C#自制数据库操作类代码

源代码如下：

using System;
using System.Data;
using System.Data.OleDb;
using System.IO;
using System.Windows.Forms;

namespace Test
{
    class Database
    {
        public static bool DataBase_Exists()
        {
            if (!File.Exists(Application.StartupPath + "\\DataBase.mdb"))
            {
                return false;
            }
            else
            {
                return true;
            }
        }

        public OleDbConnection Get_Conn()
        {
            try
            {
                string Conn_String = "";
                Conn_String = "Data Source='DataBase.mdb'; Provider=Microsoft.ACE.OLEDB.12.0;";
                OleDbConnection Db_Conn = new OleDbConnection(Conn_String);
                Db_Conn.Open();
                return Db_Conn;
            }
            catch (Exception e)
            {
                Error.Database_Error_Conn = e.Message.ToString();
                return null;
            }
        }

        public OleDbDataReader Select(string Select_String)
        {
            try
            {
                if (Get_Conn() == null)
                {
                    return null;
                }
                OleDbCommand Db_Cmd = new OleDbCommand(Select_String, Get_Conn());
                OleDbDataReader Db_Reader = Db_Cmd.ExecuteReader();
                Db_Reader.Read();
                return Db_Reader;
            }
            catch (Exception e)
            {
                Error.Database_Error_Select = e.Message.ToString();
                return null;
            }
        }

        public int Action_The_SQL(string SQL_String)
        {
            try
            {
                if (Get_Conn() == null)
                {
                    return 0;
                }
                OleDbCommand Db_Cmd = new OleDbCommand(SQL_String, Get_Conn());
                int Line = Db_Cmd.ExecuteNonQuery();
                return Line;
            }
            catch (Exception e)
            {
                Error.Database_Error_Action_The_SQL = e.Message.ToString();
                return 0;
            }
        }

        public DataSet GetDataSet(string SQL_String, string tableName)
        {
            try
            {
                if (Get_Conn() == null)
                {
                    return null;
                }
                OleDbDataAdapter Adapter = new OleDbDataAdapter(SQL_String, Get_Conn());
                DataSet DS = new DataSet();
                Adapter.Fill(DS, tableName);
                return DS;
            }
            catch (Exception j)
            {
                Error.Database_Error_GetDataSet = j.Message.ToString();
                return null;
            }
        }

        public string GetData(string SQL_String)
        {
            try
            {
                if (Get_Conn() == null)
                {
                    return null;
                }
                OleDbCommand Db_Cmd = new OleDbCommand(SQL_String, Get_Conn());
                string data = Convert.ToString(Db_Cmd.ExecuteScalar());
                return data;
            }
            catch (Exception e)
            {
                Error.Database_Error_Action_The_SQL = e.Message.ToString();
                return null;
            }
        }
    }
}

其引用的错误（Error）类源代码如下：

namespace Test{
    class Error
    {
        public static string Database_Error_Select;

        public static string Database_Error_Conn;

        public static string Database_Error_Action_The_SQL;

        public static string Database_Error_GetDataSet;
    }
}