功能：
1。把圖片文件(JPG GIF PNG)上傳，
2。保存到指定的路徑（在web.config中設(shè)置路徑，以文件的原有格式保存），
3。并自動生成指定寬度的（在web.config中設(shè)置寬度）
4。和指定格式的（在web.config中指定縮略圖的格式）
5。和原圖比例相同的縮略圖(根據(jù)寬度和原圖的寬和高計算所略圖的高度)
6?？梢耘袛嗍欠褚呀?jīng)存在文件
7。如果不覆蓋，則給出錯誤
8。如果選中"覆蓋原圖"checkbox，則覆蓋原圖。
9?？梢愿鶕?jù)要求，在webform上設(shè)置1個以上的file input和相應(yīng)的checkbox
10。并在文件上傳完畢后，顯示原圖的文件名，尺寸，字節(jié)，和
11?？s略圖的文件名尺寸。
12?？s略圖的文件名格式：原圖+"_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("<b>錯誤：</b>文件("+ (i+1) +") " + imgNameOnly + " 已經(jīng)存在，請修改文件名<br>" );
}
}
else
{
erroNumber = erroNumber + 1;
picInfo.Append("<b>錯誤：</b>文件("+ (i+1) +") " + imgNameOnly + " 擴(kuò)展名 " + fileExt + " 不被許可<br>" );
}

}

if(erroNumber > 0)
{
picInfo.Append("<font color=red>全部操作均未完成，請修改錯誤，再進(jìn)行操作</font><br>");
}
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("<b>文件　名：</b>" + imgNameOnly + " ( " + oriImg.Width + " x " + oriImg.Height + " ) " + PostedFile.ContentLength/1024 + "KB<br>");
picInfo.Append("<b>縮略圖名：</b>" + imgThumbnail + " ( " + newImg.Width + " x " + newImg.Height + " )<br><br>");

oriImg.Dispose();
newImg.Dispose();

}//for
picInfo.Append("<font color=red>所有操作成功</font><br>");

}// if erronumber = 0

}
else
{
picInfo.Append("<font color=red>有錯誤，請檢查。操作未成功</font><br>");

}

lblPicInfo.Text = picInfo.ToString();

}