using System;
using System.IO;
using System.Collections;
using System.Data;
using System.Data.OleDb;  
namespace Exam_Manage.DAL
…{
    /**//// <summary>
    /// 试题数据访问基础类
    /// </summary>
    public abstract class DbSQL
    …{
        public DbSQL()
        …{
        }
        protected static string connectionString=@”provider=microsoft.jet.oledb.4.0; ” + “Data Source= ” +Directory.GetCurrentDirectory() + @”mdbdb.mdb”;
       
        执行简单SQL语句#region  执行简单SQL语句

        /**//// <summary>
        /// 执行SQL语句，返回影响的记录数
        /// </summary>
        /// <param name=”SQLString”>SQL语句</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSql(string SQLString)
        …{
            using (OleDbConnection connection = new OleDbConnection(connectionString))
            …{               
                using (OleDbCommand cmd = new OleDbCommand(SQLString,connection))
                …{
                    try
                    …{       
                        connection.Open();
                        int rows=cmd.ExecuteNonQuery();
                        return rows;
                    }
                    catch(System.Data.OleDb.OleDbException E)
                    …{                   
                        connection.Close();
                        throw new Exception(E.Message);
                    }
                }               
            }
        }
       
        /**//// <summary>
        /// 执行多条SQL语句，实现数据库事务。
        /// </summary>
        /// <param name=”SQLStringList”>多条SQL语句</param>       
        public static void ExecuteSqlTran(ArrayList SQLStringList)
        …{
            using (OleDbConnection conn = new OleDbConnection(connectionString))
            …{
                conn.Open();
                OleDbCommand cmd = new OleDbCommand();
                cmd.Connection=conn;
               
                OleDbTransaction tx=conn.BeginTransaction();           
                cmd.Transaction=tx;               
                try
                …{          
                    for(int n=0;n<SQLStringList.Count;n++)
                    …{
                        string strsql=SQLStringList[n].ToString();
                        if (strsql.Trim().Length>1)
                        …{
                            cmd.CommandText=strsql;
                            cmd.ExecuteNonQuery();
                        }
                    }                                       
                    tx.Commit();                   
                }
                catch(System.Data.OleDb.OleDbException E)
                …{       
                    tx.Rollback();
                    throw new Exception(E.Message);
                }
            }
        }
        /**//// <summary>
        /// 执行带一个存储过程参数的的SQL语句。
        /// </summary>
        /// <param name=”SQLString”>SQL语句</param>
        /// <param name=”content”>参数内容,比如一个字段是格式复杂的文章，有特殊符号，可以通过这个方式添加</param>
        /// <returns>影响的记录数</returns>
        public static int ExecuteSql(string SQLString,string content)
        …{               
            using (OleDbConnection connection = new OleDbConnection(connectionString))
            …{
                OleDbCommand cmd = new OleDbCommand(SQLString,connection);       
                System.Data.OleDb.OleDbParameter  myParameter = new System.Data.OleDb.OleDbParameter( “@content”,OleDbType.VarChar);
                myParameter.Value = content ;
                cmd.Parameters.Add(myParameter);
                try
                …{
                    connection.Open();
                    int rows=cmd.ExecuteNonQuery();
                    return rows;
                }
                catch(System.Data.OleDb.OleDbException E)
                …{               
                    throw new Exception(E.Message);
                }
                finally
                …{
                    cmd.Dispose();
                    connection.Close();
                }   
            }
        }       
       
        /**//// <summary>
        /// 执行一条计算查询结果语句，返回查询结果（object）。
        /// </summary>
        /// <param name=”SQLString”>计算查询结果语句</param>
        /// <returns>查询结果（object）</returns>
        public static object GetSingle(string SQLString)
        …{
            using (OleDbConnection connection = new OleDbConnection(connectionString))
            …{
                using(OleDbCommand cmd = new OleDbCommand(SQLString,connection))
                …{
                    try
                    …{
                        connection.Open();
                        object obj = cmd.ExecuteScalar();
                        if((Object.Equals(obj,null))||(Object.Equals(obj,System.DBNull.Value)))
                        …{                   
                            return null;
                        }
                        else
                        …{
                            return obj;
                        }               
                    }
                    catch(System.Data.OleDb.OleDbException e)
                    …{                       
                        connection.Close();
                        throw new Exception(e.Message);
                    }   
                }
            }
        }
        /**//// <summary>
        /// 执行查询语句，返回SqlDataReader
        /// </summary>
        /// <param name=”strSQL”>查询语句</param>
        /// <returns>SqlDataReader</returns>
        public static OleDbDataReader ExecuteReader(string strSQL)
        …{
            OleDbConnection connection = new OleDbConnection(connectionString);           
            OleDbCommand cmd = new OleDbCommand(strSQL,connection);               
            try
            …{
                connection.Open();   
                OleDbDataReader myReader = cmd.ExecuteReader();
                return myReader;
            }
            catch(System.Data.OleDb.OleDbException e)
            …{                               
                throw new Exception(e.Message);
            }           
           
        }       
        /**//// <summary>
        /// 执行查询语句，返回DataSet
        /// </summary>
        /// <param name=”SQLString”>查询语句</param>
        /// <returns>DataSet</returns>
        public static DataSet Query(string SQLString)
        …{
            using (OleDbConnection connection = new OleDbConnection(connectionString))
            …{
                DataSet ds = new DataSet();
                try
                …{
                    connection.Open();
                    OleDbDataAdapter command = new OleDbDataAdapter(SQLString,connection);               
                    command.Fill(ds,”ds”);
                }
                catch(System.Data.OleDb.OleDbException ex)
                …{               
                    throw new Exception(ex.Message);
                }           
                return ds;
            }           
        }

    }