C# 文件保存到数据库中或者从数据库中读取文件

//保存文件到SQL Server数据库中
FileInfo fi=new FileInfo(fileName);
FileStream fs=fi.OpenRead();
byte[] bytes=new byte[fs.Length];
fs.Read(bytes,0,Convert.ToInt32(fs.Length));
SqlCommand cm=new SqlCommand();
cm.Connection=cn;
cm.CommandType=CommandType.Text;
if(cn.State==0) cn.Open();
cm.CommandText="insert into "+tableName+"("+fieldName+") values(@file)";
SqlParameter spFile=new SqlParameter("@file",SqlDbType.Image);
spFile.Value=bytes;
cm.Parameters.Add(spFile);
cm.ExecuteNonQuery()
//保存文件到Access数据库中
FileInfo fi=new FileInfo(fileName);
FileStream fs=fi.OpenRead();
byte[] bytes=new byte[fs.Length];
fs.Read(bytes,0,Convert.ToInt32(fs.Length));
OleDbCommand cm=new OleDbCommand();
cm.Connection=cn;
cm.CommandType=CommandType.Text;
if(cn.State==0) cn.Open();
cm.CommandText="insert into "+tableName+"("+fieldName+") values(@file)";
OleDbParameter spFile=new OleDbParameter("@file",OleDbType.Binary);
spFile.Value=bytes;
cm.Parameters.Add(spFile);
cm.ExecuteNonQuery()
//保存客户端文件到数据库
sql="update t_mail set attachfilename=@attachfilename,attachfile=@attachfile where mailid="+mailid;
myCommand = new SqlCommand(sql, new SqlConnection(ConnStr));
string path = fl_name.PostedFile.FileName;
string filename=path.Substring(path.LastIndexOf("\\")+1,path.Length-path.LastIndexOf("\\")-1);
myCommand.Parameters.Add("@attachfilename",SqlDbType.VarChar);
myCommand.Parameters["@attachfilename"].Value=filename;
myCommand.Parameters.Add("@attachfile",SqlDbType.Image);
Stream fileStream = fl_name.PostedFile.InputStream;
int intFileSize = fl_name.PostedFile.ContentLength;
byte[] fileContent = new byte[intFileSize];
int intStatus = fileStream.Read(fileContent,0,intFileSize); //文件读取到fileContent数组中
myCommand.Parameters["@attachfile"].Value=((byte[])fileContent);
fileStream.Close();
myCommand.Connection.Open();
myCommand.ExecuteNonQuery();
myCommand.Connection.Close();

SqlDataReader dr=null;
SqlConnection objCn=new SqlConnection();
objCn.ConnectionString="Data Source=(local);User ID=sa;Password=;Initial Catalog=Test";
SqlCommand cm=new SqlCommand();
cm.Connection=cn;
cm.CommandType=CommandType.Text;
cm.CommandText="select "+fieldName+" from "+tableName+" where ID=1";
dr=cm.ExecuteReader();
byte[] File=null;
if(dr.Read())
{
File=(byte[])dr[0];
}
FileStream fs;
FileInfo fi=new System.IO.FileInfo(fileName);
fs=fi.OpenWrite();
fs.Write(File,0,File.Length);
fs.Close();

FileStream fs;
FileInfo fi=new System.IO.FileInfo(fileName);
fs=fi.OpenWrite();
fs.Write(File,0,File.Length);
fs.Close();
修改为
FileStream fs=new FileStream(fileName,FileMode.CreateNew);
BinaryWriter bw=new BinaryWriter(fs);
bw.Write(File,0,File.Length);
bw.Close();
fs.Close();