WebPartTransformerAttribute Class
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Identifies the types of connection points that a transformer supports.
public ref class WebPartTransformerAttribute sealed : Attribute
[System.AttributeUsage(System.AttributeTargets.Class)]
public sealed class WebPartTransformerAttribute : Attribute
[<System.AttributeUsage(System.AttributeTargets.Class)>]
type WebPartTransformerAttribute = class
inherit Attribute
Public NotInheritable Class WebPartTransformerAttribute
Inherits Attribute
- Inheritance
- Attributes
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(typeof(IWebPartRow), typeof(IString))]
public class RowToStringTransformer : WebPartTransformer, IString
{
private IWebPartRow _provider;
private StringCallback _callback;
private void GetRowData(object rowData)
{
PropertyDescriptorCollection props = _provider.Schema;
if (props != null && props.Count > 0 && rowData != null)
{
string returnValue = String.Empty;
foreach (PropertyDescriptor prop in props)
{
if (prop != props[0])
{
returnValue += ", ";
}
returnValue += prop.DisplayName + ": " + prop.GetValue(rowData);
}
_callback(returnValue);
}
else
{
_callback(null);
}
}
public override object Transform(object providerData)
{
_provider = (IWebPartRow)providerData;
return this;
}
void IString.GetStringValue(StringCallback callback)
{
if (callback == null)
{
throw new ArgumentNullException("callback");
}
if (_provider != null)
{
_callback = callback;
_provider.GetRowData(new RowCallback(GetRowData));
}
else
{
callback(null);
}
}
}
' 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
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.
Web |
Initializes a new instance of the WebPartTransformerAttribute class. |
Consumer |
Gets the Type of the interface supported by the consumer connection point. |
Provider |
Gets the Type of the interface supported by the provider connection point. |
Type |
When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute) |
Equals(Object) |
Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute) |
Get |
Returns the consumer type a transformer can accept on a connection point. |
Get |
Returns the hash code for this instance. (Inherited from Attribute) |
Get |
Returns the provider type a transformer can accept on a connection point. |
Get |
Gets the Type of the current instance. (Inherited from Object) |
Is |
When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute) |
Match(Object) |
When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute) |
Memberwise |
Creates a shallow copy of the current Object. (Inherited from Object) |
To |
Returns a string that represents the current object. (Inherited from Object) |
_Attribute. |
Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute) |
_Attribute. |
Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute) |
_Attribute. |
Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute) |
_Attribute. |
Provides access to properties and methods exposed by an object. (Inherited from Attribute) |
Prodotto | Versioni |
---|---|
.NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
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