IPostBackDataHandler Interfaccia

Definizione

Definisce i metodi che i controlli server ASP.NET devono implementare per caricare automaticamente i dati di postback.Defines methods that ASP.NET server controls must implement to automatically load postback data.

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

Esempi

Nell'esempio di codice seguente viene illustrato un controllo server della casella di testo IPostBackDataHandler personalizzato che implementa l'interfaccia.The following code example demonstrates a custom text box server control that implements the IPostBackDataHandler interface. La Text proprietà viene modificata in seguito al postback e il controllo server genera un TextChanged evento dopo il caricamento dei dati di postback.The Text property is changed as a result of the postback, and the server control raises a TextChanged event after postback data has been loaded.

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

Commenti

È necessario implementare l' IPostBackDataHandler interfaccia quando si crea un controllo server che deve esaminare i dati del modulo di cui è stato eseguito il postback al server da parte del client.You must implement the IPostBackDataHandler interface when creating a server control that needs to examine form data that is posted back to the server by the client. Il contratto definito da questa interfaccia consente a un controllo server di determinare se lo stato deve essere modificato in seguito al postback e di generare gli eventi appropriati.The contract that this interface defines allows a server control to determine whether its state should be altered as a result of the postback, and to raise the appropriate events. Per ulteriori informazioni, vedere gestione degli eventi del server nelle pagine Web form ASP.NET.For more information, see Server Event Handling in ASP.NET Web Forms Pages.

Metodi

LoadPostData(String, NameValueCollection)

Quando viene implementato da una classe, elabora i dati di postback per un controllo server ASP.NET.When implemented by a class, processes postback data for an ASP.NET server control.

RaisePostDataChangedEvent()

Quando viene implementato da una classe, segnala al controllo server di notificare all'applicazione ASP.NET che lo stato del controllo è stato modificato.When implemented by a class, signals the server control to notify the ASP.NET application that the state of the control has changed.

Si applica a

Vedi anche