DEV397

Windows Forms Databinding

Mike Henderlight

Program Manager

Windows Forms

Microsoft Corporation

Agenda

Introduction

Basics

Writing a data source

Databinding Goals

Enable databinding to anything:Lists

Indexed Collections (IList)

DataSets

Data Items Business objects

*Any* object

Make Control Development easier /more consistent

Assumptions

“Three tier” is the driving scenarioDisconnected data

Finite numbers of records

Datasources all shareIndexable collections

Consistent programming model

Each List is homogeneous

ExamplesDataSet

Web Service returning an array of objects

Basics. . .

What is databinding?

Automatic display & update of dataReduces the amount of “boilerplate” code you have to write

Change notificationAutomatically updating data source from controls

Automatically updating controls from datasource

Managing the "current item"

Types of databinding

“Simple databinding”Property to property

Control has no knowledge of bindingStandard across all controls

Example: TextBox1.Text to Customer.Name

“Complex databinding”Binding to the List

Control has knowledge of binding Control dependent

Example: DataGrid1.DataSource = Customers

Types of DatasourceArray

No change notification so:No Add/DeleteLimited update

Assumes "binding type" is array type

IList (ArrayList, CollectionBase)No change notification so:

No Add/DeleteLimited update

Assumes "binding type" is:indexed accessor type or first item in the list type

Dim customers() As CustomerDim customers() As Customer

public Customer this[int index] { get; }public Customer this[int index] { get; }Default Public ReadOnly Property Item(index As Integer) As Default Public ReadOnly Property Item(index As Integer) As CustomerCustomer

Types of Datasource

IBindingListChange Notification so:

Add

Delete

Update

Sorting

Searching

Example: DataView

Binding Managers

CurrencyManagerManages binding for a list Manages the "current" item Raises CurrentChanged and PositionChanged eventsControls get “bindable list” from CurrencyManagerPoint of "consumer access"

PropertyManagerSimilar to CurrencyManager but for single object

Binding Managers

BindingContext Manages CurrencyManagers and PropertyManagers

Typically for a Form

For all contained controls

Creates CurrencyManagers and PropertyManagers

On demand based on a DataSource and a DataMember

Controls get CurrencyManager from BindingContext

Manages hierarchical relationships Based on DataMember

Enables Master-Details

44SetSet

22

SetSet

BindingContext

CurrencyManager

Binding

How it works. . .

DataSource

Customers[0].Name = “Bill”Customers[0].Name = “Bill”

11TextChangedTextChanged

22

ValidatedValidated

33SetSet

22ChangedChanged

11 SetSet

33

CurrentChangedCurrentChanged

11

What do you care about?Datasource: Property/ListChanged event

Causes control value to update

Control: PropertyChanged event Causes Binding to be marked as dirty

Control: Validated event Causes new value to be pushed to data source Can stop this using CausesValidation property

BindingContext:Get CurrencyManager for DataSource/DataMember

CurrencyManager:Position: Changes current itemBegin/End/CancelCurrent: Controls update of datasourceList: Get the data sourceCurrent: Get the "current item"CurrentChanged/Position Changed events

Binding BasicsBinding Basics

Using the Using the CurrencyManagerCurrencyManager

demodemo

Tips and Tricks

BindingContext:DataSource/DataMember is a key Different DS/DM means different CurrencyManager

Validation:Driven by Leave eventDoes happen for Menus, ToolbarCan force using Form.Validate

EndCurrentEdit:Required to flush datasource

Me.BindingManager(dataSet1, “Customers”)Me.BindingManager(dataSet1, “Customers”)DOES NOT EQUAL DOES NOT EQUAL

Me.BindingManager(dataSet1.Customers)Me.BindingManager(dataSet1.Customers)

Master-Details (DataSet)

Dataset: Bind thro’ the relationships:

BindingContext creates a RelatedCurrencyManager

DataGrid1.DataSource = DataSet1DataGrid1.DataSource = DataSet1DataGrid1.DataMember = “Customers”DataGrid1.DataMember = “Customers”

DataGrid2.DataSource = DataSet1DataGrid2.DataSource = DataSet1DataGrid2.DataMember = “Customers.CustOrders” DataGrid2.DataMember = “Customers.CustOrders”

DataGrid1.DataSource = DataSet1DataGrid1.DataSource = DataSet1DataGrid1.DataMember = _ DataGrid1.DataMember = _ “ “Customers.CustOrders.OrderOrderItems”Customers.CustOrders.OrderOrderItems”

Customers

Orders

OrderItems

CustOrdersCustOrders

OrderOrderItemsOrderOrderItems

Master-Details (Objects)

List: Bind thro’ the property names:

BindingContext creates a RelatedCurrencyManager

DataGrid1.DataSource = MyCustomersListDataGrid1.DataSource = MyCustomersListDataGrid1.DataMember = “Customers”DataGrid1.DataMember = “Customers”

DataGrid2.DataSource = MyCustomersListDataGrid2.DataSource = MyCustomersListDataGrid2.DataMember = “Customers.Orders” DataGrid2.DataMember = “Customers.Orders”

DataGrid1.DataSource = MyCustomersListDataGrid1.DataSource = MyCustomersListDataGrid1.DataMember = “Customers.Orders.OrderItems”DataGrid1.DataMember = “Customers.Orders.OrderItems”

Customers

Orders(OrdersCollection)

OrderItems(OrderItemsCollection)

Master-DetailsMaster-Details

demodemo

Lookup table

You can use a ComboBox or ListBox as a “lookup” table

Example: State field in Customer objectBind ComboBox to States collection

Set DisplayValue to “value” property name

Bind SelectedValue to Customer.State

ComboBox1.DataSource = MyStatesComboBox1.DataSource = MyStatesComboBox1.DisplayMember = “LongName”ComboBox1.DisplayMember = “LongName”ComboBox1.ValueMember = “ShortName”ComboBox1.ValueMember = “ShortName”

ComboBox1.DataBindings.Add _ComboBox1.DataBindings.Add _ (“SelectedValue”, DataSet1, “Customers.State”)(“SelectedValue”, DataSet1, “Customers.State”)

Lookup TableLookup Table

demodemo

Formatting

Example: Format 12 as $12.00

Use the Format and Parse events on the Binding:

Format and Parse are “paired” You need to do both

Use BCL Formatting to actually format the value

AddHandler TextBox1.DataBindings("Text").Format, _AddHandler TextBox1.DataBindings("Text").Format, _ AddressOf Me.TextBox1_FormatAddressOf Me.TextBox1_Format

textBox1.DataBindings["Text"].Format textBox1.DataBindings["Text"].Format +=new ConvertEventHandler(Form1_Format);+=new ConvertEventHandler(Form1_Format);

FormattingFormatting

demodemo

Displaying errors

You can set errors on the DataSet:

Use ErrorProvider to display this information

DataGrid automatically displays this information

Use IDataErrorInfo on your business objects

TIP: Don’t throw exceptions. We eat them!

row.RowError = "You need to update the Widget price"row.RowError = "You need to update the Widget price"row.SetColumnError("WidgetPrice", “Bad Widget Price")row.SetColumnError("WidgetPrice", “Bad Widget Price")

Displaying ErrorsDisplaying Errors

demodemo

Tips and Tricks (2)

Datasets:You always bind to a DataView but not to the DefaultView

The DataSet generates them on demand

You can get to the DataView thro’ the CurrencyManager

Use a DataViewManager to apply default Sorts and Filters

Esp. useful for “child views” in a Master-Details Form

Using a Using a DataViewManagerDataViewManager

demodemo

Writing a Data Source. . .

Datasource InterfacesData Lists

IList – indexed list

IBindingList – list that supports change events

searchable

sortable

IListSource – object that returns a list

ITypedList – list with schema

Data ItemsIEditableObject – Commit/Cancel

IDataErrorInfo – error information

ICustomTypeDescriptor – custom type information

IBindingListWe will focus on change notification, Add, Remove, Update:

public interface IBindingList : IList { public interface IBindingList : IList { // Properties // Properties bool bool AllowEditAllowEdit { get; } { get; } bool bool AllowNewAllowNew { get; } { get; } bool bool AllowRemoveAllowRemove { get; } { get; }. . . . . . bool bool SupportsChangeNotificationSupportsChangeNotification { get; } { get; }. . . . . . // Events // Events public event ListChangedEventHandler public event ListChangedEventHandler ListChangedListChanged;;

// Methods // Methods. . .. . . object object AddNewAddNew();();. . .. . .}}

Writing a custom Writing a custom data sourcedata source

demodemo

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