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WebPartTransformerAttribute Class

Identifies the types of connection points that a transformer supports.

Namespace:  System.Web.UI.WebControls.WebParts
Assembly:  System.Web (in System.Web.dll)

'Declaration
<AttributeUsageAttribute(AttributeTargets.Class)> _
<AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level := AspNetHostingPermissionLevel.Minimal)> _
Public NotInheritable Class WebPartTransformerAttribute _
	Inherits Attribute
'Usage
Dim instance As WebPartTransformerAttribute

Transformers are used to translate data between two Web Parts controls with incompatible connection points. Connection points are incompatible when they provide or consume data through different interfaces. For example, a provider implementing a provider connection point of type IWebPartRow could not directly connect to a consumer expecting a provider connection point of type IWebPartTable. Instead, a transformer must be used to connect the two connection points. A customized transformer can be created by deriving a class from the WebPartTransformer class.

The WebPartTransformerAttribute attribute is applied to a WebPartTransformer class. It defines the type of provider connection point and the type of consumer connection point that a transformer supports. The type of consumer and provider connection points supported by the transformer must match the connection points of the consumer and provider Web Parts controls for a connection to be made between the controls. At run time, the type of connection points that a particular transformer supports can be retrieved through the GetConsumerType and GetProviderType methods.

The following code example demonstrates the use of a WebPartTransformerAttribute attribute with a customized WebPartTransformer class. The attribute indicates that the RowToStringTransformer class can transform a provider connection point of type IWebPartRow to a consumer connection point of type IString.

This code example is part of a larger example found in the WebPartTransformer class overview.

' A transformer that transforms a row to a string.
<AspNetHostingPermission(SecurityAction.Demand, _
   Level:=AspNetHostingPermissionLevel.Minimal)> _
<AspNetHostingPermission(SecurityAction.InheritanceDemand, _
   Level:=AspNetHostingPermissionLevel.Minimal)> _
<WebPartTransformer(GetType(IWebPartRow), GetType(IString))> _
Public Class RowToStringTransformer
    Inherits WebPartTransformer
    Implements IString

    Private _provider As IWebPartRow
    Private _callback As StringCallback

    Private Sub GetRowData(ByVal rowData As Object)
        Dim props As PropertyDescriptorCollection = _provider.Schema

        If ((Not (props Is Nothing)) AndAlso (props.Count > 0) _
          AndAlso (Not (rowData Is Nothing))) Then 
            Dim returnValue As String = String.Empty
            For Each prop As PropertyDescriptor In props
                If Not (prop Is props(0)) Then
                    returnValue += ", " 
                End If
                returnValue += prop.DisplayName.ToString() + ": " + _
                    prop.GetValue(rowData).ToString()
            Next
            _callback(returnValue)
        Else
            _callback(Nothing)
        End If 
    End Sub 

    Public Overrides Function Transform(ByVal providerData As Object) As Object
        _provider = CType(providerData, IWebPartRow)
        Return Me 
    End Function 


    Sub GetStringValue(ByVal callback As StringCallback) _
       Implements IString.GetStringValue
        If (callback Is Nothing) Then 
            Throw New ArgumentNullException("callback")
        End If 

        If (Not (_provider Is Nothing)) Then
            _callback = callback
            _provider.GetRowData(New RowCallback(AddressOf GetRowData))
        Else
            callback(Nothing)
        End If 
    End Sub 
End Class

System.Object
  System.Attribute
    System.Web.UI.WebControls.WebParts.WebPartTransformerAttribute

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 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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