WebPartTransformerAttribute 類別

定義

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

繼承

Object

Attribute

WebPartTransformerAttribute

屬性

AttributeUsageAttribute

範例

以下程式碼範例示範了屬性與自訂WebPartTransformerAttribute類別的使用WebPartTransformer方式。 屬性表示該 RowToStringTransformer 類別可以將提供者 IWebPartRow 連線點 轉換為 型別 IString為 的消費者連線點。

此程式碼範例是類別概述中更大範例 WebPartTransformer 的一部分。

// 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

備註

轉換器用於在兩個不相容連接點的 Web Parts 控制項間轉換資料。 當連接點透過不同介面提供或消耗資料時，它們就不相容。 例如，一個實作提供者連接點為 的 IWebPartRow 提供者，無法直接連接到預期提供者連接點為 IWebPartTable的消費者。 取而代之的是，必須使用變壓器來連接兩個連接點。 可透過從類別 WebPartTransformer 衍生類別來建立自訂轉換器。

屬性 WebPartTransformerAttribute 是套用到 WebPartTransformer 類別上的。 它定義了供應商連接點的類型以及變壓器所支援的消費者連接點類型。 變壓器所支援的消費者與提供者連接點類型必須與消費者與提供者的網頁零件控制點相匹配，才能在控制點間建立連接。 執行時，可以透過 and GetConsumerType 方法取得GetProviderType特定變壓器所支援的連接點類型。