Asp.net Custom Validator control

The CustomValidator control is used to validate an input control with a user defined task, either from server side or client side. Normally this control is used when you feel that there is no other validation control fit in your requirement.

Following are main properties of the validation control.

ClientValidationFunction	Gets or sets the validation function that will be used in client side (JavaScript function).
OnServerValidate	Method that fires after post back.
ControlToCompare	Gets or sets the ID of the control whose value will be compared with the currently entered value.
Operator	DataTypeCheck/Equal/GreaterThan/GreaterThanEqual/LessThan/LessThanEqual/NotEqual. Used to specify the comparison operation to peform. In case of DataTypeCheck, ControlToCompare properties are ingnored.
Display	Dynamic/Static. Used to indicate how the area of error message will be allocated. Dynamic: Error message area will only be allocated when error will be displayed. Static: Error messagea area will be allocated in either case.
Enabled	true/false. Gets or sets whether to enable the validation control or not.
ErrorMessage	Gets or sets the text of the error message that will be displayed when validation fails (This is displayed when ValidationSummary validatoin control is used.).
Text	Gets or sets the description of the error message text.
ValidationGroup	Gets or sets the validation group it belongs to. This is used to group a set of controls.
SetFocusOnError	true/false. Used to move focus on the control that fails the validation.

Example - 

// Form & Validation Control /////////////////////////
<asp:Label ID="lbl" AssociatedControlID="TextBox1" runat="Server" Text="Write into TextBox"></asp:Label>
    <asp:TextBox ID="TextBox1" runat="Server"></asp:TextBox>
    <asp:RequiredFieldValidator ID="req1" runat="Server" ControlToValidate="TextBox1" ErrorMessage="1st TextBox is Mandatory field" Text="<br>Please write something in 1st  Box."></asp:RequiredFieldValidator>
    <asp:CustomValidator ID="CustomValidator1" runat="Server" ControlToValidate="TextBox1" ClientValidationFunction="CheckForHardCodedValue" ErrorMessage="Value doens't match." Text="TextBox value must be [GOLD]" OnServerValidate="ValidateServerSide"></asp:CustomValidator>
    <asp:Button ID="btnSubmit" runat="Server" OnClick="WriteTextBoxValue" Text="Submit" />               
    <asp:ValidationSummary ID="ValidationSummary" runat="Server" ShowMessageBox="true" />

// JavaScript validation function /////////////////////////
function CheckForHardCodedValue(source, arguments)
    {
        var tID = '<%= TextBox1.ClientID %>';
        if (document.getElementById(tID).value == 'GOLD')
            arguments.IsValid = true;
        else
            arguments.IsValid = false;
    }

// Server side function to validate /////////////////////////
 protected void ValidateServerSide(object source, ServerValidateEventArgs args)
    {
        if (args.Value.Equals("GOLD"))
        {
            args.IsValid = true;
            lblMessage.Text += "Page is valid.<br />";
        }
        else
        {
            args.IsValid = false;
            lblMessage.Text += "Page is NOT valid.<br />";
        }
    }       
       

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