Frank's Blog

<asp:FileUpload ID="FileUpload1" runat="server" Width="100%"

 onchange="return checkFileExtension(this);" />

<script language="javascript">

   //傳入的elem必須是檔案的完整路徑

    function checkFileExtension(elem) 

    {

        var filePath = elem.value;

        if (filePath.indexOf('.') == -1) 

        {

            remove(elem);

            alert('不正確的副檔名格式');

            return false;

        }

        var validExtensions = new Array();

        var ext = filePath.substring(filePath.lastIndexOf('.') + 1).toLowerCase();

        validExtensions[0] = 'tif';

        validExtensions[1] = 'tiff';

        validExtensions[2] = 'pdf';

        for (var i = 0; i < validExtensions.length; i++)

        {

            if (ext == validExtensions[i])

            return true;

        }

        remove(elem);

        alert('不正確的副檔名格式： ' + ext.toUpperCase());

        return false;

    }

    function remove(control) 

    { 

        var who = control; 

        who.value = ""; 

        var who2 = who.cloneNode(false); 

        who2.onchange = who.onchange; 

        who.parentNode.replaceChild(who2, who); 

    }

</script>