.net C#,access,MDB数据库BLOB二进制字段的读写

BLOB二进制字段读写，一致是一个十分麻烦的事情，本人在总结前人的基础，特对access,MDB数据库BLOB的读写总结如下：




using System.Data;


using System.Data.OleDb;


using System.Windows.Forms;


using System.IO;




namespace Book




...{




/**//// <summary>


/// Db_Class 的摘要说明。


/// </summary>


public class Db_Class




...{


private OleDbConnection Conn;


private OleDbCommand cmd;


//构造函数


public Db_Class(String MDBFileName, String Password)




...{




String Str = string.Format("Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Jet Oledb:Database Password={1}", MDBFileName, Password);


Conn = new OleDbConnection(Str); //连接数据库,Password是MDB的密码


//by 闫磊 Email:Landgis@126.com,yanleigis@21cn.com 2007.10.13




}


//打开数据源链接


public OleDbConnection Db_Conn()




...{


Conn.Open();


return Conn;


}


//返回DataReader数据集，下面的SQL可以动态生成


public OleDbDataReader Db_CreateReader(string SQL)




...{


try




...{


cmd = new OleDbCommand(SQL, Conn);


OleDbDataReader Rs = cmd.ExecuteReader();




return Rs;


}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return null;




}


}


//返回DataReader数据集，下面的SQL是存储过程


public OleDbDataReader Db_CommandReader(string SQL)




...{


try




...{




cmd = new OleDbCommand(SQL, Conn);


cmd.CommandType = CommandType.StoredProcedure;


OleDbDataReader Rs = cmd.ExecuteReader();


return Rs;


}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return null;


}




}


//返回数据DataSet数据集


public DataSet Db_CreateDataSet(string SQL)




...{


try




...{


cmd = new OleDbCommand(SQL, Conn);


OleDbDataAdapter Adpt = new OleDbDataAdapter(cmd);


DataSet Ds = new DataSet();


Adpt.Fill(Ds, "NewTable");


return Ds;


}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return null;


}




}


//返回数据DataReader数据集，不需要返回数据的修改，删除可以使用本函数


public bool Db_ExecuteNonquery(string SQL)




...{


try




...{


Db_Conn();


cmd = new OleDbCommand(SQL, Conn);


try




...{


cmd.ExecuteNonQuery();




return true;


}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return false;


}


}


finally




...{




this.close();


}




}


//返回数据DataReader数据集，不需要返回数据的修改，删除可以使用本函数


public bool Db_ExecuteNonquery(string SQL, bool Connect)




...{


try




...{


if (Connect)


Db_Conn();


cmd = new OleDbCommand(SQL, Conn);


try




...{


cmd.ExecuteNonQuery();




return true;


}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return false;


}


}


finally




...{


if (Connect)


this.close();


}




}


//返回数据DataReader数据集，返回数据


public String Db_Executequery(string SQL)




...{


try




...{


Db_Conn();


cmd = new OleDbCommand(SQL, Conn);


try




...{


return cmd.ExecuteScalar().ToString();






}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return "";


}


}


finally




...{


this.close();


}




}


//返回数据DataReader数据集，返回数据


public String Db_Executequery(string SQL,String parent, bool connect)




...{


try




...{


if (connect)


Db_Conn();


cmd = new OleDbCommand(SQL, Conn);


try




...{


return cmd.ExecuteScalar().ToString();






}


catch (Exception ex)




...{


MessageBox.Show("parent:" + parent + "错误:因" + ex.Message + ",无法执行:" + SQL);


return "";


}


}


finally




...{


if (connect)


this.close();


}




}


//返回blob数据


public MemoryStream getBlob(string SQL)




...{


try




...{


Db_Conn();


cmd = new OleDbCommand(SQL, Conn);


cmd.CommandType = CommandType.Text;//是sql


OleDbDataReader Rs = cmd.ExecuteReader();


if (Rs.Read()) //循环到下一条记录




...{


if (!(Rs.GetValue(0) is System.DBNull))




...{


byte[] image_bytes = (byte[])Rs.GetValue(0);


MemoryStream ms = new MemoryStream(image_bytes);


return ms;


}


else


return null;


}


else


return null;




}




finally




...{


this.close();


}






}


//设置blob


public bool SetBlob(string SQL, MemoryStream Ms)




...{


try




...{


Db_Conn();




cmd = new OleDbCommand(SQL, Conn);


cmd.CommandType = CommandType.Text;//是sql




int n=Convert.ToInt32(Ms.Length.ToString());


Ms.Position = 0;


byte[] pReadByte = new Byte
;


Ms.Read(pReadByte, 0, n);




cmd.Parameters.Add("BLOB", OleDbType.Binary).Value = pReadByte;


cmd.ExecuteNonQuery();




return true;




}


catch (Exception ex)




...{


MessageBox.Show("错误:因" + ex.Message + ",无法执行:" + SQL);


return false;


}




finally




...{


this.close();


}






}






//关闭数据链接


public void close()




...{


Conn.Close();


}




}


}



说明:

1、getBlob(string SQL)是读BLOB字段，调用例子如下


//by 闫磊 Email:Landgis@126.com,yanleigis@21cn.com 2007.10.23


String sqlStr = "select content from dp where id=" + ID;//content为dp中的BLOB字段,ID为主键


MemoryStream ms = DBClass.getBlob(sqlStr);


if (ms == null)


richTextBox.Clear();


else




...{


if (ms.Length > 0)




...{


ms.Position = 0;


try




...{


richTextBox.LoadFile(ms, RichTextBoxStreamType.RichText);


}


catch




...{


richTextBox.LoadFile(ms, RichTextBoxStreamType.PlainText);


}


}


else


richTextBox.Clear();


}

2、BLOB二进制的写，SetBlob(string SQL, MemoryStream Ms),调用如下


private void SaveData(int ID1)




...{


String sqlStr = "update dp set content=:BLOB where id=" + ID;


MemoryStream ms = new MemoryStream();


richTextBox.SaveFile(ms, RichTextBoxStreamType.RichText);


if (!DBClass.SetBlob(sqlStr, ms))




...{


MessageBox.Show("保存失败");


}




}