How to Validate file type in FileUpload Control in ASP.NET

In this tutorial, how to validate File Upload Control to upload only images using Regular Expressing Validation Control in Asp.Net.

First add File Upload Control to Asp.Net web page.

<asp:FileUpload ID="fileuploaduserphoto" runat="server" />

Now, add following Regular Expression Validation control to Asp.Net Webpage.

 <asp:RegularExpressionValidator runat="server" ID="valUpTest" ControlToValidate="fileuploaduserphoto" ValidationGroup="up"
            ErrorMessage="Image Files Only (.jpg, .png, .gif)"
            ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))(.jpg|.JPG|.gif|.GIF|.jpeg|.JPEG|.png|.PNG)$" />

The complete source code

<asp:FileUpload ID="fileuploaduserphoto" runat="server" />
        <asp:RegularExpressionValidator ForeColor="Red" runat="server" ID="valUpTest" Display="Dynamic"
            ControlToValidate="fileuploaduserphoto" ValidationGroup="up" ErrorMessage="Image Files Only (.jpg, .png, .gif)"
            ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))(.jpg|.JPG|.gif|.GIF|.jpeg|.JPEG|.png|.PNG)$" /><br />
        <asp:Button ValidationGroup="up" ID="Button1" runat="server" Text="Upload" OnClick="Button1_Click" />

Demo

Download Complete Source Code Demo