fileupload control with ajax

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ASP.NET

Ajax

I am using ajax tab control in aspx page.
In that control i am using fileupload control to upload the image.
but fileupload control is not able to get any file.

if(fileupload1.hasfile==true)
{
string f=filupload1.filename.tostiring();
string fpath="~/image/image/"+f;
fileupload1.saveas(mappath(fpath));
}

but it doesnot able take file.
so m getting error in if condition.

can any one help me out.
thankx in advance.