本文介绍了一种在ASP.NET中下载文件的方法。 方法一：可能是最简单的、最短的方式：
Response.ContentType = "application/pdf";
Response.AppendHeader("Content-Disposition", "attachment; filename=MyFile.pdf");
Response.TransmitFile(Server.MapPath("~/Files/MyFile.pdf"));
Response.End();
第一步是设置文档内容的类型，上面的例子是下载一个.PDF格式的文件。下面是最常用的一些文档内容类型：
.htm, .html Response.ContentType = "text/HTML";
.txt Response.ContentType = "text/plain";
.doc, .rtf, .docx Response.ContentType = "Application/msword";
.xls, .xlsx Response.ContentType = "Application/x-msexcel";
.jpg, .jpeg Response.ContentType = "image/jpeg";
.gif Response.ContentType = "image/GIF";
.pdf Response.ContentType = "application/pdf";
方法二：解决.PDF文件较大时，可能导致所下载的PDF文件无法打开的方案
protected void Button1_Click(object sender, EventArgs e)
{
string path;
try
{
path = Request.PhysicalApplicationPath + "/" + Session["pdfpath"].ToString() + "/PDF/" + Session["mlmc"].ToString() + ".pdf";
}
catch (Exception)
{
return;
}
System.IO.Stream iStream = null;
byte[] buffer = new Byte[];
int length;
long dataToRead;
string filename = Session["mlmc"].ToString() + ".pdf"; try
{
iStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
dataToRead = iStream.Length;
Response.Clear();
Response.ClearHeaders();
Response.ClearContent();
Response.ContentType = "application/pdf"; //文件类型
Response.AddHeader("Content-Length", dataToRead.ToString());//添加文件长度，进而显示进度
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));
while (dataToRead > )
{
if (Response.IsClientConnected)
{
length = iStream.Read(buffer, , );
Response.OutputStream.Write(buffer, , length);
Response.Flush(); buffer = new Byte[];
dataToRead = dataToRead - length;
}
else
{
dataToRead = -;
}
} }
catch (Exception ex)
{
Response.Write("文件下载时出现错误!");
}
finally
{
if (iStream != null)
{
iStream.Close();
}
//结束响应，否则将导致网页内容被输出到文件，进而文件无法打开
Response.End();
}
}
通过以上代码，可在浏览器中打开一个“打开/保存”对话框来下载并保存文件。