Description:


The below javascript funtion checks the browsing file. For example, If 

the uploading file should accept only excel and word documents like that, 

then in that scenario, we can use this function.



<script type="text/javascript">
    function CheckFileExtension()
    {
        var ctrlUpload = document.getElementById('< %=FileUpload.ClientID% >');

        
        //Does the user browse or select a file or not
        if (ctrlUpload.value =='' )
        {
            alert("Select a file to upload!");
            ctrlUpload.focus();
            return false;
        }

         
        //Extension List for validation. Add your 
           required extension here with comma separator 
        var extensionList = new Array(".xls", ".doc");
        
        //Get Selected file extension
        var extension = ctrlUpload.value.slice(ctrlUpload.value.indexOf(".")).toLowerCase();

        
        //Check file extension with your required extension list.
        for (var i = 0; i < extensionList.length; i++)
        {
            if (extensionList[i] == extension)
            return true;
        }
        alert("You can only upload below File Type:\n\n"+extensionList.join("\n"));
        ctrlUpload.focus();
        return false;
   }
   
   
   
   </script>