文件上传在asp.net中无效

Question

我正在尝试使用FileUpload上传文件，但它不起作用。单击按钮后，它会重新加载页面，但图像未保存

以下代码来自microsoft，但仍然无效

protected void uploadBtn_Click(object sender, EventArgs e)
    {

            Boolean fileOK = false;
            String path = Server.MapPath("~/Sources/images/");
            if (imageUpload.HasFile)
            {
                String fileExtension =
                    System.IO.Path.GetExtension(imageUpload.FileName).ToLower();
                String[] allowedExtensions = { ".gif", ".png", ".jpeg", ".jpg" };
                for (int i = 0; i < allowedExtensions.Length; i++)
                {
                    if (fileExtension == allowedExtensions[i])
                    {
                        fileOK = true;
                    }
                }
            }

            if (fileOK)
            {
                try
                {
                    imageUpload.PostedFile.SaveAs(path
                        + imageUpload.FileName);
                    statusUploadLbl.Text = "File uploaded!";
                }
                catch (Exception ex)
                {
                    statusUploadLbl.Text = "File could not be uploaded.";
                }
            }
            else
            {
                statusUploadLbl.Text = "Cannot accept files of this type.";
            }
    }

请帮忙，谢谢