以下是实现附件上传，下载和删除功能的一段代码：

上传：

string[] strLst = fu_up.PostedFile.FileName.Split('\\');
string filename = strLst[strLst.Length-1];//读取附件的名字
if (filename != "")
{
fu_up.PostedFile.SaveAs("" + Server.MapPath(".\\upload\\") + "" + filename);
}

下载：

string filename = "111.jpg";
string mPath = "" + Server.MapPath(".\\upload\\") + "" +filename ;//取文件路径
this.txt_load.Text = mPath.ToString();
System.IO.FileInfo file = new System.IO.FileInfo(mPath);

if (file.Exists)
{

Response.Clear();

Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);

Response.AddHeader("Content-Length", file.Length.ToString());

Response.ContentType = "application/octet-stream";

Response.Filter.Close();

Response.WriteFile(file.FullName);

Response.End();
}

删除：

string filename = "111.jpg";
string path = "" + Server.MapPath(".\\upload\\") + "" + filename.ToString();
System.IO.FileInfo file = new System.IO.FileInfo(path);
if (file.Exists)
{
file.Delete();
}