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FormViewDeleteEventHandler-Delegat

 

Veröffentlicht: Oktober 2016

Stellt die Methode zur Behandlung der ItemDeleting -Ereignis ein FormView Steuerelement.

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

public delegate void FormViewDeleteEventHandler(
	object sender,
	FormViewDeleteEventArgs e
)

Parameter

sender
Type: System.Object

Die Quelle des Ereignisses.

e
Type: System.Web.UI.WebControls.FormViewDeleteEventArgs

Ein FormViewDeleteEventArgs, das die Ereignisdaten enthält.

Die FormView -Steuerelement löst die ItemDeleting -Ereignis, wenn eine Schaltfläche zum Löschen (eine Schaltfläche mit der CommandName -Eigenschaft auf "Löschen") innerhalb des Steuerelements geklickt wird, jedoch bevor die FormView Steuerelement löscht den Datensatz. Dadurch können Sie eine Ereignisbehandlungsmethode bereitstellen, die eine benutzerdefinierte Routine ausführt, z. B. das Überprüfen eines Datensatzes, vor dem Löschen, wenn dieses Ereignis auftritt.

Beim Erstellen eines FormViewDeleteEventHandler-Delegaten bestimmen Sie die Methode für die Ereignisbehandlung. Um dem Ereignishandler das Ereignis zuzuordnen, fügen Sie dem Ereignis eine Instanz des Delegaten hinzu. Der Ereignishandler wird bei jedem Eintreten des Ereignisses aufgerufen, sofern der Delegat nicht entfernt wird. Weitere Informationen über Delegaten für Ereignishandler finden Sie unter NIB: Ereignisse und Delegaten.

Im folgenden Beispiel wird veranschaulicht, wie Sie programmgesteuert hinzufügen ein FormViewDeleteEventHandler zum Delegieren der ItemDeleting -Ereignis ein FormView Steuerelement.


<%@ page language="C#" %>
<%@ import namespace="System.Data"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  // To dynamically create a template for a FormView control,
  // you must create a custom template class to represent 
  // the template. This template class represents the item
  // template for a FormView control.
  private sealed class EmployeeTemplate : ITemplate
  {

    // When implementing the ITemplate interface, you must
    // implement the InstantiateIn method. The FormView
    // control calls this method to create the template's 
    // content. 
    void ITemplate.InstantiateIn(Control container)
    {
      // Create the child controls contained in the template.
      // For this example, the item template displays the
      // FirstName, LastName, and Title fields from the data 
      // source. To support data-binding, create event handlers 
      // for the DataBinding event of each child control.
      // The event handlers must bind the appropriate value 
      // to each control.
      Label firstNameLabel = new Label();
      firstNameLabel.ID = "FirstNameLabel";
      firstNameLabel.DataBinding += new EventHandler(FirstNameLabel_DataBinding);

      Label lastNameLabel = new Label();
      lastNameLabel.ID = "LastNameLabel";
      lastNameLabel.DataBinding += new EventHandler(LastNameLabel_DataBinding);

      Label titleNameLabel = new Label();
      titleNameLabel.ID = "TitleLabel";
      titleNameLabel.DataBinding += new EventHandler(TitleLabel_DataBinding);

      LiteralControl space = new LiteralControl("&nbsp;");
      LiteralControl titleLineBreak = new LiteralControl("<br/>");
      LiteralControl buttonLineBreak = new LiteralControl("<br/>");

      Button deleteButton = new Button();
      deleteButton.ID = "DeleteButton";
      deleteButton.CommandName = "Delete";
      deleteButton.Text = "Delete";

      // Add the controls to the Controls collection of the 
      // container control.
      container.Controls.Add(firstNameLabel);
      container.Controls.Add(space);
      container.Controls.Add(lastNameLabel);
      container.Controls.Add(titleLineBreak);
      container.Controls.Add(titleNameLabel);
      container.Controls.Add(buttonLineBreak);
      container.Controls.Add(deleteButton);

    }

    // This event handler binds the value of the FirstName field
    // to the FirstNameLabel Label control displayed in the template.
    private void FirstNameLabel_DataBinding(Object sender, EventArgs e)
    {
      // Use the sender parameter to retrieve the Label control
      // being bound to data.
      Label firstNameLabelControl = (Label)sender;

      // Retrieve the value to bind to the Label control. First,
      // use the NamingContainer property to retrieve the parent 
      // control of the Label control. In this example, the parent 
      // control is the FormView control.
      FormView formViewContainer = (FormView)firstNameLabelControl.NamingContainer;

      // Get the data item bound to the FormView control.
      DataRowView rowView = (DataRowView)formViewContainer.DataItem;

      // Use the data item to retrieve the value of the FirstName field.
      // Set the Text property of the Label control to this value.        
      firstNameLabelControl.Text = rowView["FirstName"].ToString();
    }

    // This event handler binds the value of the LastName field
    // to the LastNameLabel Label control displayed in the template.
    private void LastNameLabel_DataBinding(Object sender, EventArgs e)
    {
      // Use the sender parameter to retrieve the Label control
      // being bound to data.
      Label lastNameLabelControl = (Label)sender;

      // Retrieve the value to bind to the Label control. First,
      // use the NamingContainer property to retrieve the parent 
      // control of the Label control. In this example, the parent 
      // control is the FormView control.
      FormView formViewContainer = (FormView)lastNameLabelControl.NamingContainer;

      // Get the data item bound to the FormView control.
      DataRowView rowView = (DataRowView)formViewContainer.DataItem;

      // Use the data item to retrieve the value of the LastName field.
      // Set the Text property of the Label control to this value.         
      lastNameLabelControl.Text = rowView["LastName"].ToString();
    }

    // This event handler binds the value of the Title field
    // to the TitleLabel Label control displayed in the template.
    private void TitleLabel_DataBinding(Object sender, EventArgs e)
    {
      // Use the sender parameter to retrieve the Label control
      // being bound to data.
      Label titleLabelControl = (Label)sender;

      // Retrieve the value to bind to the Label control. First,
      // use the NamingContainer property to retrieve the parent 
      // control of the Label control. In this example, the parent 
      // control is the FormView control.
      FormView formViewContainer = (FormView)titleLabelControl.NamingContainer;

      // Get the data item bound to the FormView control.
      DataRowView rowView = (DataRowView)formViewContainer.DataItem;

      // Use the data item to retrieve the value of the LastName field
      // Set the Text property of the Label control to this value.         
      titleLabelControl.Text = rowView["Title"].ToString();
    }

  }

  void Page_Load(Object sender, EventArgs e)
  {

    // Create a new FormView object.
    FormView employeesFormView = new FormView();

    // Set the FormView object's properties.
    employeesFormView.ID = "EmployeesFormView";
    employeesFormView.DataSourceID = "EmployeeSource";
    employeesFormView.AllowPaging = true;
    employeesFormView.HeaderText = "Employee Name";
    employeesFormView.DataKeyNames = new String[1] { "EmployeeID" };

    // Programmatically register the event handler for the 
    // ItemDeleting event of the FormView control.
    employeesFormView.ItemDeleting += new FormViewDeleteEventHandler(EmployeeFormView_ItemDeleting);

    // Create the dynamic template using the custom template class.
    employeesFormView.ItemTemplate = new EmployeeTemplate();

    // Add the FormView object to the Controls collection
    // of the PlaceHolder control.
    FormViewPlaceHolder.Controls.Add(employeesFormView);

  }

  void EmployeeFormView_ItemDeleting(Object sender, FormViewDeleteEventArgs e)
  {

    // Use the sender parameter to retrieve the FormView
    // control that raised the event.
    FormView employeeFormView = (FormView)sender;

    // Retrieve the TitleLabel Label control from the
    // data row.
    FormViewRow row = employeeFormView.Row;
    Label titleLabel = (Label)row.FindControl("TitleLabel");

    // Cancel the delete operation if the user attempts to 
    // delete a protected record. In this example, records for
    // employees with a "Sales Manager" job title are protected.
    if (titleLabel.Text.Equals("Sales Manager"))
    {
      e.Cancel = true;
      MessageLabel.Text = "You cannot delete this record.";
    }

  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>FormViewDeleteEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">

      <h3>FormViewDeleteEventHandler Example</h3>

      <!-- Use a PlaceHolder control as the container for the -->
      <!-- dynamically generated FormView control.            -->       
      <asp:placeholder id="FormViewPlaceHolder"
        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="EmployeeSource"
        selectcommand="Select [EmployeeID], [LastName], [FirstName], [Title], [PhotoPath] From [Employees]"
        deletecommand="Delete [Employees] Where [EmployeeID]=@EmployeeID"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>

    </form>
  </body>
</html>

Im folgenden Beispiel wird veranschaulicht, wie deklarativ hinzufügen einer FormViewDeleteEventHandler Delegat, der die ItemDeleting -Ereignis ein FormView Steuerelement.


<%@ 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 EmployeeFormView_ItemDeleting(Object sender, FormViewDeleteEventArgs e)
  {
    // Get the employee ID, name, and job title from the Keys and Values
    // properties.
    String keyValue = e.Keys["EmployeeID"].ToString();
    String employeeName = e.Values["FirstName"].ToString() +
      " " + e.Values["LastName"].ToString();
    String title = e.Values["Title"].ToString();

    // Cancel the delete operation if the user attempts to 
    // delete a protected record. In this example, records for
    // employees with a "Sales Manager" job title are protected.
    if (title.Equals("Sales Manager"))
    {
      e.Cancel = true;
      MessageLabel.Text = "You cannot delete record " +
        e.RowIndex.ToString() + ". " + employeeName +
        " (Employee Number " + keyValue.ToString() +
        ") is protected.";
    }

  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>FormViewDeleteEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">

      <h3>FormViewDeleteEventHandler Example</h3>

      <asp:formview id="EmployeeFormView"
        datasourceid="EmployeeSource"
        allowpaging="true"
        datakeynames="EmployeeID"
        onitemdeleting="EmployeeFormView_ItemDeleting"  
        runat="server">

        <itemtemplate>

          <table>
            <tr>
              <td>
                <asp:image id="EmployeeImage"
                  imageurl='<%# Eval("PhotoPath") %>'
                  alternatetext='<%# Eval("LastName") %>' 
                  runat="server"/>
              </td>
              <td>
                <asp:label id="FirstNameLabel"
                  text='<%#Bind("FirstName")%>'
                  font-bold="true"
                  runat="server"/>
                <asp:label id="LastNameLabel"
                  text='<%#Bind("LastName")%>'
                  font-bold="true"
                  runat="server"/>
                <br/>     
                <asp:label id="TitleLabel"
                  text='<%#Bind("Title")%>'
                  runat="server"/>        
              </td>
            </tr>
            <tr>
              <td colspan="2">
                <asp:button id="DeleteButton"
                  text="Delete Record"
                  commandname="Delete"
                  runat="server" />
              </td>
            </tr>
          </table>

        </itemtemplate>         

      </asp:formview>

      <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="EmployeeSource"
        selectcommand="Select [EmployeeID], [LastName], [FirstName], [Title], [PhotoPath] From [Employees]"
        deletecommand="Delete [Employees] Where [EmployeeID]=@EmployeeID"
        connectionstring="<%$ ConnectionStrings:NorthWindConnectionString%>" 
        runat="server"/>

    </form>
  </body>
</html>

.NET Framework
Verfügbar seit 2.0
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