calendar as CalSales and the Visible property as False.

Radio Buttons

A group of radio buttons on the form allows users to specify whether they want to view the sales

for a specific date or a specific year. Table 8-2 describes the properties you need to assign for

these radio buttons.

FIGURE 8-8 The ListItem Collection Editor dialog box with items for the DDLYear drop-down list


13/31


14/31

Note that the value for the GroupName property of both the radio buttons is set as GRP1. In this way,

you are specifying them as part of the same group, and the user is able to select only one radio

button from the group. The AutoPostBack property is set to True so that when the user selects a radio

button, the state of the radio buttons is automatically posted back to the server.

Buttons

The main form also contains two buttons.The properties that need to be assigned for these

buttons are described in Table 8-3.

When you add controls to the main form and specify their properties, the following code is

generated to indicate the declaration of all the objects that you drag to the Web form:

Protected WithEvents CalSales As System.Web.UI.WebControls.Calendar Protected WithEvents DDLYear As

System.Web.UI.WebControls.DropDownList Protected WithEvents DDLRegion As System.Web.UI.WebControls.DropDownList Protected

WithEvents BtnViewSales As System.Web.UI.WebControls.Button Protected WithEvents LblRegion As System.Web.UI.WebControls.Label

Protected WithEvents LblYear As System.Web.UI.WebControls.Label Protected WithEvents LblDate As System.Web.UI.WebControls.Label

Protected WithEvents RBDate As System.Web.UI.WebControls.RadioButton Protected WithEvents RBYear As

System.Web.UI.WebControls.RadioButton Protected WithEvents BtnReset As System.Web.UI.WebControls.Button

The Second FormNow that you know how to design the main form of the SalesData application, lets take a look at

the design of the second form. Name the second form SalesData.aspx. You can add the heading

Sales Data on the top of the form in the same way that you added the heading on the main form.

It also has the font size 7, is bold, and is center-aligned.

The label on the form has the ID property LBLUserMsg. This label is used to display information; the

text that is displayed depends on the choices the user makes in the main form. A data grid also

appears on the form; it displays the data retrieved from the database. To ensure that the font of

the column headings is bold, select Font under HeaderStyle, and then select True for the Bold property.

The form also contains a button with the ID property BtnOKand theText property OK.

The Functioning of the ApplicationNow that you understand the design of the two forms of the SalesData application, Ill discuss the

working of that application. First Ill explain how it works, and then Ill cover the code behind it.


15/31

How It Works

As you know, the SalesData application is a simple data access application that displays the sales

data of a region for a desired date or year. The main form (ViewSalesData.aspx) that appears

when the browser loads the application is displayed in Figure 8-9.

This form enables users to select the desired region from the drop-down list. To view the sales for

the selected region, users need to specify whether they want to view the sales for a specific date

or a specific year. To make this choice, they can simply select the relevant option. To view the

sales for a specific date, users needs to select the For a specific date option. In this case, the form

displays a calendar, as shown in Figure 8-10.This enables users to select the date for which they

want to view the sales data.

FIGURE 8-9 The main form in the browser

FIGURE 8-10 The main form with a calendar that enables users to select a date


16/31

After selecting the date from the calendar, users click on the View Sales button. This loads the

second form (SalesData.aspx), which displays the relevant data. Figure 8-11 displays the form

with the sales data of the North region on January 4, 2002.

FIGURE 8-11 The form displaying data for the selected region and date


17/31

If the database does not contain any records for the selection made by a user, an appropriate

message is displayed on the second form, as shown in Figure 8-12.

FIGURE 8-12 The form displaying a message when the relevant records are not present in the database


18/31

The second form displays an OK button, on which users can click to return to the main form. If

users want to view sales data for a specific year, they select the For a specific year option on the

main form. In this case, the form (as shown in Figure 8-13) displays a drop-down list from which

users can select the year for which they want to view the sales data.

After a user selects the year, the application works in the same way as it does when a user

selects a date. The main form of the application also provides a Reset button that,when clicked,

clears the selected choices to reset the controls to the original values.

The Code behind the Application

Now that you know how the SalesData application works, Ill discuss the code behind the

application that enables it to function.

How the Main Form Functions

As mentioned earlier in this chapter, when the main form of the application loads, some controls

(whose Visible property is set to False) are not visible to the user. These controls become visible or

remain hidden depending on the choices that the user makes.To enable this functionality,certain

validations are set.Take a look at the following code for the CheckedChanged event handler for the

selection in the radio button group. This code sets the Visible property of the various controls when


19/31

a user selects the For a specific date option. The code uses a simple If ... Then construct to execute

the logic.


20/31

Private Sub RBDate_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles

RBDate.CheckedChanged

Set the Visible property for the controls BtnViewSales.Visible = True BtnReset.Visible = True LblYear.Visible = False LblDate.Visible =

True RBDate.Visible = False CalSales.Visible = True RBYear.Visible = False DDLYear.Visible = False

End Sub

Similarly, the following code specifies that the controls will be visible when a user selects the For

a specific year option:

Private Sub RBYear_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RBYear.CheckedChanged

Set the Visible property for the controls BtnViewSales.Visible = True BtnReset.Visible = True LblYear.Visible = True LblDate.Visible =False RBYear.Visible = False CalSales.Visible = False RBDate.Visible = False DDLYear.Visible = True

End Sub

After a user selects the appropriate choices in the main form and clicks on the View Sales button,

the following code associated with the Click event of the BtnViewSales button executes:

Private Sub BtnViewSales_Click(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles BtnViewSales.Click Simple If loop to decide what SQL query to be executed according to the

selections made by the user

If CalSales.Visible = True And DDLYear.Visible = False Then

If DDLRegion.SelectedItem.Text = All Then SQL query to be stored in the SQLCommand property of the Standard module

Standard.SQLCommand = SELECT [Product Code], [Product Name], [Units Sold], [Price ($)], [Total Sales ($)] FROM Sales Where [Date

of Sale] = & CalSales.SelectedDate.Date.ToShortDateString &

Value to be stored in the ControlValue property of the

Standard module Standard.ControlValue = all the regions on & C a l S a l e s . S e l e c t e d D a t e . D a t e . T o S h o r t D a t e S t

r i n g

E l s e Standard.SQLCommand = SELECT [Product Code], [Product Name], [Units Sold], [Price ($)], [Total Sales ($)] FROM Sales Where

Region = & DDLRegion.SelectedItem.Text.Trim & and [Date of Sale] = & CalSales.SelectedDate & Standard.ControlValue =the & DDLRegion.SelectedItem.Text & region on & CalSales.SelectedDate.Date.ToShortDateString

End If ElseIf CalSales.Visible = False And DDLYear.Visible = True Then


21/31

If DDLRegion.SelectedItem.Text = All Then Standard.SQLCommand = SELECT [Product Code], [Product Name], [Units Sold], [Price

($)], [Total Sales ($)] FROM Sales Where Year([Date of Sale]) = & DDLYear.SelectedItem. Text & Standard.ControlValue = all the

regions in the year & D D L Y e a r . S e l e c t e d I t e m . T e x t


Region = & DDLRegion.SelectedItem.Text.Trim & and Year([Date of Sale]) = & DDLYear.SelectedItem. Text &

Standard.ControlValue = the &

DDLRegion.SelectedItem.Text & region in the year &

D D L Y e a r . S e l e c t e d I t e m . T e x t

End If

End If

Redirect to the SalesData page

R e s p o n s e . R e d i r e c t ( S a l e s D a t a . a s p x )

End Sub

In this code, the If ...Then construct contains code to determine the SQL query to be used according

to the selections made by the user. The SQL query that is generated retrieves records for the

Product Code, Product Name, Units Sold, Price ($), and Total Sales ($) columns of the Sales database. However,note that the Where condition of the query varies depending on the selections made by the user.

The Ifstatement in the code checks for the visibility of the calendar and the drop-down list for the

years. In case the Ifstatement evaluates to True, another If ... Then construct executes.

Note that this If ... Then construct uses the properties declared in the Standard module. The

Standard module is a Visual Basic.NET module with reusable code that is required across the

application. This module contains code for declaring two read-write properties. Before explainingthe SQL queries, Ill discuss the two properties declared in the Standard module. The following is

the code in the Standard module:

Module Standard

Declare two read-write property procedures

Declare a private variable to store the value assigned to the property

Private Command As String

Declare SQLCommand Property

Friend Property SQLCommand() As String


22/31

G e t

Return the value stored in the SQLCommand property

Return Command

End Get

Set(ByVal Value As String)

Set the property value and store it in the private variable,

Command

Command = Value End Set End Property

Private ControlSelectedValue As String Declare ControlValue Property Friend Property ControlValue() As String

G e t Return the value stored in the ControlValue property

Return ControlSelectedValue End Get Set(ByVal Value As String)

Set the property value and store it in the private variable, C o n t r o l S e l e c t e d V a l u e ControlSelectedValue = Value End Set

End Property End Module

The two properties declared in the Standard module are SQLCommand and ControlValue. In the previous

code, Command and ControlSelectedValue are private variables declared as strings and used for storing

the values assigned to the SQL-Command and ControlValue properties, respectively. Both the

SQLCommandand ControlValue properties are read-write properties for which the Set Property and Get

Property procedures are declared.The Set Property procedure sets the value of the property and stores

it in the private variable declared for it. The Get Property procedure returns the value stored in the

variable of the property.

Now, Ill discuss the following If ... Then construct (after the first Ifstatement evaluates to True) and

the SQL queries that are generated:



($)], [Total Sales ($)] FROM Sales Where [Date of Sale] = & CalSales.SelectedDate.Date.ToShortDateString & Standard.ControlValue = all the regions on & C a l S a l e s . S e l e c t e d D a t e . D a t e . T o S h o r t D a t e S t r i n g


23/31


Region = & DDLRegion.SelectedItem.Text.Trim & and [Date of Sale] = & CalSales.SelectedDate & Standard.ControlValue =

the & DDLRegion.SelectedItem. Text & region on & C a l S a l e s . S e l e c t e d D a t e . D a t e . T o S h o r t D a t e S t r i n g

End If

The Ifstatement checks whether All is selected in the drop-down list for the regions. In case the If

statement evaluates toTrue, the Where condition of the SQL query specifies that the value in the

Date of Salecolumn should match the date selected in the calendar. The SQL query is stored in the

SQLCommand property declared in the Standard module. In addition, the selected option values also

get stored in the ControlValue property of the Standard module. (These values are used for

LBLUserMsg, a label youll learn about later in this chapter.) However, in case the Ifstatement

evaluates to False, the SQL query retrieves records based on a different Where condition.

Furthermore, if a user wants to view the sales data for a specific year, the first Ifstatement (which

checks for the visibility of the calendar and the drop-down list for the years) evaluates to False. In

that case, the ElseIf ... Then construct following the first If ... Then construct executes to determine the

SQL query to be used:

ElseIf CalSales.Visible = False And DDLYear.Visible = True Then


($)], [Total Sales ($)] FROM Sales Where Year([Date of Sale]) = &

DDLYear.SelectedItem.Text & Standard.ControlValue = all the regions in the year & D D L Y e a r . S e l e c t e d I t e m . T e x t


Region = & DDLRegion.SelectedItem.Text.Trim & and Year([Date of Sale]) = & DDLYear.SelectedItem.Text &

Standard.ControlValue = the & DDLRegion.SelectedItem.Text & region in the year & DDLYear.SelectedItem.Text End If

When users click on the View Sales button, they are redirected to the SalesData.aspx page that

displays the data for the selected choices. The code for this redirection is also written in the Click

event of the View Sales button.

As mentioned earlier, you can use the Reset button to clear all the options the user selects. This is

possible because the Click event of the Reset button reloads the ViewSalesData.aspx page. The

code for this is as follows:

Private Sub BtnReset_Click(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles BtnReset.Click Reload the page R e s p o n s e . R e d i r e c t ( V i e w S a l e s D a t a . a s p x

)


24/31

End Sub

How the Second Form Functions

Now that you know how the main form of the application functions, Ill discuss the functioning of

the second form. When a user clicks on the View Sales button on the main form, the followingcode attached to the Load event of the second form executes:

Create an object of the type OleDbConnection Dim Conn As OleDbConnection Private Sub Page_Load(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles MyBase.Load

Try block is used for code whose exceptions are handled by the catch block T r y Declare an integer variable to validate the number

of rows returned

Dim RowCount As Integer Specify the connection string Conn = New OleDbConnection(Provider=Microsoft.Jet.OLEDB.4.0; & _ Data

source= & Request.PhysicalApplicationPath & /Sales.mdb;) Open the connection C o n n . O p e n ( ) Create an object of the

OleDbDataAdapter class and pass the SQL command and the connection information as parameters

Dim AdapObj As OleDbDataAdapter = New OleDbDataAdapter (Standard.SQLCommand, Conn) Create a dataset object Dim DstObj As

DataSet = New DataSet() Call the Fill method of the OleDbDataAdapter object to fil l the dataset AdapObj.Fill(DstObj, SalesTable)

Store the result as the number of rows returned RowCount = DstObj.Tables(SalesTable).Rows.Count Check the number of rows

stored in the RowCount variable If RowCount > 0 Then

If rows are greater than 0, then the data is displayed in the datagrid control Label to display information LBLUserMsg.Text = For &

Standard.ControlValue Specify the DataSource property of the control to the dataset object DataGrid1.DataSource = DstObj Bind the

data in the dataset to the control D a t a G r i d 1 . D a t a B i n d ( )

E l s e If no rows are returned, then the label is displayed with appropriate message LBLUserMsg.Text = No Records Available

End If Catch block is basically used to trap all the exceptions/error information that might occur in executing the code in the try

block.

Catch RunException As Exception Declare a variable of the type exception Write the error message for the user reference

Response.Write(Error Occured: & vbLf & RunException.ToString) The cleanup code comes here F i n a l l y Close the connection C o

n n . C l o s e ( ) End Try End Sub

In this code, the Try, Catch, and Finally blocks are used to write the code. The Try block is used for the

executable code. The Catch block is used for the code that handles the exception generated by the

code in the Try block. The Finally block is used to release the resources used.

As mentioned earlier in this chapter, for the second form (SalesData.aspx) to display the relevant

data retrieved from the database, the SalesData application makes use of ADO.NET. The database

that contains the relevant sales data, which the application needs to access, is a Microsoft Access

database. Therefore, the OLE DB .NET data provider is used to connect to the database, execute


25/31

commands, and retrieve results. Because the OLE DB .NET data provider is used, the

System.Data.OleDb namespace is imported so that you need not use the fully qualified names of the

classes and the objects:

Imports System.Data.OleDb

To establish a connection with the database, the OleDbConnection object is used and the connection

string property is declared.The following is the code to establish the connection:

Create an object of the type OleDbConnection Dim Conn As OleDbConnection Specify the connection string Conn = New

OleDbConnection(Provider=Microsoft.Jet.OLEDB.4.0; & _ Data source= & Request.PhysicalApplicationPath & /Sales.mdb;) Open

the connection C o n n . O p e n ( )

This code creates an object, Conn, of the OleDbConnection class. This object is used to specify theconnection string, which provides the name of the provider as Microsoft.Jet.OLEDB.4.0and the data

source as the Sales database that can be accessed from the physical application path. Next, the

object Conn calls the Open() method. This method establishes an open connection with the

database.As I discussed in Chapter 3, Connecting to a SQL Server and Other Data Sources,

there are various ways of writing a connection string, such as writing the connection string as a

string or using the connection object to declare a connection string. The previous code uses the

connection object to declare the connection string.

After a connection is established with the database, OleDbDataAdapter is used to communicate

between the database and the dataset. For this, an object of the OleDbDataAdapter class is created,

and the SQL command and the connection information are passed to it as parameters. The code

for this is as follows:

Create an object of the OleDbDataAdapter class and

pass the SQL command and the connection information as parameters Dim AdapObj As OleDbDataAdapter = New OleDbDataAdapter(Standard.SQLCommand, Conn)

In this code, AdapObj is the object of the OleDbDataAdapter class.The SQLCommand property stored in the

Standard module and the connection information specified for the Conn object are the parameters

for the AdapObj object. Instead of using the AdapObj object, you can use an OleDbCommand object.

OleDbCommand is used for processing requests and returning results of these requests. If you want

to use the OleDbCommand object, use the following code:

Create the object of type OleDbDataAdapter Dim AdapObj As OleDbDataAdapter = New OleDbDataAdapter() Create the object of

type OleDbCommand Dim DbCmd As New OleDbCommand() Set the CommandText property of the OleDbCommand object to the SQL

statement that uses the property procedure declared in the Standard module DbCmd.CommandText = Standard.SQLCommand Set

the Connection property of the OleDbCommand object to the OleDbConnection object, which the OleDbCommand object will use as


26/31

the data source connection for fetching the data DbCmd.Connection = Conn Set the SelectCommand property of the

OleDbDataAdapter object to the OleDbCommand object AdapObj.SelectCommand = DbCmd

In this code, AdapObj is the object of the OleDbDataAdapter class,and DbCmd is the object of the

OleDbCommand class. The CommandText property of the DbCmd object is set to the SQLCommand property

stored in the Standard module, and the Connection property of the DbCmd object is set to the Conn

object, which stores the connection information. Then, the SelectCommand property of the AdapObj

object is set to the DbCmd object.

As you know, you use the Fill()method of the OleDBDataAdapter class to fill the dataset with the

relevant data that is fetched from the database.This data is then displayed in the data grid on the

form. The code for the Fill() method is as follows:

Create an object of the type DataSet Dim DstObj As DataSet = New DataSet() Call the Fill method of the OleDbDataAdapter object to

fill the dataset AdapObj.Fill(DstObj, SalesTable) Store the result as the number of rows returned RowCount =

DstObj.Tables(SalesTable).Rows.Count Check the number of rows stored in the RowCount variable If RowCount > 0 Then If rows are

greater than 0, then the data is displayed in the datagrid control Label to display information LBLUserMsg.Text = For &




End If

In this code, an object (DstObj) of the dataset is created. Then, the Fill() method of the

OleDbDataAdapter class is called to fill the dataset with the relevant data.The dataset object and the

name of the table that will store the data are provided as parameters of the Fill() method. Here, for

the table name parameter, it is not necessary for the table name to be the same as it is in the

database. You can give any relevant name to the table. When the Fill() method is called, the

RowCount variable, which is declared as an integer, is used to store the count of rows that arereturned in the dataset as the result of the query executed.

An If ... Then construct is used for the code to bind the result to the data grid control. The If

statement of the construct checks whether the number of rows returned as the result is more

than zero. If the database contains records for the choices that the user selects on the main form,

then the Ifstatement will evaluate toTrue. In this case, the LBLUserMsg label displays the text For

and the value that is stored in the ControlValue property of the Standard module. The DstObj object is

specified in the DataSource property of the DataGrid control. The data in the dataset is binded to theDataGrid control by using the DataBind property. This indicates that the data from the dataset will be

displayed in the data grid. However, if the database does not contain any record for the selected

choices,then no rows will be fetched in the dataset. In that case, the Ifstatement evaluates to F a l


27/31

s e, and the E l s e statement of the con s t ruct exe c u t e s . Th e re f o re, t h e LBLUserMsg label will

display the text No Records Available. Once the required data is retrieved from the database,

the Conn object is used to call the Close() method, which closes the open connection to the

database.

After viewing the sales data, the user can click on the OKbutton on the form.This redirects the

user to the ViewSalesData.aspx page. The following is the code attached to the Click event of the

OKbutton:

Private Sub BtnOK_Click(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles BtnOK.Click

Redirect to the ViewSalesData page

R e s p o n s e . R e d i r e c t ( V i e w S a l e s D a t a . a s p x )

End Sub

The Complete Example Code

Now that you have learned about the code that enables the functioning of the SalesData

application, in this section I provide the complete code of the ViewSalesData.aspx and the

SalesData.aspx pages of the application. Listing 8-1 is the code of the ViewSalesData.aspx page,

and Listing 8-2 is the code of the SalesData.aspx page. These example files (Vi ew Sa l e s D a t a

. a s p x . vb and SalesData.aspx.vb) are included on the Web site www.premierpressbooks.com/

downloads.asp.

Listing 8-1 ViewSalesData.aspx.vb

Public Class WebForm1

Inherits System.Web.UI.Page

Protected WithEvents CalSales As System.Web.UI.WebControls.Calendar

Protected WithEvents DDLYear As System.Web.UI.WebControls.DropDownList Protected WithEvents DDLRegion As

System.Web.UI.WebControls.DropDownList Protected WithEvents BtnViewSales As System.Web.UI.WebControls.Button Protected

WithEvents LblRegion As System.Web.UI.WebControls.Label Protected WithEvents LblYear As System.Web.UI.WebControls.Label

Protected WithEvents LblDate As System.Web.UI.WebControls.Label Protected WithEvents RBDate As

System.Web.UI.WebControls.RadioButton Protected WithEvents RBYear As System.Web.UI.WebControls.RadioButton Protected

WithEvents BtnReset As System.Web.UI.WebControls.Button

#Region Web Form Designer Generated Code

This call is required by the Web Form Designer. Private Sub InitializeComponent()

End Sub


28/31

Private Sub Page_Init(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles MyBase.Init CODEGEN: This method call is required by the Web Form Designer Do not modify

it using the code editor. I n i t i a l i z e C o m p o n e n t ( )

End Sub

#End Region

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Put user code to initialize

the page here End Sub

Private Sub BtnViewSales_Click(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles BtnViewSales.Click Simple If loop to decide what SQL query to be executed according to the

selections made by the user


If DDLRegion.SelectedItem.Text = All Then SQL query to be stored in the SQLCommand property procedure of the Standard module

Standard.SQLCommand = SELECT [Product Code], [Product Name], [Units Sold], [Price ($)], [Total Sales ($)] FROM Sales Where [Date

of Sale] = & CalSales.SelectedDate.Date.ToShortDateString &

Value to be stored in the ControlValue property procedure

of the Standard module Standard.ControlValue = all the regions on & C a l S a l e s . S e l e c t e d D a t e . D a t e . T o S h o r t D a

t e S t r i n g


Region = & DDLRegion.SelectedItem.Text.Trim & and [Date of Sale] = & CalSales.SelectedDate & Standard.ControlValue =

the & DDLRegion.SelectedItem.Text & region on & CalSales.SelectedDate.Date.ToShortDateString

End If ElseIf CalSales.Visible = False And DDLYear.Visible = True Then


($)], [Total Sales ($)] FROM Sales Where Year([Date of Sale]) = & DDLYear.SelectedItem.Text & Standard.ControlValue = all the

regions in the year & D D L Y e a r . S e l e c t e d I t e m . T e x t

E l s e Standard.SQLCommand = SELECT [Product Code], [Product Name], [Units Sold], [Price ($)], [Total Sales ($)] FROM Sales WhereRegion = & DDLRegion.SelectedItem.Text.Trim & and Year([Date of Sale]) = & DDLYear.SelectedItem.Text &

Standard.ControlValue = the & DDLRegion.SelectedItem.Text & region in the year & DDLYear.SelectedItem.Text

End If End If

di h S l


29/31

Redirect to the SalesData page

R e s p o n s e . R e d i r e c t ( S a l e s D a t a . a s p x ) End Sub

Private Sub RBDate_CheckedChanged(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles RBDate.CheckedChanged Set the Visible property for the controls BtnViewSales.Visible = True

BtnReset.Visible = True LblYear.Visible = False LblDate.Visible = True RBDate.Visible = False CalSales.Visible = True RBYear.Visible =

False DDLYear.Visible = False

End Sub

Private Sub RBYear_CheckedChanged(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles RBYear.CheckedChanged Set the Visible property for the controls BtnViewSales.Visible = True

BtnReset.Visible = True LblYear.Visible = True LblDate.Visible = False RBYear.Visible = False CalSales.Visible = False RBDate.Visible =

False DDLYear.Visible = True

End If End Sub

Private Sub BtnReset_Click(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles BtnReset.Click Reload the page R e s p o n s e . R e d i r e c t ( V i e w S a l e s D a t a . a s p x

)

End Sub End Class

Listing 8-2 SalesData.aspx.vb

Imports System.Data.OleDb

Public Class SalesData Inherits System.Web.UI.Page Protected WithEvents LBLUserMsg As System.Web.UI.WebControls.Label Protected

WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid Protected WithEvents BtnOK As System.Web.UI.WebControls.Button

Create an object of the type OleDbConnection Dim Conn As OleDbConnection

#Region Web Form Designer Generated Code This call is required by the Web Form Designer.

Private Sub InitializeComponent() End Sub

Private Sub Page_Init(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles MyBase.Init CODEGEN: This method call is required by the Web Form Designer Do not modifyit using the code editor. I n i t i a l i z e C o m p o n e n t ( )

End Sub #End Region


30/31

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Try block is used for code

whose exceptions are handled by the catch block T r y

Declare an integer variable to validate the number of rows returned Dim RowCount As Integer Specify the connection string Conn =

New OleDbConnection(Provider=Microsoft.Jet.OLEDB.4.0; & _ Data source= & Request.PhysicalApplicationPath & /Sales.mdb;)

Open the connection C o n n . O p e n ( ) Create an object of the OleDbDataAdapter class and

pass the SQL command and the connection information as parameters Dim AdapObj As OleDbDataAdapter = New OleDbDataAdapter

(Standard.SQLCommand, Conn) Create an object of the type DataSet Dim DstObj As DataSet = New DataSet() Call the Fill method of

the OleDbDataAdapter object to fill the dataset AdapObj.Fill(DstObj, SalesTable) Store the result as the number of rows returned

RowCount = DstObj.Tables(SalesTable).Rows.Count Check the number of rows stored in the RowCount variable If RowCount > 0 Then

If rows are greater than 0, then the data is displayed in the datagrid control Label to display information LBLUserMsg.Text = For &




End If Catch block is basically used to trap all the exceptions/error information that might occur in executing the code in the try

block.

Catch RunException As Exception Declare a variable of the type exception Write the error message for the user reference

Response.Write(Error Occured: & vbLf & RunException.ToString) The cleanup code comes here

F i n a l l y Close the connection C o n n . C l o s e ( )

End Try End Sub

Private Sub BtnOK_Click(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles BtnOK.Click Redirect to the ViewSalesData page R e s p o n s e . R e d i r e c t ( V i e w S a l e

s D a t a . a s p x )

End Sub End Class

Summary

In this chapter, I showed you how to design the two forms used by the SalesData application. You

also learned about the working of the application. Next, you saw the code attached to the various

controls of the forms. Finally, you learned how the connection to the database is established and

how the data retrieved from the database is displayed to the users. In the next chapter, I explain

h t D t Ad t C fi ti Wi d t fi d t d t d il t bli h


31/31

how to use Data Adapter Configuration Wizard to configure a data adapter and easily establish

the connection with the database.

Documents

Webcontrols.calendar Select Year