多数据之间的连接操作-MSSQL(不完整)

using System;
using System.Data;
using System.Data.SqlClient;

namespace ASPNETClassLibrary
...{
    /**//// <summary>
    /// Command_SQL 的摘要说明。
    /// </summary>
    public class Command_SQL
    ...{
        public Command_SQL()
        ...{
        }
        
        ...#region

        /**//// <summary>
        /// 连接数据字段
        /// </summary>
        private static string _connectionString;
        /**//// <summary>
        /// 设置为只读
        /// </summary>
        public static  string connectionString
        ...{
            get
            ...{
                return _connectionString ;
            }
            set
            ...{
                _connectionString = value;
            }
        }


        /**//// <summary>
        /// 打开数据的连接
        /// </summary>
        /// <returns></returns>
        public static SqlConnection getSqlConnection()
        ...{
            try
            ...{
                string SqlString = _connectionString ; //"Provider=Microsoft.Jet.Sql.4.0;User ID=Admin;Data Source='" + HttpContext.Current.Server.MapPath("~/LHB_DataBase/LHB.mdb") + "';Jet Sql:Engine Type=5;Jet Sql:Database Locking Mode=1;Jet Sql:Global Partial Bulk Ops=2;Jet Sql:Global Bulk Transactions=1;Jet Sql:Create System Database=False;Jet Sql:Encrypt Database=False;Jet Sql:Don't Copy Locale on Compact=False;Jet Sql:Compact Without Replica Repair=False;Jet Sql:SFP=False";
                SqlConnection oc = new SqlConnection(SqlString);
                oc.Open();
                return oc;
            }
            catch(Exception ex)
            ...{
                string temp = ex.Message;
                return null;
            }
        }
    

        /**//// <summary>
        /// 获取 SqlCommand 对象
        /// </summary>
        /// <returns></returns>
        public static SqlCommand getSqlCommand()
        ...{
            SqlConnection cn =  getSqlConnection();
            if (cn == null)
            ...{
                return null;
            }
            else
            ...{
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = cn;
                return cmd;
            }
        }


        /**//// <summary>
        /// 新建一个DataSet对象
        /// </summary>
        /// <param name="ExecuteString">要执行的语句,可是Sql语句,也可是存储过程的名称</param>
        /// <returns></returns>
        public static DataSet getDataSet(string ExecuteString)
        ...{
            SqlConnection cn =  getSqlConnection();
            SqlDataAdapter odda = new SqlDataAdapter(ExecuteString,cn);
            DataSet ds = new DataSet();
            if (cn == null)
            ...{
                return null;
            }
            else
            ...{
                odda.Fill(ds);
                return ds;
            }
        }


        /**//// <summary>
        /// 新建一个DataSet对象
        /// </summary>
        /// <param name="ExecuteString">要执行的语句,可是Sql语句,也可是存储过程的名称</param>
        /// <param name="name">表的名字</param>
        /// <returns></returns>
        public static DataSet getDataSet(string ExecuteString, string name)
        ...{
            SqlConnection cn =  getSqlConnection();
            SqlDataAdapter odda = new SqlDataAdapter(ExecuteString,cn);
            DataSet ds = new DataSet();
            if (cn == null)
            ...{
                return null;
            }
            else
            ...{
                odda.Fill(ds,name);
                return ds;
            }

        }

    
        /**//// <summary>
        /// 新建一个DataSet对象
        /// </summary>
        /// <param name="ExecuteString">要执行的语句,可是Sql语句,也可是存储过程的名称</param>
        /// <returns></returns>
        public static DataTable getDataTable(string ExecuteString)
        ...{
            SqlConnection cn =  getSqlConnection();
            SqlDataAdapter odda = new SqlDataAdapter(ExecuteString,cn);
            DataTable dt = new DataTable();
            if (cn == null)
            ...{
                return null;
            }
            else
            ...{
                odda.Fill(dt);
                return dt;
            }

        }


        /**//// <summary>
        /// 执行SQL语句,返回受影响的行数，
        /// -2 说明数据连接失败，
        /// -3 发生异常错误。
        /// </summary>
        /// <param name="ExecuteString">要执行的语句,可是Sql语句,也可是存储过程的名称</param>
        /// <returns></returns>
        public static int ExecuteNonQuery(string ExecuteString)
        ...{
            int count;
            SqlCommand cmd =  getSqlCommand();
            if (cmd == null)
            ...{
                /**//// <summary>
                /// 说明数据连接失败
                /// <summary> 
                return -2;
            }
            else
            ...{
                /**//// <summary>
                /// 把要执行的字符串给LHB_CMD
                /// <summary> 
                cmd.CommandText = ExecuteString;
                /**//// <summary>
                /// 开始执行
                /// <summary> 
                count = cmd.ExecuteNonQuery();
                /**//// <summary>
                /// 返回一个值.
                /// <summary>        
                return count;
            }
        }

        
        /**//// <summary>
        /// 执行指定的Sql语句，返回首行首列
        ///  -2 说明数据连接失败，
        ///  -3 发生异常错误。
        /// </summary>
        /// <param name="ExecuteString">要执行的语句,可是Sql语句,也可是存储过程的名称</param>
        /// <returns>返回首行首列的那个值</returns>
        public static string ExecuteScalar(string ExecuteString)
        ...{
            try
            ...{
                string ShouHangShouLie;
                SqlCommand cmd =  getSqlCommand();
                if (cmd == null)
                ...{
                    return "-2";
                }
                else
                ...{
                    cmd.CommandText = ExecuteString;
                    ShouHangShouLie = cmd.ExecuteScalar().ToString();
                    return ShouHangShouLie;
                }
            }
            catch (Exception LHB_EE)
            ...{
                string temp = LHB_EE.Message;
                return "-3";
            }
        }

    
        #endregion
    }
}