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ClientScriptManager.RegisterForEventValidation Method (String, String)

Registers an event reference for validation with a unique control ID and event arguments representing the client control generating the event.

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

public void RegisterForEventValidation(
	string uniqueId,
	string argument
)

Parameters

uniqueId
Type: System.String

A unique ID representing the client control generating the event.

argument
Type: System.String

Event arguments passed with the client event.

ExceptionCondition
InvalidOperationException

The method is called prior to the Render method.

The following code example demonstrates using the RegisterForEventValidation method and the ValidateEvent method to register a callback for validation and to validate that the callback originated from the page. To improve on the validation shown in the example, you could modify the validation argument parameter to contain information specific to the user such as an identity or role

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

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

<script runat="server" >

    string _cbMessage = "";
    // Define method that processes the callbacks on server.
    public void RaiseCallbackEvent(String eventArgument)
    {
        try
        {
            Page.ClientScript.ValidateEvent(button1.UniqueID, this.ToString());
            _cbMessage = "Correct event raised callback.";
        }
        catch (Exception ex)
        {
            _cbMessage = "Incorrect event raised callback.";
        }
    }

    // Define method that returns callback result.
    public string GetCallbackResult()
    {
        return _cbMessage;
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            ClientScriptManager cs = Page.ClientScript;
            String cbReference = cs.GetCallbackEventReference("'" +
                Page.UniqueID + "'", "arg", "ReceiveServerData", "",
                "ProcessCallBackError", false);
            String callbackScript = "function CallTheServer(arg, context) {" +
                cbReference + "; }";
            cs.RegisterClientScriptBlock(this.GetType(), "CallTheServer",
                callbackScript, true);
        }
    }
    protected override void Render(HtmlTextWriter writer)
    {
        Page.ClientScript.RegisterForEventValidation(button1.UniqueID, this.ToString());
        base.Render(writer);
    }

</script>

<script type="text/javascript">
var value1 = new Date();
function ReceiveServerData(arg, context)
{
    Message.innerText = arg;
    Label1.innerText = "Callback completed at " + value1;
    value1 = new Date();
}
function ProcessCallBackError(arg, context)
{
    Message.innerText = 'An error has occurred.';
}
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>CallBack Event Validation Example</title>
</head>
<body>
    <form id="Form1" runat="server">
    <div>
      Callback result: <span id="Message"></span>
      <br /> <br />
      <input type="button"
             id="button1" 
             runat="server"
             value="ClientCallBack" 
             onclick="CallTheServer(value1, null )"/>
      <br /> <br />
      <asp:Label id="Label1" runat="server"/>
    </div>
    </form>
</body>
</html>

The following code example demonstrates using the RegisterForEventValidation method to register a callback for validation.

<%@ Page EnableEventValidation="true" Language="C#"  %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Register an option for event validation</title>
    <script runat="server">
        protected override void Render(HtmlTextWriter writer)
        {
            ClientScript.RegisterForEventValidation("DropDownList1", "This is Option 1");
            ClientScript.RegisterForEventValidation("DropDownList1", "This is Option 2");
            ClientScript.RegisterForEventValidation("DropDownList1", "This is Option 3");
            // Uncomment the line below when you want to specifically register the option for event validation.
            // ClientScript.RegisterForEventValidation("DropDownList1", "Is this option registered for event validation?");
            base.Render(writer);
        }
    </script>
    <script type="text/javascript">
        function Initialize()
        {
            var oOption = document.createElement("OPTION");
            document.all("DropDownList1").options.add(oOption);
            oOption.innerText = "This is Option 1";            
            oOption = document.createElement("OPTION");            
            document.all("DropDownList1").options.add(oOption);
            oOption.innerText = "This is Option 2";
            oOption = document.createElement("OPTION");                
            document.all("DropDownList1").options.add(oOption); 
            oOption.innerText = "This is Option 3";
            oOption = document.createElement("OPTION");                
            document.all("DropDownList1").options.add(oOption); 
            oOption.innerText = "Is this option registered for event validation?";
        }
    </script>
</head>
<body onload="Initialize();">
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="DropDownList1" runat="server"></asp:DropDownList>
        <asp:Button ID="Button1" runat="server" Text="Postback to server for validation" />
    </div>
    </form>
</body>
</html>

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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