GridViewPageEventHandler Delegate

 

Represents the method that handles the PageIndexChanging event of a GridView control.

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

Public Delegate Sub GridViewPageEventHandler (
	sender As Object,
	e As GridViewPageEventArgs
)

Parameters

sender
Type: System.Object

The source of the event.

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

A GridViewPageEventArgs object that contains the event data.

The GridView control raises the PageIndexChanging event when a pager button (a button with its CommandName property set to "Page") within the control is clicked, but before the GridView control handles the paging operation. This allows you to provide an event-handling method that performs a custom routine, such as canceling the paging operation, whenever this event occurs.

System_CAPS_noteNote

Pager buttons are usually located in the pager row of a GridView control.

When you create a GridViewPageEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see NIB: Events and Delegates.

The following example demonstrates how to programmatically add a GridViewPageEventHandler delegate to the PageIndexChanging event of a GridView control.


<%@ 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 Page_Load(ByVal sender As Object, ByVal e As EventArgs)

    ' Create a new GridView control.
    Dim customersGridView As New GridView()

    ' Set the GridView object's properties.
    customersGridView.ID = "CustomersGridView"
    customersGridView.DataSourceID = "CustomersSource"
    customersGridView.AutoGenerateColumns = True
    customersGridView.EmptyDataText = "No data available."
    customersGridView.AllowPaging = True
    customersGridView.AutoGenerateEditButton = True
    customersGridView.PagerSettings.Mode = PagerButtons.Numeric
    customersGridView.PagerSettings.Position = PagerPosition.Bottom
    customersGridView.PagerSettings.PageButtonCount = 10
    customersGridView.PagerStyle.BackColor = System.Drawing.Color.LightBlue
    Dim keyArray() As String = {"CustomerID"}
    customersGridView.DataKeyNames = keyArray

    ' Programmatically register the event-handling methods.
    AddHandler customersGridView.PageIndexChanging, AddressOf CustomersGridView_PageIndexChanging
    AddHandler customersGridView.RowCancelingEdit, AddressOf CustomersGridView_RowCancelingEdit

    ' Add the GridView control to the Controls collection
    ' of the PlaceHolder control.
    GridViewPlaceHolder.Controls.Add(customersGridView)

  End Sub

  Sub CustomersGridView_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)

    ' User the sender parameter to retrieve the GridView control
    ' that raised the event.
    Dim customersGridView As GridView = CType(sender, GridView)

    ' Cancel the paging operation if the user attempts to navigate
    ' to another page while the GridView control is in edit mode. 
    If customersGridView.EditIndex <> -1 Then

      ' Use the cancel property to cancel the paging operation.
      e.Cancel = True

      ' Display an error message.
      Dim newPageNumber As Integer = e.NewPageIndex + 1
      Message.Text = "Please update the record before moving to page " & _
        newPageNumber.ToString() & "."

    Else

      ' Clear the error message.
      Message.Text = ""

    End If

  End Sub

  Sub CustomersGridView_RowCancelingEdit(ByVal sender As Object, ByVal e As GridViewCancelEditEventArgs)

    ' Clear the error message.
    Message.Text = ""

  End Sub

</script>

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

      <h3>GridViewPageEventHandler Example</h3>

      <asp:label id="Message"
        forecolor="Red"
        runat="server"/>

      <br/>  

      <asp:placeholder id="GridViewPlaceHolder"
        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="CustomersSource"
        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>

The following example demonstrates how to declaratively add a GridViewPageEventHandler delegate to the PageIndexChanging event of a GridView control.


<%@ 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 CustomersGridView_PageIndexChanging(ByVal sender As Object, ByVal e As GridViewPageEventArgs)

    ' Cancel the paging operation if the user attempts to navigate
    ' to another page while the GridView control is in edit mode. 
    If CustomersGridView.EditIndex <> -1 Then

      ' Use the Cancel property to cancel the paging operation.
      e.Cancel = True

      ' Display an error message.
      Dim newPageNumber As Integer = e.NewPageIndex + 1
      Message.Text = "Please update the record before moving to page " & _
        newPageNumber.ToString() & "."

    Else

      ' Clear the error message.
      Message.Text = ""

    End If

  End Sub

  Sub CustomersGridView_RowCancelingEdit(ByVal sender As Object, ByVal e As GridViewCancelEditEventArgs)

    ' Clear the error message.
    Message.Text = ""

  End Sub

</script>

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

      <h3>GridView PageIndexChanging Example</h3>

      <asp:label id="Message"
        forecolor="Red"
        runat="server"/>

      <br/>  

      <asp:gridview id="CustomersGridView" 
        datasourceid="CustomersSource" 
        autogeneratecolumns="true"
        emptydatatext="No data available." 
        allowpaging="true"
        autogenerateeditbutton="true"
        datakeynames="CustomerID"  
        onpageindexchanging="CustomersGridView_PageIndexChanging"
        onrowcancelingedit="CustomersGridView_RowCancelingEdit" 
        runat="server">

        <pagersettings mode="Numeric"
          position="Bottom"           
          pagebuttoncount="10"/>

        <pagerstyle backcolor="LightBlue"/>

      </asp:gridview>

      <!-- 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="CustomersSource"
        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>

.NET Framework
Available since 2.0
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