通过Ajax调用通过Web方法从C#下载文件？

[System.Web.Services.WebMethod()]
public static string GetServerDateTime(string msg)
{
    String result = "Result : " + DateTime.Now.ToString() + " - From Server";
    System.IO.FileInfo file = new System.IO.FileInfo(System.Web.HttpContext.Current.Server.MapPath(System.Configuration.ConfigurationManager.AppSettings["FolderPath"].ToString()) + "" + "Default.aspx");
    System.Web.HttpResponse Response = System.Web.HttpContext.Current.Response;
    Response.ClearContent();
    Response.AddHeader("Content-Disposition","attachment; filename=" + file.Name);
    Response.AddHeader("Content-Length",file.Length.ToString());
    Response.ContentType = "application/octet-stream";
    Response.WriteFile(file.FullName);
    //HttpContext.Current.ApplicationInstance.CompleteRequest();
    Response.Flush();
    Response.End();
    return result;        
}

我的ajax调用代码如下

<script type="text/javascript">
    function GetDateTime() {
                    var params = "{'msg':'From Client'}";
                    $.ajax
                      ({
                          type: "POST",url: "Default.aspx/GetServerDateTime",data: params,contentType: "application/json;charset=utf-8",dataType: "json",success: function (result) {
                              alert(result.d);
                          },error: function (err) {

                          }
                      });
    }
</script>

我点击按钮调用此功能..

我不知道如何使用其他方法下载文件

如果有其他可用的方法,请建议我或使用相同的代码进行更正.

谢谢大家..