下载完后，给用户个提示
string name = @"c:\123.rar";
FileInfo aFile = new FileInfo(name);

Response.Clear();
Response.ClearHeaders();
Response.BufferOutput = false;
Response.ContentType = "application/octet-stream";
Response.AppendHeader("Content-disposition", "attachment;filename=" + HttpUtility.UrlEncode("123.rar", Encoding.UTF8));
Response.AddHeader("Content-Length", aFile.Length.ToString());
Response.WriteFile(name);
Response.Flush();

Response.End();

下载完后，想给用户一个提示框，提示下载成功

[解决办法]
try{
string name = @"c:\123.rar";
FileInfo aFile = new FileInfo(name);

Response.Clear();
Response.ClearHeaders();
Response.BufferOutput = false;
Response.ContentType = "application/octet-stream";
Response.AppendHeader("Content-disposition", "attachment;filename=" + HttpUtility.UrlEncode("123.rar", Encoding.UTF8));
Response.AddHeader("Content-Length", aFile.Length.ToString());
Response.WriteFile(name);
Response.Flush();

Response.End();

Response.Write("<script>alert('下载成功!');</script>");

}
catch{
Response.Write("<script>alert('下载失败!');</script>");
}
[解决办法]
在最后加上
Response.Write(" <script> alert('哈哈'); </script> ");
[解决办法]
RegisterClientScriptBlock("01","<script>alert('成功')</script>");
[解决办法]
Response.Write("<script>alert('下载完成！');</script>");
[解决办法]

C# code

Page.RegisterStartupScript("ALERT", <script language='javascript'>alert('DONE');</script>)