取得文件真正扩展名类型

实现这个功能，需要使用一个System.IO名称空间。只需判断文件流前两个字节即可。

参考代码：

View Code

string GetFileCass( string path)
    {
         try
        {
            FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read);
            BinaryReader reader = new BinaryReader(fs);
             string fileClass = string .Empty;
             byte buffer;

             byte [] b = new byte [ 2 ];
            buffer = reader.ReadByte();
            b[ 0 ] = buffer;
            fileClass = buffer.ToString();
            buffer = reader.ReadByte();
            b[ 1 ] = buffer;
            fileClass += buffer.ToString();
            reader.Close();
            fs.Close();

             return fileClass;
        }
         catch
        {
             return string .Empty;
        }
    }

例子演示：

< asp:FileUpload ID ="FileUpload1" runat ="server" /> 
 < asp:Button ID ="Button1" runat ="server" Text ="Get File Extension Info" onclick ="Button1_Click" /> 
 
 < asp:Label ID ="lblExtension" runat ="server" Text ="" ></ asp:Label > 
 < asp:Label ID ="lblFileClass" runat ="server" Text ="" ></ asp:Label >

按钮事件:

View Code

protected void Button1_Click( object sender, EventArgs e)
    {
         if ( ! File.Exists( this .FileUpload1.PostedFile.FileName))
        {
             // follow Js class, download address: http://www.cnblogs.com/insus/articles/1341703.html
            Insus.NET.InsusJsUtility objJs = new Insus.NET.InsusJsUtility();
            objJs.JsAlert( " You did not specify a file. " );
             return ;
        }

         string path = this .FileUpload1.PostedFile.FileName;
         this .lblExtension.Text = " Extension: " + path.Substring(path.LastIndexOf( " . " ));
         this .lblFileClass.Text = " FileClass: " +   GetFileCass(path);
    }

选择一个Excel文件得到的结果：

取得文件真正扩展名类型

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取得文件真正扩展名类型

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