C# ADO.NET 数据库连接的管理类

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

namespace SQLServerAccess
{
    /// <summary>
    /// 数据库连接管理类（SQLServer）
    /// <!-- 注意：使用该类需要在配置文件中加入以下配置 -->
    /// <!-- 数据库：连接字符串 -->
    /// <add key="DbConnectionString" value="Data Source=地址;Initial Catalog=数据库名称;Persist Security Info=True;User ID=用户名;Password=密码;" />
    /// <!-- 数据库：连接超时设置（秒） -->
    /// <add key="DbConnectionTimeout" value="10" />
    /// <!-- 数据库：SQL执行超时设置（秒） -->
    /// <add key="DbCommandTimeout" value="30" />
    /// </summary>
    public class DbConnection : IDisposable
    {
        /// <summary>
        /// 保持与数据库的连接
        /// </summary>
        private SqlConnection innerConnection = new SqlConnection();

        /// <summary>
        /// 事务对象
        /// </summary>
        private SqlTransaction innerTransaction;

        /// <summary>
        /// SQL命令对象
        /// </summary>
        private SqlCommand innerCommand;

        /// <summary>
        /// 获得连接
        /// </summary>
        public SqlConnection Connection
        {
            get { return this.innerConnection; }
        }

        /// <summary>
        /// 返回一个命令
        /// </summary>
        public SqlCommand Command
        {
            get { return this.innerCommand; }
        }

        /// <summary>
        /// 检索数据库的事务是否正在启动
        /// </summary>
        public bool IsTransaction
        {
            get
            {
                bool ret = false;
                if (this.innerTransaction != null)
                {
                    ret = (this.innerTransaction.Connection != null);
                }
                return ret;
            }
        }

        /// <summary>
        /// 创建数据库的连接对象并打开连接
        /// </summary>
        public void Open(string DBConnectionString = null)
        {
            if (string.IsNullOrEmpty(DBConnectionString))
            {
                // 默认的数据库
                DBConnectionString = ConfigurationManager.AppSettings["DBConnectionString"];
            }
            // 数据库连接超时时间
            int DbConnectionTimeout = 10;
            if (!string.IsNullOrEmpty(ConfigurationManager.AppSettings["DbConnectionTimeout"]))
            {
                DbConnectionTimeout = int.Parse(ConfigurationManager.AppSettings["DbConnectionTimeout"]);
            }
            // SQL执行超时时间
            int DbCommandTimeout = 30;
            if (!string.IsNullOrEmpty(ConfigurationManager.AppSettings["DbCommandTimeout"]))
            {
                DbCommandTimeout = int.Parse(ConfigurationManager.AppSettings["DbCommandTimeout"]);
            }

            // 如果连接已打开，则表示错误
            if (this.innerConnection.State != ConnectionState.Broken &&
                this.innerConnection.State != ConnectionState.Closed)
            {
                //错误处理
                throw new Exception("DBOpen Error.");
            }

            try
            {
                // 连接字符串设置
                innerConnection.ConnectionString = DBConnectionString + ";Connection Timeout=" + DbConnectionTimeout;
                // 打开连接
                innerConnection.Open();
                // 命令
                innerCommand = innerConnection.CreateCommand();
                innerCommand.CommandTimeout = DbCommandTimeout;
            }
            catch (Exception ex)
            {
                if (innerTransaction != null) innerTransaction.Dispose();
                if (innerCommand != null) innerCommand.Dispose();
                if (innerConnection != null) innerConnection.Dispose();
                throw ex;
            }
        }

        /// <summary>
        /// 关闭与用户数据库的连接
        /// </summary>
        public void Close()
        {
            if (this.innerConnection != null &&
                this.innerTransaction != null &&
                this.innerTransaction.Connection != null)
            {
                try
                {
                    this.innerTransaction.Rollback();
                }
                catch (Exception)
                {
                }
                finally
                {
                    this.innerTransaction = null;
                }
            }

            try
            {
                this.innerConnection.Close();
                this.innerConnection.Dispose();
                this.innerTransaction = null;
            }
            catch (Exception)
            {
            }
            finally
            {
                this.innerConnection = new SqlConnection();
            }
        }

        /// <summary>
        /// 事务开始
        /// </summary>
        public void BeginTran()
        {
            if (this.innerTransaction != null)
            {
                // 该事务已经开始
                return;
            }

            try
            {
                // 开始事务
                innerTransaction = innerConnection.BeginTransaction();
                innerCommand.Transaction = innerTransaction;
            }
            catch (Exception ex)
            {
                throw ex;

            }
        }

        /// <summary>
        /// 事务提交
        /// </summary>
        public void Commit()
        {
            if (this.innerTransaction == null)
            {
                // 事务未开始
                return;
            }

            try
            {
                this.innerTransaction.Commit();
                this.innerTransaction = null;
            }
            catch (SqlException sqlex)
            {
                throw sqlex;
            }
            finally
            {
                if (this.innerTransaction != null &&
                    this.innerTransaction.Connection != null)
                {
                    try
                    {
                        this.innerTransaction.Rollback();
                        this.innerTransaction = null;
                    }
                    catch (Exception) { }
                }
            }
        }

        /// <summary>
        /// 事务回滚
        /// </summary>
        public void Rollback()
        {
            if (this.innerTransaction == null)
            {
                // 事务未开始
                return;
            }

            try
            {
                this.innerTransaction.Rollback();
                this.innerTransaction = null;
            }
            catch (SqlException sqlex)
            {
                throw sqlex;
            }
        }

        /// <summary>
        /// 构造函数
        /// </summary>
        public DbConnection(string DBConnectionString = null, bool openFlag = true)
        {
            if (openFlag)
            {
                Open(DBConnectionString);
            }
        }

        /// <summary>
        /// 释放资源
        /// </summary>
        public void Dispose()
        {
            Close();
        }
    }
}