step 1 : Make a default.aspx page
put this script in to head section of html page.
<script>
function valid_file()
{
if(!ChkFile(document.getElementById(“fileupload1″)))
{
alert(‘Please Upload Image File’);
document.getElementById(“fileupload1″).focus();
return false;
}
}
function ChkFile(txtfield)
{
var filename,filenamelen
var fileext,fileextlen
var allowedtypes = [".jpg",".JPG",".jpeg",".JPEG",".BMP",".bmp"]
var dotpos
filename = txtfield.value
filenamelen = filename.length
dotpos = filename.lastIndexOf(“.”)
fileextlen = (filenamelen – dotpos – 1)
if (fileextlen >= 3 && fileextlen <= 4) //this allows files with a min of 3 and max of 4 chars in their extension
{
fileext = filename.substring(dotpos,filenamelen)
//alert (fileext)
for(var ctr=0;ctr<allowedtypes.length;ctr++)
{
if(allowedtypes[ctr] == fileext)
{
return true;
}
}
//alert(“Only JPG/JPEG/GIF type picture files are allowed.\n Please select a valid file type.”)
}
else
//alert(“The file you have selected is not a valid picture file.\nPlease select a different file.”)
return false
}
</script>
step 2 :On the default.aspx.vb page
add this code in to page load function
dont put this file in ispostback block
btnsubmit..Attributes.Add(“onclick”, “javascript:return valid_file();”)
