C# 上传下载文件

protected void btnFileUpload_Click(object sender, EventArgs e)
    {
        int fileSize = FileUpload1.PostedFile.ContentLength;
        //string fileName = FileUpload1.PostedFile.FileName; //全路径
        string fileName = Path.GetFileName(FileUpload1.PostedFile.FileName);
        if (fileName != "")
        {
            //True不存在同名文件
            bool flag = IsExistSameFile(Server.MapPath("..\\FilesPublic"), fileName);
            if (flag)
            {
                FileUpload1.PostedFile.SaveAs(Server.MapPath("..\\FilesPublic\\") + fileName);

            }

        }

    }

    //文件夹中是否存在同名文件

    public bool IsExistSameFile(string filePath, string fileName)
    {
        bool flag = true;
        FileInfo[] NewFileInfo;//定义一个数组，储存找到的文件并作为返回值
        DirectoryInfo FatherDirectory = new DirectoryInfo(filePath); //创建一个当前目录的实例
        NewFileInfo = FatherDirectory.GetFiles();
        //遍历文件夹
        foreach (FileInfo NextFolder in NewFileInfo)
        {
            if (fileName == NextFolder.Name)
            {
                flag = false;
            }
        }
        return flag;
    }



    //下载文件，弹出另存为对话框

    protected void lbDownLoad_Click(object sender, EventArgs e)
    {
        LinkButton lb = (LinkButton)sender;
        string id = lb.CommandArgument;
        DataSet ds = WFInfo.Business.FileManager.FileNameByID(id);
        string fileName = ds.Tables[0].Rows[0]["FileName"].ToString();

        string filepath = Server.MapPath("../FilesPublic/" + fileName);
        string filename = System.IO.Path.GetFileName(filepath);
        Response.Clear();
        Response.ContentType = "application/octet-stream";
        Response.AppendHeader("Content-Disposition", "attachment;filename=" + filename);
        Response.TransmitFile(filepath);
        Response.Flush();
        Response.Close();
    }