Regular expression validation to validate image and excel file type

Following code validates the excel and image file to upload using file upload control in asp.net. we are validating it using Required field validator and Regular Expression validator control of asp.net.


Example :

<div class="containor">
        <div class="row-fluid">
            <div class="span8">
                <asp:FileUpload ID="flUploadExcel" CssClass="span12" runat="server" />
            </div>
            <div class="span4">
                <asp:RequiredFieldValidator ID="RequiredFieldValidator1" ControlToValidate="flUploadExcel" Display="Dynamic" ErrorMessage="Please enter the excel file!" ToolTip="Please enter the excel file" runat="server"></asp:RequiredFieldValidator>
                <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" Display="Dynamic" ErrorMessage="Upload Excel only." ValidationExpression="^.*\.(xls|xlsx)$" ControlToValidate="flUploadExcel">
                </asp:RegularExpressionValidator>

            </div>
        </div>

         <div class="row-fluid">
            <div class="span8">
                <asp:FileUpload ID="flUploadImage" CssClass="span12" runat="server" />
            </div>
            <div class="span4">
                <asp:RequiredFieldValidator ID="RequiredFieldValidator2" ControlToValidate="flUploadImage" Display="Dynamic" ErrorMessage="Please enter an image file!" ToolTip="Please enter the excel file" runat="server"></asp:RequiredFieldValidator>
                <asp:RegularExpressionValidator ID="RegularExpressionValidator2" runat="server" Display="Dynamic" ErrorMessage="Upload image file only." ValidationExpression="^.*\.(jpg|jpeg|png|bmp|gif)$" ControlToValidate="flUploadImage">
                </asp:RegularExpressionValidator>

            </div>
        </div>
    </div>
    <div class="containor">
        <asp:Button ID="btnsubmit" class="defaultbutton" runat="server" Text="SUBMIT" OnClick="btnsubmit_Click" />
    </div>