custom validator

// type this part between form tag

Custom text:<br />
<asp:TextBox runat="server" id="txtCustom" />
<asp:CustomValidator runat="server" id="cusCustom" controltovalidate="txtCustom" onservervalidate="cusCustom_ServerValidate" errormessage="The text must be exactly 8 characters long!" />
<br /><br />
// type this part in code behind

protected void cusCustom_ServerValidate(object sender, ServerValidateEventArgs e)
{
    if(e.Value.Length == 8)
        e.IsValid = true;
    else
        e.IsValid = false;
}

regular expression validator

// type this part between form tag

4 digit number:<br />
<asp:TextBox runat="server" id="txtNumber" />
<asp:RegularExpressionValidator runat="server" id="rexNumber" controltovalidate="txtNumber" validationexpression="^[0-9]{4}$" errormessage="Please enter a 4 digit number!" />
<br /><br />

range validator

// type this part between form tag

Date:<br />
<asp:TextBox runat="server" id="txtDate" />
<asp:RangeValidator runat="server" id="rngDate" controltovalidate="txtDate" type="Date" minimumvalue="01-01-2006" maximumvalue="31-12-2006" errormessage="Please enter a valid date within 2006!" />
<br /><br />

compare validator

// type this part in between form tag

Small number:<br />
<asp:TextBox runat="server" id="txtSmallNumber" /><br /><br />
Big number:<br />
<asp:TextBox runat="server" id="txtBigNumber" /><br />
<asp:CompareValidator runat="server" id="cmpNumbers" controltovalidate="txtSmallNumber" controltocompare ="txtBigNumber" operator="LessThan" type="Integer" errormessage="The first number should be smaller than the second number!" /><br />

RequiredFieldValidator

//type this part in between form tag

<form id="form1" runat="server">
    Your name:<br />
    <asp:TextBox runat="server" id="txtName" />
    <asp:RequiredFieldValidator runat="server" id="reqName" controltovalidate="txtName" errormessage="Please enter your name!" />
    <br /><br />
    <asp:Button runat="server" id="btnSubmitForm" text="Ok" onclick="btnSubmitForm_Click" /></form>
//type this part in code behind

protected void btnSubmitForm_Click(object sender, EventArgs e)
{
    if(Page.IsValid)
    {
        btnSubmitForm.Text = "My form is valid!";
    }
}