ASP.NET - 上传图片方法（单张）

/// <summary>
/// 上传图片
/// </summary>
/// <param name="fileupload">上传的控件</param>
/// <param name="folder">要存储的文件夹（要在服务器已经存在）</param>
/// <param name="imageName">图片名称</param>
/// <returns></returns>
public string UploadImage(FileUpload fileupload, string folder, string imageName)
{
Boolean fileOK = false;
String path = Server.MapPath("~/" + folder + "/");
if (fileupload.HasFile)
{
String fileExtension =
System.IO.Path.GetExtension(fileupload.FileName).ToLower();
String[] allowedExtensions = { ".gif", ".png", ".jpeg", ".jpg" };
for (int i = 0; i < allowedExtensions.Length; i++)
{
if (fileExtension == allowedExtensions[i])
{
fileOK = true;
}
}
}
else
{
return "请选择要上传的文件！";
}

if (fileOK)
{
try
{
string ImagesPath = path + imageName + Path.GetExtension(fileupload.FileName);
fileupload.PostedFile.SaveAs(ImagesPath);
return "上传成功！";
}
catch
{
return "上传失败！";
}
}
else
{
return "只能上传 .gif, .png, .jpeg, .jpg 等类型图片！";
}
}