尝试上载文件时出现System.UnauthorizedAccessException

Question

我正在尝试从localhost中的计算机下载文件。但我一直在收到错误

System.UnauthorizedAccessException：拒绝访问路径'c：\ users \ zunair \ documents \ visual studio 2012 \ Projects \ WebApplication2 \ WebApplication2 \ Uploads'。

这是我的代码

if (FileExt == ".pdf")
{
    Response.ContentType = "Application/pdf";
    Response.AppendHeader("Content-Disposition", "attachment; filename=FileName");
    Response.TransmitFile(Server.MapPath("~/Uploads" + FileName));
    Response.End();
}

我在Response.TransmitFile(Server.MapPath("~/Uploads" + FileName));

收到错误