IMAGE TYPE VALIDATION IN FILE UPLOAD CONTROL

IMAGE TYPE VALIDATION IN FILE UPLOAD CONTROL
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<td>
<asp:FileUpload ID="FileUpload1" runat="server" CssClass="textbox_reg" Width="210px" />
<asp:RegularExpressionValidator ID="rfv_FileUpload1" runat="server" ErrorMessage="Invalid file name! select only image file types."
ValidationExpression=".*(\.[Jj][Pp][Gg]|\.[Gg][Ii][Ff]|\.[Pp][Nn][Gg]|\.[Jj][Pp][Ee][Gg]|\.[Bb][Mm][Pp])"
Display="None" ControlToValidate="FileUpload1">*</asp:RegularExpressionValidator>

<cc1:ValidatorCalloutExtender ID="vce_imagebefore1" TargetControlID="rfv_FileUpload1" runat="server">
</cc1:ValidatorCalloutExtender>
</td>