.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
... {
    /**//// 

 
    /// Db_Class 的摘要说明。
    /// 

 
    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:[email protected],[email protected] 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[n];
                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:[email protected],[email protected] 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");
            }

        }