DataSourceDesigner Class

Provides design-time support in a design host for the DataSourceControl class.

Namespace: System.Web.UI.Design
Assembly: System.Design (in system.design.dll)

'Declaration
Public Class DataSourceDesigner
	Inherits ControlDesigner
	Implements IDataSourceDesigner
'Usage
Dim instance As DataSourceDesigner

public class DataSourceDesigner extends ControlDesigner implements IDataSourceDesigner
public class DataSourceDesigner extends ControlDesigner implements IDataSourceDesigner
Not applicable.

The DataSourceDesigner class is the base class for data source designers, such as the SqlDataSourceDesigner, AccessDataSourceDesigner, and ObjectDataSourceDesigner classes. If you create a new data source control, you might also want to create a custom control designer for your control and derive it from the DataSourceDesigner class.

The DataSourceDesigner class has two event methods: the OnDataSourceChanged and OnSchemaRefreshed methods. Both of these events can be temporarily disabled with the SuppressDataSourceEvents method, which sets the SuppressingDataSourceEvents property. The event methods can be enabled again with the ResumeDataSourceEvents method.

There are two static methods that you can use to evaluate the equivalency of schemas or views without creating an instance of the class:

Notes to Inheritors: To provide commands for the action list menu at design time in a derived class, you must override the ActionLists property to return a custom DesignerActionListCollection object with custom items that are derived from the DesignerActionList object.

The following code example shows how to use a custom data source control with several other small custom classes, as listed in the following table.

Custom class

Derived from

CustomDataSource

ObjectDataSource

CustomDataSourceDesigner

DataSourceDesigner

CustomDataSourceView

ObjectDataSourceView

CustomDesignDataSourceView

DesignerDataSourceView

BookListViewSchema

IDataSourceViewSchema

CustomIDFieldSchema

IDataSourceFieldSchema

CustomTitleFieldSchema

IDataSourceFieldSchema

BookItem (A two-field data structure.)

After compiling the code example, open the .aspx page in Design view and then set the DataSourceID property to the ID of the custom data source control.

Imports Microsoft.VisualBasic
Imports System
Imports System.Data
Imports System.Security.Permissions
Imports System.Collections
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls
Imports System.Web.UI.Design
Imports System.Web.UI.Design.WebControls
Imports System.ComponentModel
Imports System.ComponentModel.Design

Namespace ASPNet.Design.Samples_VB
    <Designer(GetType(CustomDataSourceDesigner)), _
        ToolboxData("<{0}:CustomDataSource runat=""server""></{0}:CustomDataSource>")> _
    Public Class CustomDataSource
        Inherits ObjectDataSource

        Dim _defaultViewName As String = "BookList"
        Dim _view As ObjectDataSourceView = Nothing

        Public Sub New()
            MyBase.New()
        End Sub

        ' Gets a view by name
        Protected Overrides Function GetView(ByVal viewName As String) As DataSourceView
            ' This data source only allows one view
            If Not (viewName.Equals(_defaultViewName)) Then
                Return Nothing
            ElseIf IsNothing(_view) Then
                _view = New CustomDataSourceView(Me, _
                    _defaultViewName, HttpContext.Current)
            End If

            Return _view
        End Function

        ' Gets a list of view names for this class
        Protected Overrides Function GetViewNames() As ICollection
            Dim ar As New ArrayList()
            ar.Add(_defaultViewName)
            Return CType(ar, ICollection)
        End Function

    End Class

    ' The runtime data source view
    Public Class CustomDataSourceView
        Inherits ObjectDataSourceView

        Dim _data As ArrayList = Nothing

        Public Sub New(ByVal owner As CustomDataSource, ByVal viewName As String, ByVal context As HttpContext)
            MyBase.New(owner, viewName, context)
            owner.SelectCountMethod = "GetCount"
        End Sub

        ' This method would typically get a set of live data
        ' rather than create some dummy data
        Protected Overrides Function ExecuteSelect(ByVal arguments As DataSourceSelectArguments) As System.Collections.IEnumerable
            If (IsNothing(_data)) Then
                _data = New ArrayList()
                _data.Add(New BookItem("ID_1", "Runtime Title 01"))
                _data.Add(New BookItem("ID_2", "Runtime Title 02"))
                _data.Add(New BookItem("ID_3", "Runtime Title 03"))
            End If
            Return CType(_data, IEnumerable)
        End Function

        ' Allow getting the record count
        Public Overrides ReadOnly Property CanRetrieveTotalRowCount() As Boolean
            Get
                Return True
            End Get
        End Property

        ' Returns the number of records in the current set of data
        Public ReadOnly Property GetCount() As Integer
            Get
                If IsNothing(_data) Then
                    Return 0
                Else
                    Return _data.Count
                End If
            End Get
        End Property
        ' Do not allow deletions
        Public Overrides ReadOnly Property CanDelete() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow insertions
        Public Overrides ReadOnly Property CanInsert() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow paging
        Public Overrides ReadOnly Property CanPage() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow sorting
        Public Overrides ReadOnly Property CanSort() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow updating
        Public Overrides ReadOnly Property CanUpdate() As Boolean
            Get
                Return False
            End Get
        End Property

    End Class

    ' A class to define a record of the data
    Public Class BookItem
        Private _id As String
        Private _title As String

        Public Sub New(ByVal id As String, ByVal title As String)
            _id = id
            _title = title
        End Sub

        Public ReadOnly Property ID() As String
            Get
                Return _id
            End Get
        End Property

        Public Property Title() As String
            Get
                Return _title
            End Get
            Set(ByVal value As String)
                _title = value
            End Set
        End Property
    End Class

    ' Custom designer for the CustomDataSource control.
    Public Class CustomDataSourceDesigner
        Inherits DataSourceDesigner

        Private _control As CustomDataSource = Nothing
        Private _defaultViewName As String = "BookList"
        Private _view As CustomDesignDataSourceView = Nothing

        Public Overrides Sub Initialize(ByVal cmponent As IComponent)
            MyBase.Initialize(cmponent)
            _control = CType(cmponent, CustomDataSource)
        End Sub

        ' Get a view
        Public Overrides Function GetView(ByVal viewName As String) As DesignerDataSourceView
            If Not (viewName.Equals(_defaultViewName)) Then
                Return Nothing
            ElseIf IsNothing(_view) Then
                _view = New CustomDesignDataSourceView(Me, _
                    _defaultViewName)
            End If

            Return _view
        End Function

        ' Get a list of view names
        Public Overrides Function GetViewNames() As String()
            Return New String() {"BookList"}
        End Function

        ' Don't allow refreshing the schema
        Public Overrides ReadOnly Property CanRefreshSchema() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow resizing
        Public Overrides ReadOnly Property AllowResize() As Boolean
            Get
                Return False
            End Get
        End Property
    End Class

    ' A     design-time data source view
    Public Class CustomDesignDataSourceView
        Inherits DesignerDataSourceView

        Private _data As ArrayList = Nothing

        Public Sub New(ByVal owner As CustomDataSourceDesigner, ByVal viewName As String)
            MyBase.New(owner, viewName)
        End Sub

        ' Get data for design-time display
        Public Overrides Function GetDesignTimeData( _
            ByVal minimumRows As Integer, _
            ByRef isSampleData As Boolean) As IEnumerable

            If IsNothing(_data) Then
                ' Create a set of design-time fake data
                _data = New ArrayList()
                Dim i As Integer
                For i = 1 To minimumRows
                    _data.Add(New BookItem("ID_" & i.ToString(), _
                        "Design-Time Title 0" & i.ToString()))
                Next
            End If
            isSampleData = True
            Return CType(_data, IEnumerable)
        End Function

        Public Overrides ReadOnly Property Schema() As IDataSourceViewSchema
            Get
                Return New BookListViewSchema()
            End Get
        End Property

        ' Allow getting the record count
        Public Overrides ReadOnly Property CanRetrieveTotalRowCount() As Boolean
            Get
                Return True
            End Get
        End Property
        ' Do not allow deletions
        Public Overrides ReadOnly Property CanDelete() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow insertions
        Public Overrides ReadOnly Property CanInsert() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow updates
        Public Overrides ReadOnly Property CanUpdate() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow paging
        Public Overrides ReadOnly Property CanPage() As Boolean
            Get
                Return False
            End Get
        End Property
        ' Do not allow sorting
        Public Overrides ReadOnly Property CanSort() As Boolean
            Get
                Return False
            End Get
        End Property
    End Class

    ' A custom View Schema class
    Public Class BookListViewSchema
        Implements IDataSourceViewSchema

        Public Sub New()
        End Sub

        ' The name of this View Schema
        Public ReadOnly Property Name() As String Implements IDataSourceViewSchema.Name
            Get
                Return "BookList"
            End Get
        End Property

        ' Build a Field Schema array
        Public Function GetFields() As IDataSourceFieldSchema() Implements IDataSourceViewSchema.GetFields
            Dim fields(1) As IDataSourceFieldSchema
            fields(0) = New CustomIDFieldSchema()
            fields(1) = New CustomTitleFieldSchema()
            Return fields
        End Function
        ' There are no child views, so return Nothing
        Public Function GetChildren() As IDataSourceViewSchema() Implements IDataSourceViewSchema.GetChildren
            Return Nothing
        End Function
    End Class

    ' A custom Field Schema class for ID
    Public Class CustomIDFieldSchema
        Implements IDataSourceFieldSchema

        Public Sub New()
        End Sub

        ' Name is ID
        Public ReadOnly Property Name() As String Implements IDataSourceFieldSchema.Name
            Get
                Return "ID"
            End Get
        End Property
        ' Data type is string
        Public ReadOnly Property DataType() As Type Implements IDataSourceFieldSchema.DataType
            Get
                Return GetType(String)
            End Get
        End Property
        ' This is not an Identity field
        Public ReadOnly Property Identity() As Boolean Implements IDataSourceFieldSchema.Identity
            Get
                Return False
            End Get
        End Property
        ' This field is read only
        Public ReadOnly Property IsReadOnly() As Boolean Implements IDataSourceFieldSchema.IsReadOnly
            Get
                Return True
            End Get
        End Property
        ' This field is unique
        Public ReadOnly Property IsUnique() As Boolean Implements IDataSourceFieldSchema.IsUnique
            Get
                Return True
            End Get
        End Property
        ' This field can't be longer than 20
        Public ReadOnly Property Length() As Integer Implements IDataSourceFieldSchema.Length
            Get
                Return 20
            End Get
        End Property
        ' This field can't be null
        Public ReadOnly Property Nullable() As Boolean Implements IDataSourceFieldSchema.Nullable
            Get
                Return False
            End Get
        End Property
        ' This is a Primary Key
        Public ReadOnly Property PrimaryKey() As Boolean Implements IDataSourceFieldSchema.PrimaryKey
            Get
                Return True
            End Get
        End Property

        ' These properties do not apply
        Public ReadOnly Property Precision() As Integer Implements IDataSourceFieldSchema.Precision
            Get
                Return -1
            End Get
        End Property
        Public ReadOnly Property Scale() As Integer Implements IDataSourceFieldSchema.Scale
            Get
                Return -1
            End Get
        End Property
    End Class

    ' A custom Field Schema class for Title
    Public Class CustomTitleFieldSchema
        Implements IDataSourceFieldSchema

        Public Sub New()
        End Sub

        ' Name is Title
        Public ReadOnly Property Name() As String Implements IDataSourceFieldSchema.Name
            Get
                Return "Title"
            End Get
        End Property
        ' Type is string
        Public ReadOnly Property DataType() As Type Implements IDataSourceFieldSchema.DataType
            Get
                Return GetType(String)
            End Get
        End Property
        ' This is not an Identity field
        Public ReadOnly Property Identity() As Boolean Implements IDataSourceFieldSchema.Identity
            Get
                Return False
            End Get
        End Property
        ' This field is not read only
        Public ReadOnly Property IsReadOnly() As Boolean Implements IDataSourceFieldSchema.IsReadOnly
            Get
                Return False
            End Get
        End Property
        ' This field is not unique
        Public ReadOnly Property IsUnique() As Boolean Implements IDataSourceFieldSchema.IsUnique
            Get
                Return False
            End Get
        End Property
        ' This field can't be longer than 100
        Public ReadOnly Property Length() As Integer Implements IDataSourceFieldSchema.Length
            Get
                Return 100
            End Get
        End Property
        ' This field can't be null
        Public ReadOnly Property Nullable() As Boolean Implements IDataSourceFieldSchema.Nullable
            Get
                Return False
            End Get
        End Property
        ' This is not the Primary Key
        Public ReadOnly Property PrimaryKey() As Boolean Implements IDataSourceFieldSchema.PrimaryKey
            Get
                Return False
            End Get
        End Property

        ' These properties do not apply
        Public ReadOnly Property Precision() As Integer Implements IDataSourceFieldSchema.Precision
            Get
                Return -1
            End Get
        End Property
        Public ReadOnly Property Scale() As Integer Implements IDataSourceFieldSchema.Scale
            Get
                Return -1
            End Get
        End Property
    End Class

End Namespace

	...

<%@ Page Language="VB" %>
<%@ Register TagPrefix="aspSample" 
    Namespace="ASPNet.Design.Samples_VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    
    <aspSample:CustomDataSource runat="server" 
        ID="CustomDS1"></aspSample:CustomDataSource>
    <asp:GridView ID="GridView1" runat="server"></asp:GridView>
    
    </div>
    </form>
</body>
</html>

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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