IPostBackDataHandler 介面

  • 參考

定義

命名空間:
System.Web.UI
組件:
System.Web.dll

定義 ASP.NET 伺服器控制項必須實作的方法，以自動載入回傳資料。

public interface class IPostBackDataHandler
public interface IPostBackDataHandler
type IPostBackDataHandler = interface
Public Interface IPostBackDataHandler
衍生

範例

下列程式代碼範例示範實作 介面的 IPostBackDataHandler 自定義文本框伺服器控件。 屬性 Text 會隨著回傳而變更，而伺服器控件會在 TextChanged 載入回傳數據之後引發事件。

using System;
using System.Web;
using System.Web.UI;
using System.Collections;
using System.Collections.Specialized;

namespace CustomWebFormsControls {

   [System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")]
   public class MyTextBox: Control, IPostBackDataHandler {

      public String Text {
         get {
            return (String) ViewState["Text"];
         }

         set {
            ViewState["Text"] = value;
         }
      }

      public event EventHandler TextChanged;

      public virtual bool LoadPostData(string postDataKey,
         NameValueCollection postCollection) {

         String presentValue = Text;
         String postedValue = postCollection[postDataKey];

         if (presentValue == null || !presentValue.Equals(postedValue)) {
            Text = postedValue;
            return true;
         }

         return false;
      }

      public virtual void RaisePostDataChangedEvent() {
         OnTextChanged(EventArgs.Empty);
      }

      protected virtual void OnTextChanged(EventArgs e) {
         if (TextChanged != null)
            TextChanged(this,e);
      }

      protected override void Render(HtmlTextWriter output) {
         output.Write("<INPUT type= text name = "+this.UniqueID
            + " value = " + this.Text + " >");
      }
   }
}

Imports System.Web
Imports System.Web.UI
Imports System.Collections
Imports System.Collections.Specialized

Namespace CustomWebFormsControls
    
    <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> Public Class MyTextBox
        Inherits Control
        Implements IPostBackDataHandler
        
        
        Public Property Text() As String
            Get
                Return CType(Me.ViewState("Text"), String)
            End Get
            
            Set
                Me.ViewState("Text") = value
            End Set
        End Property
        
        
        Public Event TextChanged As EventHandler
        
        
        Public Overridable Shadows Function LoadPostData( _
        postDataKey As String, _
        postCollection As System.Collections.Specialized.NameValueCollection) _
        As Boolean Implements IPostBackDataHandler.LoadPostData
            
            Dim presentValue As String = Text
            Dim postedValue As String = postCollection(postDataKey)
            
            If presentValue Is Nothing Or Not presentValue.Equals(postedValue) Then
                Text = postedValue
                Return True
            End If
            
            Return False
        End Function
        
        
        Public Overridable Shadows Sub RaisePostDataChangedEvent() _
        Implements IPostBackDataHandler.RaisePostDataChangedEvent
        
            OnTextChanged(EventArgs.Empty)
        End Sub
        
        
        Protected Overridable Sub OnTextChanged(e As EventArgs)
            RaiseEvent TextChanged(Me, e)
        End Sub
        
        
        Protected Overrides Sub Render(output As HtmlTextWriter)
            output.Write("<INPUT type= text name = " & Me.UniqueID & _
                " value = " & Me.Text & " >")
        End Sub
        
    End Class
    
End Namespace

備註

您必須在 IPostBackDataHandler 建立需要檢查用戶端傳回伺服器之表單資料的伺服器控制項時實作 介面。 這個介面定義的合約可讓伺服器控件判斷其狀態是否應該因回傳而改變，以及引發適當的事件。 如需詳細資訊，請參閱 ASP.NET Web Forms 頁面中的伺服器事件處理。

方法

LoadPostData(String, NameValueCollection)

在類別實作時，處理 ASP.NET 伺服器控制項的回傳資料。
RaisePostDataChangedEvent()

當類別實作時，發出信號給伺服器控制項，使其告知 ASP.NET 應用程式，控制項的狀態已變更。

適用於

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