FormViewDeletedEventHandler Делегат

Определение

Представляет метод, обрабатывающий событие ItemDeleted элемента управления FormView.

public delegate void FormViewDeletedEventHandler(System::Object ^ sender, FormViewDeletedEventArgs ^ e);
public delegate void FormViewDeletedEventHandler(object sender, FormViewDeletedEventArgs e);
type FormViewDeletedEventHandler = delegate of obj * FormViewDeletedEventArgs -> unit
Public Delegate Sub FormViewDeletedEventHandler(sender As Object, e As FormViewDeletedEventArgs)

Параметры

sender
Object

Источник события.

e
FormViewDeletedEventArgs

Объект FormViewDeletedEventArgs, содержащий данные события.

Примеры

В следующем примере показано, как программным способом FormViewDeletedEventHandler добавить делегат в ItemDeleted событие FormView элемента управления .


<%@ 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
    // the 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 and LastName field from the data source.
      // To support data-binding, create event handlers 
      // for the DataBinding event of the child child controls.
      // The event handlers must bind the appropriate value 
      // to the control.
      Label firstNameLabel = new Label();
      firstNameLabel.ID = "FirstNameLabel";
      firstNameLabel.DataBinding += new EventHandler(FirstNameLabel_DataBinding);

      LiteralControl nameLineBreak = new LiteralControl("<br/>");
      LiteralControl buttonLineBreak = new LiteralControl("<br/>");

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

      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(nameLineBreak);
      container.Controls.Add(lastNameLabel);
      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();
    }

  }

  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 
    // ItemDeleted event of the FormView control.
    employeesFormView.ItemDeleted += new FormViewDeletedEventHandler(EmployeeFormView_ItemDeleted);

    // 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_ItemDeleted(Object sender, FormViewDeletedEventArgs e)
  {
    // Use the Exception property to determine whether an exception
    // occurred during the delete operation.
    if (e.Exception == null)
    {
      // Use the AffectedRows property to determine whether the
      // record was deleted. Sometimes an error might occur that 
      // does not raise an exception, but prevents the delete
      // operation from completing.
      if (e.AffectedRows == 1)
      {
        MessageLabel.Text = "Record deleted successfully.";
      }
      else
      {
        MessageLabel.Text = "An error occurred during the delete operation.";
      }
    }
    else
    {
      // Insert the code to handle the exception.
      MessageLabel.Text = e.Exception.Message;
      
      // Use the ExceptionHandled property to indicate that the 
      // exception is already handled.
      e.ExceptionHandled = true;
    }
  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>FormViewDeletedEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>FormViewDeletedEventHandler 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>

<%@ page language="VB" %>
<%@ 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 NotInheritable Class EmployeeTemplate
    Implements ITemplate
    
    ' When implementing the ITemplate interface, you must
    ' the implement the InstantiateIn method. The FormView
    ' control calls this method to create the template's 
    ' content. 
    Sub InstantiateIn(ByVal container As Control) Implements ITemplate.InstantiateIn
    
      ' Create the child controls contained in the template.
      ' For this example, the item template displays the
      ' FirstName and LastName field from the data source.
      ' To support data-binding, create event handlers 
      ' for the DataBinding event of the child child controls.
      ' The event handlers must bind the appropriate value 
      ' to the control.
      Dim firstNameLabel As New Label()
      firstNameLabel.ID = "FirstNameLabel"
      AddHandler firstNameLabel.DataBinding, AddressOf FirstNameLabel_DataBinding
      
      Dim nameLineBreak As New LiteralControl("<br/>")
      Dim buttonLineBreak As New LiteralControl("<br/>")

      Dim lastNameLabel As New Label()
      lastNameLabel.ID = "LastNameLabel"
      AddHandler lastNameLabel.DataBinding, AddressOf LastNameLabel_DataBinding

      ' Create a custom button control to display in the item
      ' template. When a button within a FormView control is 
      ' clicked, the ItemCommand event is raised. The ItemCommand
      ' event is used to handle the clicking of this button.
      Dim deleteButton As 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(nameLineBreak)
      container.Controls.Add(lastNameLabel)
      container.Controls.Add(buttonLineBreak)
      container.Controls.Add(deleteButton)

    End Sub
    
    ' This event handler binds the value of the FirstName field
    ' to the FirstNameLabel Label control displayed in the template.
    Private Sub FirstNameLabel_DataBinding(ByVal sender As Object, ByVal e As EventArgs)

      ' Use the sender parameter to retrieve the Label control
      ' being bound to data.
      Dim firstNameLabelControl As Label = CType(sender, Label)

      ' 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.
      Dim formViewContainer As FormView = CType(firstNameLabelControl.NamingContainer, FormView)
      
      ' Get the data item bound to the FormView control.
      Dim rowView As DataRowView = CType(formViewContainer.DataItem, DataRowView)

      ' 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()
  
    End Sub

    ' This event handler binds the value of the LastName field
    ' to the LastNameLabel Label control displayed in the template.
    Private Sub LastNameLabel_DataBinding(ByVal sender As Object, ByVal e As EventArgs)

      ' Use the sender parameter to retrieve the Label control
      ' being bound to data.
      Dim lastNameLabelControl As Label = CType(sender, Label)

      ' 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.
      Dim formViewContainer As FormView = CType(lastNameLabelControl.NamingContainer, FormView)

      ' Get the data item bound to the FormView control.
      Dim rowView As DataRowView = CType(formViewContainer.DataItem, DataRowView)

      ' 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()
    
    End Sub

  End Class

  Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    ' Create a new FormView object.
    Dim employeesFormView As New FormView()

    ' Set the FormView object's properties.
    employeesFormView.ID = "EmployeesFormView"
    employeesFormView.DataSourceID = "EmployeeSource"
    employeesFormView.AllowPaging = True
    employeesFormView.HeaderText = "Employee Name"
    
    Dim keyArray() As String = {"EmployeeID"}
    employeesFormView.DataKeyNames = keyArray

    ' Programmatically register the event handler for the 
    ' ItemDeleted event of the FormView control.
    AddHandler employeesFormView.ItemDeleted, AddressOf EmployeeFormView_ItemDeleted

    ' 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)

  End Sub

  Sub EmployeeFormView_ItemDeleted(ByVal sender As Object, ByVal e As FormViewDeletedEventArgs)
  
    ' Use the Exception property to determine whether an exception
    ' occurred during the delete operation.
    If e.Exception Is Nothing Then
    
      ' Use the AffectedRows property to determine whether the
      ' record was deleted. Sometimes an error might occur that 
      ' does not raise an exception, but prevents the delete
      ' operation from completing.
      If e.AffectedRows = 1 Then
      
        MessageLabel.Text = "Record deleted successfully."
      
      Else
              
        MessageLabel.Text = "An error occurred during the delete operation."
      
      End If
    
    Else
    
      ' Insert the code to handle the exception.
      MessageLabel.Text = e.Exception.Message
      
      ' Use the ExceptionHandled property to indicate that the 
      ' exception is already handled.
      e.ExceptionHandled = True
      
    End If
    
  End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>FormViewDeletedEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>FormViewDeletedEventHandler 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>

В следующем примере показано, как декларативно добавить FormViewDeletedEventHandler делегат в ItemDeleted событие FormView элемента управления .


<%@ 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_ItemDeleted(Object sender, FormViewDeletedEventArgs e)
  {
    // Use the Exception property to determine whether an exception
    // occurred during the delete operation.
    if (e.Exception == null)
    {
      // Use the AffectedRows property to determine whether the
      // record was deleted. Sometimes an error might occur that 
      // does not raise an exception, but prevents the delete
      // operation from completing.
      if (e.AffectedRows == 1)
      {
        MessageLabel.Text = "Record deleted successfully.";
      }
      else
      {
        MessageLabel.Text = "An error occurred during the delete operation.";
      }
    }
    else
    {
      // Insert the code to handle the exception.
      MessageLabel.Text = e.Exception.Message;
      
      // Use the ExceptionHandled property to indicate that the 
      // exception has already been handled.
      e.ExceptionHandled = true;
    }
  }

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>FormViewDeletedEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>FormViewDeletedEventHandler Example</h3>
                       
      <asp:formview id="EmployeeFormView"
        datasourceid="EmployeeSource"
        allowpaging="true"
        datakeynames="EmployeeID"
        onitemdeleted="EmployeeFormView_ItemDeleted"  
        runat="server">
        
        <itemtemplate>
        
          <table>
            <tr>
              <td>
                <asp:image id="EmployeeImage"
                  imageurl='<%# Eval("PhotoPath") %>'
                  alternatetext='<%# Eval("LastName") %>' 
                  runat="server"/>
              </td>
              <td>
                <h3><%# Eval("FirstName") %> <%# Eval("LastName") %></h3>      
                <%# Eval("Title") %>        
              </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>

<%@ Page language="VB" %>

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

  Sub EmployeeFormView_ItemDeleted(ByVal sender As Object, ByVal e As FormViewDeletedEventArgs) Handles EmployeeFormView.ItemDeleted
  
    ' Use the Exception property to determine whether an exception
    ' occurred during the delete operation.
    If e.Exception Is Nothing Then
    
      ' Use the AffectedRows property to determine whether the
      ' record was deleted. Sometimes an error might occur that 
      ' does not raise an exception, but prevents the delete
      ' operation from completing.
      If e.AffectedRows = 1 Then
      
        MessageLabel.Text = "Record deleted successfully."
      
      Else
              
        MessageLabel.Text = "An error occurred during the delete operation."
      
      End If
    
    Else
    
      ' Insert the code to handle the exception.
      MessageLabel.Text = e.Exception.Message
      
      ' Use the ExceptionHandled property to indicate that the 
      ' exception has already been handled.
      e.ExceptionHandled = True
      
    End If
    
  End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>FormViewDeletedEventHandler Example</title>
</head>
<body>
    <form id="form1" runat="server">
        
      <h3>FormViewDeletedEventHandler Example</h3>
                       
      <asp:formview id="EmployeeFormView"
        datasourceid="EmployeeSource"
        allowpaging="true"
        datakeynames="EmployeeID" 
        runat="server">
        
        <itemtemplate>
        
          <table>
            <tr>
              <td>
                <asp:image id="EmployeeImage"
                  imageurl='<%# Eval("PhotoPath") %>'
                  alternatetext='<%# Eval("LastName") %>' 
                  runat="server"/>
              </td>
              <td>
                <h3><%# Eval("FirstName") %> <%# Eval("LastName") %></h3>      
                <%# Eval("Title") %>        
              </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>

Комментарии

Элемент FormView управления вызывает ItemDeleted событие при нажатии кнопки Удалить (кнопка со свойством CommandName "Удалить") в элементе управления, но после FormView того, как элемент управления удаляет запись. Это позволяет предоставить метод обработки событий, который выполняет настраиваемую подпрограмму, например проверку результатов операции удаления при каждом возникновении этого события.

При создании делегата FormViewDeletedEventHandler необходимо указать метод, обрабатывающий событие. Чтобы связать событие с обработчиком событий, нужно добавить в событие экземпляр делегата. Обработчик событий вызывается всякий раз, когда происходит событие, если делегат не удален. Дополнительные сведения о делегатах обработчика событий см. в разделе Обработка и вызов событий.

Методы расширения

GetMethodInfo(Delegate)

Получает объект, представляющий метод, представленный указанным делегатом.

Применяется к

См. также раздел