ClientScriptManager.GetPostBackEventReference Method (Control, String)

 

Returns a string that can be used in a client event to cause postback to the server. The reference string is defined by the specified control that handles the postback and a string argument of additional event information.

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

public string GetPostBackEventReference(
	Control control,
	string argument
)

Parameters

control
Type: System.Web.UI.Control

The server Control that processes the postback on the server.

argument
Type: System.String

A string of optional arguments to pass to the control that processes the postback.

Return Value

Type: System.String

A string that, when treated as script on the client, initiates the postback.

Exception Condition
ArgumentNullException

The specified Control is null.

To implement the IPostBackEventHandler interface for a Page, use the directive.

The GetPostBackEventReference method can be used with the Button control when the UseSubmitBehavior property is false. In this scenario, the GetPostBackEventReference method returns the client postback event for the Button control.

The following code example demonstrates the use of the GetPostBackEventReference method. The custom control, MyControl, implements the IPostBackEventHandler interface. When the button on the page is clicked, the RaisePostBackEvent method of the custom control is invoked.

<%@ 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">

  public class MyControl : Label, IPostBackEventHandler
  {

    // Use the constructor to defined default label text.
    public MyControl()
    {
      base.Text = "No postback raised.";
    }

    // Implement the RaisePostBackEvent method from the
    // IPostBackEventHandler interface. 
    public void RaisePostBackEvent(string eventArgument)
    {
      base.Text = "Postback handled by " + this.ID.ToString() + ". <br/>" +
                  "Postback caused by " + eventArgument.ToString() + ".";

    }
  }

  protected void Page_Load(object sender, EventArgs e)
  {
    // Get a ClientScriptManager reference from the Page class.
    ClientScriptManager cs = Page.ClientScript;

    // Create an instance of the custom label control and 
    // add it to the page.
    MyControl mycontrol = new MyControl();
    mycontrol.ID = "mycontrol1";
    PlaceHolder1.Controls.Add(mycontrol);
    PlaceHolder1.Controls.Add(new LiteralControl("<br/>"));

    // Create a button element with its onClick attribute defined
    // to create a postback event reference to the custom label control.
    HtmlInputButton b = new HtmlInputButton();
    b.ID = "mybutton1";
    b.Value = "Click";
    b.Attributes.Add("onclick", cs.GetPostBackEventReference(mycontrol, b.ID.ToString()));
    PlaceHolder1.Controls.Add(b);
    PlaceHolder1.Controls.Add(new LiteralControl("<br/>"));

    // Create a link element with its href attribute defined
    // to create a postback event reference to the custom label control.
    HtmlAnchor a = new HtmlAnchor();
    a.ID = "myanchor1";
    a.InnerText = "link";
    a.HRef = cs.GetPostBackClientHyperlink(mycontrol, a.ID.ToString());
    PlaceHolder1.Controls.Add(a);
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>ClientScriptManager Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <asp:PlaceHolder id="PlaceHolder1" 
                       runat="server">
      </asp:PlaceHolder>
    </div>
    </form>
</body>
</html>

The following code example has the same functionality as the preceding one, except that instead of a custom control, the Page class implements the IPostBackEventHandler interface.

<%@ Page Language="C#"  %>
<%@ Implements Interface="System.Web.UI.IPostBackEventHandler" %>

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

<script runat="server">

  public void RaisePostBackEvent(string eventArgument)
  {
    Label1.Text = "Postback handled by " + this.ID.ToString() + ". <br/>" +
                  "Postback caused by " + eventArgument.ToString() + "."; ;
  }

  protected void Page_Load(object sender, EventArgs e)
  {
    // Get a ClientScriptManager reference from the Page class.
    ClientScriptManager cs = Page.ClientScript;

    // Create a button element with its onClick attribute defined
    // to create a postback event reference to the custom label control.
    HtmlInputButton b = new HtmlInputButton();
    b.ID = "mybutton1";
    b.Value = "Click";
    b.Attributes.Add("onclick", cs.GetPostBackEventReference(this, b.ID.ToString()));
    PlaceHolder1.Controls.Add(b);
    PlaceHolder1.Controls.Add(new LiteralControl("<br/>"));

    // Create a link element with its href attribute defined
    // to create a postback event reference to the custom label control.
    HtmlAnchor a = new HtmlAnchor();
    a.ID = "myanchor1";
    a.InnerText = "link";
    a.HRef = cs.GetPostBackClientHyperlink(this, a.ID.ToString());
    PlaceHolder1.Controls.Add(a);
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>ClientScriptManager Example</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
      <asp:Label id="Label1"
                 runat="server" />
      <br />
      <asp:PlaceHolder id="PlaceHolder1" 
                       runat="server">
      </asp:PlaceHolder>
    </div>
    </form>
</body>
</html>

.NET Framework
Available since 2.0
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