SqlHelper数据库访问类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Data.SqlClient;
namespace CommDAL
{
    public class SqlHelper
    {

        private string sqlConnString;       // 数据库连接字符串
        private SqlConnection sqlConn = new SqlConnection();    // SQL数据库连接对象

        private ConnectionState sqlConnPreState = ConnectionState.Closed;   //原来数据库的连接状态

        /// <summary>
        /// 数据库连接字符串属性。
        /// </summary>
        public string SqlConnectionString
        {
            get
            {
                return sqlConnString;
            }
            set
            {
                sqlConnString = value;
                sqlConn.ConnectionString = sqlConnString;
            }
        }

        public SqlHelper()
        {

        }
        /// <summary>
        /// 构造函数。
        /// </summary>
        /// <param name="strSqlCon">数据库连接字符串。</param>
        public SqlHelper(string strSqlCon)
        {
            sqlConnString = strSqlCon;
            sqlConn.ConnectionString = sqlConnString;

        }

        /// <summary>
        /// 析构函数。
        /// </summary>
        ~SqlHelper()
        {
            try
            {
                Close();
                sqlConn.Dispose();
            }
            catch (Exception ex)
            {

                //throw ex;
                Console.Write(ex.Message);
            }

        }

        /// <summary>
        /// 打开数据库连接。
        /// </summary>
        public void Open()
        {
            try
            {
                if (sqlConn.State == ConnectionState.Closed)
                {
                    sqlConn.Open();
                    sqlConnPreState = ConnectionState.Open;
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }

        }

        /// <summary>
        /// 关闭数据库连接。
        /// </summary>
        public void Close()
        {
            try
            {
                if (sqlConn.State != ConnectionState.Closed)
                {
                    sqlConn.Close();
                    sqlConnPreState = ConnectionState.Closed;
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

        /// <summary>
        /// 获取查询的数据表。
        /// </summary>
        /// <param name="strSQL">要查询的SQL语句。</param>
        /// <param name="parametes">传入的参数，无参数时使用NULL。</param>
        /// <returns></returns>
        public DataTable GetDataTable(string strSQL, params SqlParameter[] parametes)
        {
            DataSet ds = new DataSet();
            DataTable dt = new DataTable();

            try
            {
                //sqlConn.Open();
                if (sqlConn.State == ConnectionState.Closed && sqlConn.State == ConnectionState.Closed)        //若原来的状态为关闭且当前连接未打开
                {
                    sqlConn.Open();
                }

                SqlCommand sqlCmd = sqlConn.CreateCommand();
                sqlCmd.CommandText = strSQL;

                if (parametes != null)
                {
                    sqlCmd.Parameters.Clear();
                    sqlCmd.Parameters.AddRange(parametes);
                }

                SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
                da.Fill(ds);
                dt = ds.Tables[0];
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (sqlConnPreState == ConnectionState.Closed && sqlConn.State != ConnectionState.Closed)  //若原来的状态为关闭且者当前连接未关闭则关闭
                {
                    sqlConn.Close();
                }
            }
            return dt;

        }

        /// <summary>
        /// 获取查询的数据集。
        /// </summary>
        /// <param name="strSQL">要查询的SQL语句。</param>
        /// <param name="parametes">传入的参数，无参数时使用NULL。</param>
        /// <returns></returns>
        public DataSet GetDataSet(string strSQL, params SqlParameter[] parametes)
        {
            DataSet ds = new DataSet();
            try
            {
                //sqlConn.Open();
                if (sqlConn.State == ConnectionState.Closed && sqlConn.State == ConnectionState.Closed)        //若原来的状态为关闭且当前连接未打开
                {
                    sqlConn.Open();
                }
                SqlCommand sqlCmd = sqlConn.CreateCommand();
                sqlCmd.CommandText = strSQL;

                if (parametes != null)
                {
                    sqlCmd.Parameters.Clear();
                    sqlCmd.Parameters.AddRange(parametes);
                }

                SqlDataAdapter da = new SqlDataAdapter(sqlCmd);
                da.Fill(ds);
                sqlConn.Close();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (sqlConnPreState == ConnectionState.Closed && sqlConn.State != ConnectionState.Closed)  //若原来的状态为关闭且者当前连接未关闭则关闭
                {
                    sqlConn.Close();
                }
            }
            return ds;
        }

        /// <summary>
        /// 返回SqlDataReader对象。该函数需要在外部打开和关闭连接操作。
        /// </summary>
        /// <param name="strSQL">传入的SQL语句。</param>
        /// <param name="parametes">传入的参数，无参数时使用NULL。</param>
        /// <returns></returns>
        public SqlDataReader ExecuteReader(string strSQL, params SqlParameter[] parametes)
        {
            SqlDataReader reader;
            try
            {
                if (sqlConn.State == ConnectionState.Closed && sqlConn.State == ConnectionState.Closed)        //若原来的状态为关闭且当前连接未打开
                {
                    sqlConn.Open();
                }
                //SqlCommand sqlCmd = sqlConn.CreateCommand();
                SqlCommand sqlCmd = sqlConn.CreateCommand();
             
                sqlCmd.CommandText = strSQL;

                if (parametes != null)
                {
                    sqlCmd.Parameters.Clear();
                    sqlCmd.Parameters.AddRange(parametes);
                }

                //reader = sqlCmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
                reader = sqlCmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            return reader;
        }

        /// <summary>
        /// 返回执行T-SQL语句受影响的行数。
        /// </summary>
        /// <param name="strSQL">执行的SQL语句。</param>
        /// <param name="parametes">传入的参数，无参数时使用NULL。</param>
        /// <returns></returns>
        public int ExecuteNonQuery(string strSQL, params SqlParameter[] parametes)
        {

            int sqlInt = -1;
            try
            {
                if (sqlConn.State == ConnectionState.Closed && sqlConn.State == ConnectionState.Closed)        //若原来的状态为关闭且当前连接未打开
                {
                    sqlConn.Open();
                }

                SqlCommand sqlCmd = sqlConn.CreateCommand();
                sqlCmd.CommandText = strSQL;

                if (parametes != null)
                {
                    sqlCmd.Parameters.Clear();
                    sqlCmd.Parameters.AddRange(parametes);
                }

                sqlInt = sqlCmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (sqlConnPreState == ConnectionState.Closed && sqlConn.State != ConnectionState.Closed)  //若原来的状态为关闭且者当前连接未关闭则关闭
                {
                    sqlConn.Close();
                }
            }
            return sqlInt;

        }

        /// <summary>
        /// 执行查询并返回第一行第一列的值。
        /// </summary>
        /// <param name="strSQL">执行的SQL语句。</param>
        /// <param name="parametes">传入的参数，无参数时使用NULL。</param>
        /// <returns></returns>
        public object ExecuteScalar(string strSQL, params SqlParameter[] parametes)
        {
            object obj;
            try
            {
                if (sqlConn.State == ConnectionState.Closed && sqlConn.State == ConnectionState.Closed)        //若原来的状态为关闭且当前连接未打开
                {
                    sqlConn.Open();
                }

                SqlCommand sqlCmd = sqlConn.CreateCommand();
                sqlCmd.CommandText = strSQL;

                if (parametes != null)
                {
                    sqlCmd.Parameters.Clear();
                    sqlCmd.Parameters.AddRange(parametes);
                }

                obj = sqlCmd.ExecuteScalar();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            //finally
            //{
            //    if (sqlConnPreState == ConnectionState.Closed && sqlConn.State != ConnectionState.Closed)  //若原来的状态为关闭且者当前连接未关闭则关闭
            //    {
            //        sqlConn.Close();
            //    }
            //}
            return obj;
        }

    }
}