Verify the regular expression of the FileUpload upload file name extension

<script type= "Text/javascript" >

function Checkfile (str)

{

var Strregex = "(. Jpg|. Jpg|. Gif|. GIF) $ "; Regular expression to validate the picture extension

var re=new RegExp (Strregex);

if (Re.test (str)) {

return (true);

}

else{

Alert ("Forbidden file name extension");

return (false);

}

}

</script>

<input id= "File1" type= "file" onchange= "Checkfile (this.value);"/>

<br/>

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<asp:fileupload id= "FileUpload1" runat= "Server" onchange= "Checkfile" (this.value); "/>

<br/>

<br/>

<asp:fileupload id= "FileUpload2" runat= "Server"/>

<asp:regularexpressionvalidator id= "RegularExpressionValidator1" runat= "Server" controltovalidate= "FileUpload2" "Errormessage=" must be a JPG or gif file "validationexpression=" ^ ([a-za-z]:) | {2}/w+)/$?) (///(/w[/w].*)) (. Jpg|. Jpg|. Gif|. GIF) $ >

</asp:RegularExpressionValidator>

<br/>

<br/>

<asp:button id= "Button1" runat= "server" text= "upload"/>