protected void Upload()
        {

            //判断是否选择文件
            if (FileUpload1.HasFile)
            {

                string fileContentType = FileUpload1.PostedFile.ContentType;//获取文件类型
                //判断类型是否符合条件
                if (fileContentType == "image/bmp" || fileContentType == "image/gif" || fileContentType == "image/pjpeg"||fileContentType=="image/PNG")
                {

                    //客户端文件路径
                    string name = FileUpload1.PostedFile.FileName;
                    FileInfo file = new FileInfo(name);
                    //文件名称
                    string fileName = file.Name;
                    //服务器端文件路径
                    string webFilePath = Server.MapPath("resource/" + fileName);
                    //判断同名文件是否存在
                    if (!File.Exists(webFilePath))
                    {

                        try
                        {

                            //使用SaveAs方法保存文件
                            FileUpload1.SaveAs(webFilePath);
                            this.lMsg.Text = "提示：文件" + fileName + "上传成功！";
                            this.lPathInfo.Text = "resource" + fileName;
                            this.iPic.ImageUrl = "resource" + fileName;
                        }
                        catch (Exception ex)
                        {

                            this.lMsg.Text = "提示:文件上传失败，失败原因：" + ex.Message;
                        }
                    }
                    else
                    {

                        this.lMsg.Text = "提示：文件已经存在，请重命名后上传";
                    }
                }
                else
                {

                    this.lMsg.Text = "提示：文件类型不符合";
                }
            }
        }
        protected void btUpload_Click(object sender, EventArgs e)
        {

            if (Directory.Exists("resource"))
            {

                Upload();
            } 
            else
            {

                
                Directory.CreateDirectory(Server.MapPath("resource"));
                Upload();
            }
            

        }

本文转自蓬莱仙羽51CTO博客，原文链接：http://blog.51cto.com/dingxiaowei/1366648，如需转载请自行联系原作者