This example demonstrates on how are we going to limit the number of characters to be typed into the TextBox using JavaScript and display the remaining characters in a Label Control.
<script type="text/javascript" language="javascript">
function validatelimit(obj, maxchar)
{
if(this.id) obj = this;
var remaningChar = maxchar - obj.value.length;
document.getElementById('<%= Label1.ClientID %>').innerHTML = remaningChar;
if( remaningChar <= 0)
{
obj.value = obj.value.substring(maxchar,0);
alert('Character Limit exceeds!');
return false;
}
else
{return true;}
}
</script>
<body runat="server">
<form id="form1" runat="server">
<asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" onkeyup="validatelimit(this,300)"> </asp:TextBox>
<asp:Label ID="Label1" runat="server" Text="0"></asp:Label>
</form>
</body>
Note: 300 is the MAX length of the characters in the TextBox..Just change the value of 300 based on your requirements..