功能：
1。把图片文件(JPG GIF PNG)上传，
2。保存到指定的路径（在web.config中设置路径，以文件的原有格式保存），
3。并自动生成指定宽度的（在web.config中设置宽度）
4。和指定格式的（在web.config中指定缩略图的格式）
5。和原图比例相同的缩略图(根据宽度和原图的宽和高计算所略图的高度)
6。可以判断是否已经存在文件
7。如果不覆盖，则给出错误
8。如果选中"覆盖原图"checkbox，则覆盖原图。
9。可以根据要求，在webform上设置1个以上的file input和相应的checkbox
10。并在文件上传完毕后，显示原图的文件名，尺寸，字节，和
11。缩略图的文件名尺寸。
12。缩略图的文件名格式：原图+"_thumb."+指定格式，如：test.jpg_thumb.gif,以便于管理。
--------------------
public void UploadFile(object sender, System.EventArgs e)
{
string imgNameOnly, imgNameNoExt, imgExt;
string imgThumbnail;
int erroNumber = 0;
System.Drawing.Image oriImg, newImg;
string strFePicSavePath = ConfigurationSettings.AppSettings["FePicSavePath"].ToString();
string strFePicThumbFormat = ConfigurationSettings.AppSettings["FePicThumbFormat"].ToString().ToLower();
int intFeThumbWidth = Int32.Parse(ConfigurationSettings.AppSettings["FePicThumbWidth"]);
string fileExt;
StringBuilder picInfo = new StringBuilder();
if(Page.IsValid)
{
for(int i = 0;i < Request.Files.Count; i++)
{
HttpPostedFile PostedFile = Request.Files[i];
fileExt = (System.IO.Path.GetExtension(PostedFile.FileName)).ToString().ToLower();
imgNameOnly = System.IO.Path.GetFileName(PostedFile.FileName);
if(fileExt == ".jpg" || fileExt == ".gif" || fileExt == ".png")
{
if(System.IO.File.Exists(strFePicSavePath + imgNameOnly) && (checkboxlistRewrite.Items[i].Selected == false))
{
erroNumber = erroNumber + 1;
picInfo.Append("错误：文件("+ (i+1) +") " + imgNameOnly + " 已经存在，请修改文件名
" );
}
}
else
{
erroNumber = erroNumber + 1;
picInfo.Append("错误：文件("+ (i+1) +") " + imgNameOnly + " 扩展名 " + fileExt + " 不被许可
" );
}
}
if(erroNumber > 0)
{
picInfo.Append("全部操作均未完成，请修改错误，再进行操作
");
}
else
{
for(int i = 0;i < Request.Files.Count; i++)
{
HttpPostedFile PostedFile = Request.Files[i];
imgNameOnly = System.IO.Path.GetFileName(PostedFile.FileName);
imgNameNoExt = System.IO.Path.GetFileNameWithoutExtension(PostedFile.FileName);
imgExt = System.IO.Path.GetExtension(PostedFile.FileName).ToString().ToLower();
oriImg = System.Drawing.Image.FromStream(PostedFile.InputStream);
newImg = oriImg.GetThumbnailImage(intFeThumbWidth, intFeThumbWidth * oriImg.Height/oriImg.Width,null,new System.IntPtr(0));
switch(imgExt)
{
//case ".jpeg":
case ".jpg":
oriImg.Save(strFePicSavePath + imgNameOnly , System.Drawing.Imaging.ImageFormat.Jpeg);
break;
case ".gif":
oriImg.Save(strFePicSavePath + imgNameOnly , System.Drawing.Imaging.ImageFormat.Gif);
break;
case ".png":
oriImg.Save(strFePicSavePath + imgNameOnly , System.Drawing.Imaging.ImageFormat.Png);
break;
}
//oriImg.Save(ConfigurationSettings.AppSettings["FePicSavePath"] + imgNameNoExt + ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
switch(strFePicThumbFormat)
{
//jpeg format can get the smallest file size, and the png is the largest size
//case "jpeg":
case "jpg":
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.jpg",System.Drawing.Imaging.ImageFormat.Jpeg);
imgThumbnail = imgNameOnly + "_thumb.jpg";
break;
case "gif":
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.gif",System.Drawing.Imaging.ImageFormat.Gif);
imgThumbnail = imgNameOnly + "_thumb.gif";
break;
case "png":
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.png",System.Drawing.Imaging.ImageFormat.Png);
imgThumbnail = imgNameOnly + "_thumb.png";
break;
default:
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.jpg",System.Drawing.Imaging.ImageFormat.Jpeg);
imgThumbnail = imgNameOnly + "_thumb.jpg";
break;
}//switch
picInfo.Append("文件 名：" + imgNameOnly + " ( " + oriImg.Width + " x " + oriImg.Height + " ) " + PostedFile.ContentLength/1024 + "KB
");
picInfo.Append("缩略图名：" + imgThumbnail + " ( " + newImg.Width + " x " + newImg.Height + " )
");
oriImg.Dispose();
newImg.Dispose();
}//for
picInfo.Append("所有操作成功
");
}// if erronumber = 0
}
else
{
picInfo.Append("有错误，请检查。操作未成功
");
}
lblPicInfo.Text = picInfo.ToString();
}