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DetailsViewUpdateEventHandler-Delegat

Stellt die Methode dar, die das ItemUpdating-Ereignis eines DetailsView-Steuerelements behandelt.

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

public delegate void DetailsViewUpdateEventHandler (
	Object sender,
	DetailsViewUpdateEventArgs e
)
/** @delegate */
public delegate void DetailsViewUpdateEventHandler (
	Object sender, 
	DetailsViewUpdateEventArgs e
)
Nicht zutreffend.

Parameter

sender

Die Quelle des Ereignisses.

e

Eine Instanz von DetailsViewUpdateEventArgs, die die Ereignisdaten enthält.

Das DetailsView-Steuerelement löst das ItemUpdating-Ereignis aus, wenn innerhalb des Steuerelements auf eine Schaltfläche Aktualisieren geklickt wird (eine Schaltfläche, deren CommandName-Eigenschaft auf "Update" festgelegt wurde). Dabei wird das Ereignis ausgelöst, bevor das DetailsView-Steuerelement den Datensatz aktualisiert. Dadurch können Sie einen Ereignishandler bereitstellen, der beim Auftreten dieses Ereignisses eine benutzerdefinierte Routine ausführt, beispielsweise eine HTML-Codierung der Werte eines Datensatzes vor seinem Aktualisieren in der Datenquelle.

Beim Erstellen eines DetailsViewUpdateEventHandler-Delegaten geben Sie die Methode für die Ereignisbehandlung an. Fügen Sie dem Ereignis eine Instanz des Delegaten hinzu, um das Ereignis dem Ereignishandler zuzuordnen. Der Ereignishandler wird bei jedem Eintreten des Ereignisses aufgerufen, sofern der Delegat nicht entfernt wird. Weitere Informationen zu Ereignishandlerdelegaten finden Sie unter Ereignisse und Delegaten.

Im folgenden Codebeispiel wird veranschaulicht, wie dem ItemUpdating-Ereignis eines DetailsView-Steuerelements programmgesteuert ein DetailsViewUpdateEventHandler-Delegat hinzugefügt wird.


<%@ Page language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
  
  void Page_Load(Object sender, EventArgs e)
  {

    // Create a new DetailsView object.
    DetailsView customerDetailsView = new DetailsView();

    // Set the DetailsView object's properties.
    customerDetailsView.ID = "CustomerDetailsView";
    customerDetailsView.DataSourceID = "DetailsViewSource";
    customerDetailsView.AutoGenerateRows = true;
    customerDetailsView.AutoGenerateEditButton = true;
    customerDetailsView.AllowPaging = true;
    customerDetailsView.DataKeyNames = new String[1] { "CustomerID" };
    customerDetailsView.PagerSettings.Position = PagerPosition.Bottom;

    // Programmatically register the event-handling methods
    // for the DetailsView control.
    customerDetailsView.ItemUpdating 
      += new DetailsViewUpdateEventHandler(
      this.CustomerDetailsView_ItemUpdating);
    customerDetailsView.ModeChanging 
      += new DetailsViewModeEventHandler(
      this.CustomerDetailsView_ModeChanging);

    // Add the DetailsView object to the Controls collection
    // of the PlaceHolder control.
    DetailsViewPlaceHolder.Controls.Add(customerDetailsView);

  }
  
  void CustomerDetailsView_ItemUpdating(Object sender, 
    DetailsViewUpdateEventArgs e)
  {

    // Validate the field values entered by the user. This
    // example determines whether the user left any fields
    // empty. Use the NewValues property to access the new 
    // values entered by the user.
    ArrayList emptyFieldList = 
      ValidateFields((IOrderedDictionary)e.NewValues);

    if (emptyFieldList.Count > 0)
    {

      // The user left some fields empty. Display an error message.
      
      // Use the Keys property to retrieve the key field value.
      String keyValue = e.Keys["CustomerID"].ToString();

      MessageLabel.Text = 
        "You must enter a value for all fields of record " +
        keyValue + ".<br/>The following fields are missing:<br/><br/>";

      // Display the missing fields.
      foreach (String value in emptyFieldList)
      {
        // Use the OldValues property access the original value
        // of a field.
        MessageLabel.Text += value + " - Original Value = " + 
          e.OldValues[value].ToString() + "<br />";
      }

      // Cancel the update operation.
      e.Cancel = true;

    }
    else
    {
      // The field values passed validation. Clear the
      // error message label.
      MessageLabel.Text = "";
    }

  }

  ArrayList ValidateFields(IOrderedDictionary list)
  {
    
    // Create an ArrayList object to store the
    // names of any empty fields.
    ArrayList emptyFieldList = new ArrayList();

    // Iterate though the field values entered by
    // the user and check for an empty field. Empty
    // fields contain a null value.
    foreach (DictionaryEntry entry in list)
    {
      if (entry.Value == null)
      {
        // Add the field name to the ArrayList object.
        emptyFieldList.Add(entry.Key.ToString());
      }
    }

    return emptyFieldList;
  }

  void CustomerDetailsView_ModeChanging(Object sender, 
    DetailsViewModeEventArgs e)
  {
    if (e.CancelingEdit)
    {
      // The user canceled the update operation.
      // Clear the error message label.
      MessageLabel.Text = "";
    }
  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>DetailsViewUpdateEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>DetailsViewUpdateEventHandler Example</h3>
        
      <!-- Use a PlaceHolder control as the container for the -->
      <!-- dynamically generated DetailsView control.         -->       
      <asp:placeholder id="DetailsViewPlaceHolder"
        runat="server"/>
        
      <br/><br/>
      
      <asp:label id="MessageLabel"
        forecolor="Red"
        runat="server"/>
          
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value   -->
      <!-- from the web.config file.                            -->
      <asp:sqldatasource id="DetailsViewSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], 
          [City], [PostalCode], [Country] From [Customers]"
        updatecommand="Update [Customers] Set 
          [CompanyName]=@CompanyName, [Address]=@Address, 
          [City]=@City, [PostalCode]=@PostalCode, 
          [Country]=@Country 
          Where [CustomerID]=@CustomerID"
        connectionstring=
          "<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>
          
    </form>
  </body>
</html>


Im folgenden Codebeispiel wird veranschaulicht, wie dem ItemUpdating-Ereignis eines DetailsView-Steuerelements deklarativ ein DetailsViewUpdateEventHandler-Delegat hinzugefügt wird.


<%@ Page language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">
  
  void CustomerDetailsView_ItemUpdating(Object sender, 
    DetailsViewUpdateEventArgs e)
  {

    // Validate the field values entered by the user. This
    // example determines whether the user left any fields
    // empty. Use the NewValues property to access the new 
    // values entered by the user.
    ArrayList emptyFieldList = 
      ValidateFields((IOrderedDictionary)e.NewValues);

    if (emptyFieldList.Count > 0)
    {

      // The user left some fields empty. Display an error message.
      
      // Use the Keys property to retrieve the key field value.
      String keyValue = e.Keys["CustomerID"].ToString();

      MessageLabel.Text = 
        "You must enter a value for all fields of record " +
        keyValue + ".<br/>The following fields are missing:<br/><br/>";

      // Display the missing fields.
      foreach (String value in emptyFieldList)
      {
        // Use the OldValues property access the original value
        // of a field.
        MessageLabel.Text += value + " - Original Value = " + 
          e.OldValues[value].ToString() + "<br />";
      }

      // Cancel the update operation.
      e.Cancel = true;

    }
    else
    {
      // The field values passed validation. Clear the
      // error message label.
      MessageLabel.Text = "";
    }

  }

  ArrayList ValidateFields(IOrderedDictionary list)
  {
    
    // Create an ArrayList object to store the
    // names of any empty fields.
    ArrayList emptyFieldList = new ArrayList();

    // Iterate though the field values entered by
    // the user and check for an empty field. Empty
    // fields contain a null value.
    foreach (DictionaryEntry entry in list)
    {
      if (entry.Value == null)
      {
        // Add the field name to the ArrayList object.
        emptyFieldList.Add(entry.Key.ToString());
      }
    }

    return emptyFieldList;
  }

  void CustomerDetailsView_ModeChanging(Object sender, 
    DetailsViewModeEventArgs e)
  {
    if (e.CancelingEdit)
    {
      // The user canceled the update operation.
      // Clear the error message label.
      MessageLabel.Text = "";
    }
  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>DetailsViewUpdateEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>DetailsViewUpdateEventHandler Example</h3>
                       
      <asp:detailsview id="CustomerDetailsView"
        datasourceid="DetailsViewSource"
        autogeneraterows="true"
        autogenerateeditbutton="true"  
        allowpaging="true"
        datakeynames="CustomerID" 
        onitemupdating="CustomerDetailsView_ItemUpdating"
        onmodechanging="CustomerDetailsView_ModeChanging" 
        runat="server">
          
        <pagersettings position="Bottom"/> 
                  
      </asp:detailsview>
      
      <br/>
      
      <asp:label id="MessageLabel"
        forecolor="Red"
        runat="server"/>
          
      <!-- This example uses Microsoft SQL Server and connects  -->
      <!-- to the Northwind sample database. Use an ASP.NET     -->
      <!-- expression to retrieve the connection string value   -->
      <!-- from the web.config file.                            -->
      <asp:sqldatasource id="DetailsViewSource"
        selectcommand="Select [CustomerID], [CompanyName], [Address], 
          [City], [PostalCode], [Country] From [Customers]"
        updatecommand="Update [Customers] Set 
          [CompanyName]=@CompanyName, [Address]=@Address, 
          [City]=@City, [PostalCode]=@PostalCode, 
          [Country]=@Country 
          Where [CustomerID]=@CustomerID"
        connectionstring=
          "<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>
          
    </form>
  </body>
</html>


Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

Microsoft .NET Framework 3.0 wird unter Windows Vista, Microsoft Windows XP SP2 und Windows Server 2003 SP1 unterstützt.

.NET Framework

Unterstützt in: 3.0, 2.0
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