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>