In this article I will explain how to implement Character Count and Maximum Character Length Validation for ASP.Net MultiLine TextBox in general HTML terms the TextArea control.
HTML TextArea control does not have MaxLength property like the normal TextBox and Password fields have. Hence I have built a MaxLength jQuery plugin which simulates the working of the normal MaxLength with the help of JavaScript and jQuery.
Implementing the jQuery MaxLength Plugin for ASP.Net MultiLine TextBox (TextArea)
Below you will notice the implementation of the jQuery MaxLength plugin. The jQuery MaxLength plugin has the following required and optional parameters
1. MaxLength (required) – Integer value indicating the Maximum character length limit.
2. CharacterCountControl (optional) – By default the plugin will display character count below the TextArea, but user has option to explicitly specify the Character Count Control.
Note: The character count control can only HTML SPAN or DIV.
3. DisplayCharacterCount (optional) – Default true. If set to false the Character counting will be disabled.
<html xmlns="">
<head runat="server">
    <script type="text/javascript" src="">script>
    <script type="text/javascript" src="MaxLength.min.js">script>
    <script type="text/javascript">
        $(function () {
            //Normal Configuration
            $("[id*=TextBox1]").MaxLength({ MaxLength: 10 });
            //Specifying the Character Count control explicitly
                MaxLength: 15,
                CharacterCountControl: $('#counter')
            //Disable Character Count
                MaxLength: 20,
                DisplayCharacterCount: false
    <form id="form1" runat="server">
    <div id="counter">
    <asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" Width="300" Height="100"
        Text="Mudassar Khan">asp:TextBox>
    <br />
    <br />
    <asp:TextBox ID="TextBox2" runat="server" TextMode="MultiLine" Width="300" Height="100">asp:TextBox>
    <br />
    <br />
    <asp:TextBox ID="TextBox3" runat="server" TextMode="MultiLine" Width="300" Height="100">asp:TextBox>

The above code has been tested in the following browsers

Internet Explorer  FireFox  Chrome  Safari  Opera 

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