using System.Data;
    using System.Data.Common;
    using System.Configuration;

    public class DbHelper
    {
        private static string dbProviderName = ConfigurationManager.AppSettings["DbHelperProvider"];
        private static string dbConnectionString = ConfigurationManager.AppSettings["DbHelperConnectionString"];

        private DbConnection connection;
        public DbHelper()
        {
            this.connection = CreateConnection(DbHelper.dbConnectionString);
        }
        public DbHelper(string connectionString)
        {
            this.connection = CreateConnection(connectionString);
        }
        public static DbConnection CreateConnection()
        {
            DbProviderFactory dbfactory = DbProviderFactories.GetFactory(DbHelper.dbProviderName);
            DbConnection dbconn = dbfactory.CreateConnection();
            dbconn.ConnectionString = DbHelper.dbConnectionString;
            return dbconn;
        }
        public static DbConnection CreateConnection(string connectionString)
        {
            DbProviderFactory dbfactory = DbProviderFactories.GetFactory(DbHelper.dbProviderName);
            DbConnection dbconn = dbfactory.CreateConnection();
            dbconn.ConnectionString = connectionString;
            return dbconn;
        }

        public DbCommand GetStoredProcCommond(string storedProcedure)
        {
            DbCommand dbCommand = connection.CreateCommand();
            dbCommand.CommandText = storedProcedure;
            dbCommand.CommandType = CommandType.StoredProcedure;
            return dbCommand;
        }
        public DbCommand GetSqlStringCommond(string sqlQuery)
        {
            DbCommand dbCommand = connection.CreateCommand();
            dbCommand.CommandText = sqlQuery;
            dbCommand.CommandType = CommandType.Text;
            return dbCommand;
        }

        增加参数#region 增加参数
        public void AddParameterCollection(DbCommand cmd, DbParameterCollection dbParameterCollection)
        {
            foreach (DbParameter dbParameter in dbParameterCollection)
            {
                cmd.Parameters.Add(dbParameter);
            }
        }
        public void AddOutParameter(DbCommand cmd, string parameterName, DbType dbType, int size)
        {
            DbParameter dbParameter = cmd.CreateParameter();
            dbParameter.DbType = dbType;
            dbParameter.ParameterName = parameterName;
            dbParameter.Size = size;
            dbParameter.Direction = ParameterDirection.Output;
            cmd.Parameters.Add(dbParameter);
        }
        public void AddInParameter(DbCommand cmd, string parameterName, DbType dbType, object value)
        {
            DbParameter dbParameter = cmd.CreateParameter();
            dbParameter.DbType = dbType;
            dbParameter.ParameterName = parameterName;
            dbParameter.Value = value;
            dbParameter.Direction = ParameterDirection.Input;
            cmd.Parameters.Add(dbParameter);
        }
        public void AddReturnParameter(DbCommand cmd, string parameterName, DbType dbType)
        {
            DbParameter dbParameter = cmd.CreateParameter();
            dbParameter.DbType = dbType;
            dbParameter.ParameterName = parameterName;
            dbParameter.Direction = ParameterDirection.ReturnValue;
            cmd.Parameters.Add(dbParameter);
        }
        public DbParameter GetParameter(DbCommand cmd, string parameterName)
        {
            return cmd.Parameters[parameterName];
        }

        #endregion

        执行#region 执行
        public DataSet ExecuteDataSet(DbCommand cmd)
        {
            DbProviderFactory dbfactory = DbProviderFactories.GetFactory(DbHelper.dbProviderName);
            DbDataAdapter dbDataAdapter = dbfactory.CreateDataAdapter();
            dbDataAdapter.SelectCommand = cmd;
            DataSet ds = new DataSet();
            dbDataAdapter.Fill(ds);
            return ds;
        }

        public DataTable ExecuteDataTable(DbCommand cmd)
        {
            DbProviderFactory dbfactory = DbProviderFactories.GetFactory(DbHelper.dbProviderName);
            DbDataAdapter dbDataAdapter = dbfactory.CreateDataAdapter();
            dbDataAdapter.SelectCommand = cmd;
            DataTable dataTable = new DataTable();
            dbDataAdapter.Fill(dataTable);
            return dataTable;
        }

        public DbDataReader ExecuteReader(DbCommand cmd)
        {
            cmd.Connection.Open();
            DbDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);           
            return reader;
        }
        public int ExecuteNonQuery(DbCommand cmd)
        {
            cmd.Connection.Open();
            int ret = cmd.ExecuteNonQuery();
            cmd.Connection.Close();
            return ret;
        }

        public object ExecuteScalar(DbCommand cmd)
        {
            cmd.Connection.Open();
            object ret = cmd.ExecuteScalar();
            cmd.Connection.Close();
            return ret;
        }
        #endregion       

        执行事务#region 执行事务
        public DataSet ExecuteDataSet(DbCommand cmd,Trans t)
        {
            cmd.Connection = t.DbConnection;
            cmd.Transaction = t.DbTrans;
            DbProviderFactory dbfactory = DbProviderFactories.GetFactory(DbHelper.dbProviderName);
            DbDataAdapter dbDataAdapter = dbfactory.CreateDataAdapter();
            dbDataAdapter.SelectCommand = cmd;
            DataSet ds = new DataSet();
            dbDataAdapter.Fill(ds);
            return ds;
        }

        public DataTable ExecuteDataTable(DbCommand cmd, Trans t)
        {
            cmd.Connection = t.DbConnection;
            cmd.Transaction = t.DbTrans;
            DbProviderFactory dbfactory = DbProviderFactories.GetFactory(DbHelper.dbProviderName);
            DbDataAdapter dbDataAdapter = dbfactory.CreateDataAdapter();
            dbDataAdapter.SelectCommand = cmd;
            DataTable dataTable = new DataTable();
            dbDataAdapter.Fill(dataTable);
            return dataTable;
        }

        public DbDataReader ExecuteReader(DbCommand cmd, Trans t)
        {
            cmd.Connection.Close();
            cmd.Connection = t.DbConnection;
            cmd.Transaction = t.DbTrans;           
            DbDataReader reader = cmd.ExecuteReader();
            DataTable dt = new DataTable();           
            return reader;
        }
        public int ExecuteNonQuery(DbCommand cmd, Trans t)
        {
            cmd.Connection.Close();
            cmd.Connection = t.DbConnection;
            cmd.Transaction = t.DbTrans;
            int ret = cmd.ExecuteNonQuery();           
            return ret;
        }

        public object ExecuteScalar(DbCommand cmd, Trans t)
        {
            cmd.Connection.Close();
            cmd.Connection = t.DbConnection;
            cmd.Transaction = t.DbTrans;
            object ret = cmd.ExecuteScalar();           
            return ret;
        }
        #endregion
    }

    public class Trans : IDisposable
    {
        private DbConnection conn;
        private DbTransaction dbTrans;
        public DbConnection DbConnection
        {
            get { return this.conn; }
        }
        public DbTransaction DbTrans
        {
            get { return this.dbTrans; }
        }

        public Trans()
        {
            conn = DbHelper.CreateConnection();
            conn.Open();
            dbTrans = conn.BeginTransaction();
        }
        public Trans(string connectionString)
        {
            conn = DbHelper.CreateConnection(connectionString);
            conn.Open();
            dbTrans = conn.BeginTransaction();
        }
        public void Commit()
        {
            dbTrans.Commit();
            this.Colse();
        }

        public void RollBack()
        {
            dbTrans.Rollback();
            this.Colse();
        }

        public void Dispose()
        {
            this.Colse();
        }

        public void Colse()
        {
            if (conn.State == System.Data.ConnectionState.Open)
            {
                conn.Close();
            }
        }
    }
那么如何使用它呢?下面我给出一些基本的使用示例,基本能满足你大部分的数据库操作需要了.
1)直接执行sql语句

        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetSqlStringCommond("insert t1 (id)values('haha')");
        db.ExecuteNonQuery(cmd);
2)执行存储过程

        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetStoredProcCommond("t1_insert");
        db.AddInParameter(cmd, "@id", DbType.String, "heihei");
        db.ExecuteNonQuery(cmd);
3)返回DataSet

        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetSqlStringCommond("select * from t1");
        DataSet ds = db.ExecuteDataSet(cmd);
4)返回DataTable

        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetSqlStringCommond("t1_findall");
        DataTable dt = db.ExecuteDataTable(cmd);
5)输入参数/输出参数/返回值的使用(比较重要哦)

        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetStoredProcCommond("t2_insert");
        db.AddInParameter(cmd, "@timeticks", DbType.Int64, DateTime.Now.Ticks);
        db.AddOutParameter(cmd, "@outString", DbType.String, 20);
        db.AddReturnParameter(cmd, "@returnValue", DbType.Int32);

        db.ExecuteNonQuery(cmd);

        string s = db.GetParameter(cmd, "@outString").Value as string;//out parameter
        int r = Convert.ToInt32(db.GetParameter(cmd, "@returnValue").Value);//return value

6)DataReader使用

      DbHelper db = new DbHelper();
        DbCommand cmd = db.GetStoredProcCommond("t2_insert");
        db.AddInParameter(cmd, "@timeticks", DbType.Int64, DateTime.Now.Ticks);
        db.AddOutParameter(cmd, "@outString", DbType.String, 20);
        db.AddReturnParameter(cmd, "@returnValue", DbType.Int32);

        using (DbDataReader reader = db.ExecuteReader(cmd))
        {
            dt.Load(reader);
        }       
        string s = db.GetParameter(cmd, "@outString").Value as string;//out parameter
        int r = Convert.ToInt32(db.GetParameter(cmd, "@returnValue").Value);//return value

7)事务的使用.(项目中需要将基本的数据库操作组合成一个完整的业务流时,代码级的事务是必不可少的哦)
    pubic void DoBusiness()
    {
        using (Trans t = new Trans())
        {
            try
            {
                D1(t);
                throw new Exception();//如果有异常,会回滚滴
                D2(t);
                t.Commit();
            }
            catch
            {
                t.RollBack();
            }
        }
    }
    public void D1(Trans t)
    {
        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetStoredProcCommond("t2_insert");
        db.AddInParameter(cmd, "@timeticks", DbType.Int64, DateTime.Now.Ticks);
        db.AddOutParameter(cmd, "@outString", DbType.String, 20);
        db.AddReturnParameter(cmd, "@returnValue", DbType.Int32);

        if (t == null) db.ExecuteNonQuery(cmd);
        else db.ExecuteNonQuery(cmd,t);

        string s = db.GetParameter(cmd, "@outString").Value as string;//out parameter
        int r = Convert.ToInt32(db.GetParameter(cmd, "@returnValue").Value);//return value
    }
    public void D2(Trans t)
    {
        DbHelper db = new DbHelper();
        DbCommand cmd = db.GetSqlStringCommond("insert t1 (id)values('..')");       
        if (t == null) db.ExecuteNonQuery(cmd);
        else db.ExecuteNonQuery(cmd, t);
    }
以上我们好像没有指定数据库连接字符串,大家如果看下DbHelper的代码,就知道要使用它必须在config中配置两个参数,如下:
    <appSettings>
        <add key="DbHelperProvider" value="System.Data.SqlClient"/>
        <add key="DbHelperConnectionString" value="Data Source=(local);Initial Catalog=DbHelperTest;Persist Security Info=True;User ID=sa;Password=sa"/>
    </appSettings>其实,DbHelper需要的仅仅是两个字符串,你可以自己修改,作成加密什么的...