ASP.NET中如何检测一个图片是否是真实图片 防范病毒上传

主要是用来判断客户端上传的图片是否为真实的图片，以防病毒侵入，保证上传的文件的安全。

 

主要代码如下：

需要引用

[csharp]
using system.io; 

using system.io;

[csharp]
public void uploadfile() 
{ 
try 
            {  
                httppostedfile postfile = request.files["file"];  
                string savepath = server.mappath("image/" + postfile.filename); 
                postfile.saveas(savepath);  
                filestream fs = new filestream(savepath, filemode.open, fileaccess.read); 
                binaryreader reader = new binaryreader(fs);  
                string fileclass;  
                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(); 
                 
                if (fileclass == "255216" || fileclass == "7173" || fileclass == "6677" || fileclass == "13780") 
                { 
                    //255216是jpg;7173是gif;6677是bmp,13780是png;7790是exe,8297是rar   
                    //response.write("图片可用");   
                    //保存到中  
                }  
                else 
                {  
                    //response.write("图片非法");   
                    file.delete(savepath); //删除文件  
                    return;  
                }  
            }  
            catch (exception) 
            { //response.write("图片非法！");   
                return;  
                throw;  
            } 
} 

public void uploadfile()
{
try
            {
                httppostedfile postfile = request.files["file"];
                string savepath = server.mappath("image/" + postfile.filename);
                postfile.saveas(savepath);
                filestream fs = new filestream(savepath, filemode.open, fileaccess.read);
                binaryreader reader = new binaryreader(fs);
                string fileclass;
                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();
               
                if (fileclass == "255216" || fileclass == "7173" || fileclass == "6677" || fileclass == "13780")
                {
                    //255216是jpg;7173是gif;6677是bmp,13780是png;7790是exe,8297是rar
                    //response.write("图片可用");
                    //保存到数据库中
                }
                else
                {
                    //response.write("图片非法");
                    file.delete(savepath); //删除文件
                    return;
                }
            }
            catch (exception)
            { //response.write("图片非法！");
                return;
                throw;
            }
}
mvc 中的代码如下，在这里我返回的json格式，当然可以返回content或其他：

 

 

[csharp]
/// <summary>  
        /// 上传头像  
        /// </summary>  
        /// <param name="userid">用户编号</param>  
        /// <returns>json(-1表示异常，-2表示文件不合法)</returns>  
        [httppost]  
        public jsonresult uploadavatar(string userid) 
        { 
            //上传头像  
            string folderpath = "/upload/avatar/"; 
            //判断路径是否存在  
            if (!directory.exists(folderpath)) 
                directory.createdirectory(folderpath);//创建文件路径  
            httppostedfilebase uploadfile = request.files["avatars"]; 
            if (uploadfile != null) 
            { 
                string orifilename = uploadfile.filename;//原始文件名  
                string filename = userid + "_" + orifilename; 
                uploadfile.saveas(server.mappath(folderpath + filename)); 
                filestream fs = new filestream(server.mappath(folderpath + filename), filemode.open, fileaccess.read); 
                binaryreader reader = new binaryreader(fs); 
                string fileclass; 
                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(); 
                if (fileclass == "255216" || fileclass == "7173" || fileclass == "6677" || fileclass == "13780") 
                { 
                    //255216是jpg;7173是gif;6677是bmp,13780是png;7790是exe,8297是rar   
                    //response.write("图片可用");   
                    //保存到数据库中  
                } 
                else 
                { 
                    
                    //response.write("图片非法");   
                    fileinfo f = new fileinfo(server.mappath(folderpath + filename)); 
                    f.delete(); //删除文件  
                    return json(-2, jsonrequestbehavior.allowget); 
                } 
                return json(server.htmlencode(folderpath + filename), jsonrequestbehavior.allowget); 
            } 
            return json(-1, jsonrequestbehavior.allowget); 
 
        } 

/// <summary>
        /// 上传头像
        /// </summary>
        /// <param name="userid">用户编号</param>
        /// <returns>json(-1表示系统异常，-2表示文件不合法)</returns>
        [httppost]
        public jsonresult uploadavatar(string userid)
        {
            //上传头像
            string folderpath = "/upload/avatar/";
            //判断路径是否存在
            if (!directory.exists(folderpath))
                directory.createdirectory(folderpath);//创建文件路径
            httppostedfilebase uploadfile = request.files["avatars"];
            if (uploadfile != null)
            {
                string orifilename = uploadfile.filename;//原始文件名
                string filename = userid + "_" + orifilename;
                uploadfile.saveas(server.mappath(folderpath + filename));
                filestream fs = new filestream(server.mappath(folderpath + filename), filemode.open, fileaccess.read);
                binaryreader reader = new binaryreader(fs);
                string fileclass;
                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();
                if (fileclass == "255216" || fileclass == "7173" || fileclass == "6677" || fileclass == "13780")
                {
                    //255216是jpg;7173是gif;6677是bmp,13780是png;7790是exe,8297是rar
                    //response.write("图片可用");
                    //保存到数据库中
                }
                else
                {
                  
                    //response.write("图片非法");
                    fileinfo f = new fileinfo(server.mappath(folderpath + filename));
                    f.delete(); //删除文件
                    return json(-2, jsonrequestbehavior.allowget);
                }
                return json(server.htmlencode(folderpath + filename), jsonrequestbehavior.allowget);
            }
            return json(-1, jsonrequestbehavior.allowget);

        }