We use file upload web control in our sites, where we want only valid image types to be uploaded.

Without talking much -> here are 3 ways to do it.

1. Accept attribute of fileUpload control - Doesnt work with most of the browsers (Bad with IE itself)

2. Regular Expression validator for FileUpload

<asp:RegularExpressionValidator id="UpLoadValidator" runat="server" ErrorMessage="Upload Images only." ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))(.jpg|.png|.bmp|.jpeg|.gif)$" ControlToValidate="FileUpload1"> </asp:RegularExpressionValidator>

This is Not very handy when using AJAX controls on page- Both javascripts dont like each other :)

3. Write a code behind function in a very simple way - Most robust way to use it. - Very Generic can be used for any file types.

private bool IsFileValid()

string [] allowedImageTyps = {"image/gif", "image/pjpeg", "image/bmp","image/x-png"};

StringCollection imageTypes = new StringCollection();

imageTypes.AddRange(allowedImageTyps);

if (imageTypes.Contains(FileUpload1.PostedFile.ContentType))

return true;

else

{

return false;

}

 NOTE - use FileUpload1.PostedFile.ContentType and not the file name to check the Extension

Leave a comment if this helped you