Auto Resize text Box
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<style type="text/css">
.clsTxt {
width: 200px;
min-height: 25px;
max-height: 200px;
resize: none;
}
</style>
<script>
function resizeTextBox(txt) {
txt.style.height = "1px";
txt.style.height = (1 + txt.scrollHeight) + "px";
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<table>
<tr>
<td>Description: </td>
<td>
<asp:TextBox ID="txtDescription" CssClass="clsTxt" runat="server"onkeyup="resizeTextBox(this)" TextMode="MultiLine"></asp:TextBox>
<%--<textarea class="clsTxt"
onkeyup="resizeTextBox(this)"></textarea>--%>
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
Note: In this article I have demonstrated the concept using
asp.net multiline textbox. But if you want to implement it on HTML textarea then use
<textarea class="clsTxt" onkeyup="resizeTextBox(this)"></textarea>
Instead of
<asp:TextBox ID="txtDescription" CssClass="clsTxt" runat="server" onkeyup="resizeTextBox(this)"TextMode="MultiLine"></asp:TextBox>