telerik asyncupload control io exception

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ASP.NET

Ajax

File-Upload

Telerik

I am using telerik asyncupload control to upload files but the control is just loading one file and after that it is giving io exception saying parameter not found.

<telerik:RadAsyncUpload ID="AsyncUpload1" runat="server" ChunkSize="0"       TemporaryFolder="~/logos">
                                </telerik:RadAsyncUpload>
                                    <asp:Button ID="btnUpload" runat="server"   Text="Upload" onClick="btnUpload_Click" CssClass="about-btn" />
and in code

foreach (UploadedFile f in AsyncUpload1.UploadedFiles)
            {
                string temp;

                temp = "~/logos/" + f.FileName.ToString();
                AsyncUpload1.TargetFolder = temp;
                f.SaveAs(Server.MapPath(temp));
}