Validate file Extension in ASP.net using JavaScript
I had seen many post in forums people asking how to
make sure only image files or only .doc file or .xls file
should be uploaded or selected.
Below is a simple
JavaScript function which make sure that only the extension
specified is valid during upload/selection process.
Here
I am using Custom validator to call the function. You can
use this JavaScript directly on click of a button or
FileUpload control.
<html
xmlns="http://www.w3.org/1999/xhtml">
<head
id="Head1" runat="server">
<title>Untitled
Page</title>
<script
type="text/javascript">
function
ValidateFile(Source, args)
{
var
FileUploadCtrl = document.getElementById('FileUpload1');
var FilePath = FileUploadCtrl.value;
//
var Extension = FilePath.substring(FilePath.lastIndexOf('.')
+ 1).toLowerCase();
if (Extension == "jpg" ||
Extension == "gif" || Extension == "png")
{
args.IsValid = true;
}
else
{
args.IsValid = false;
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:FileUpload ID="FileUpload1"
runat="server" />
<asp:CustomValidator
ID="CustomValidator1" runat="server" ErrorMessage="Please
select a valid doc or jpeg file"
ControlToValidate="FileUpload1"
ClientValidationFunction="ValidateExcelFile"></asp:CustomValidator>
<br />
<br />
<asp:Button ID="Button1" runat="server" Text="Button"
/>
</div>
</form>
</body>
</html>