参照别人的方法，顺便再次复习下ADO.NET的相关知识。为自己的类库做准备。

namespace Common.SqlHelper
{/// <summary>/// ADO.NET-------底层的数据操作/// </summary>public class SqlHelper{/// <summary>/// 通过构造函数来实例化连接字符串/// </summary>/// <param name="connectionString"></param>public SqlHelper(string connectionString){this.connectionString = connectionString;}private string connectionString;/// <summary>/// 设置DB访问字符串/// </summary>public string ConnectionSrting{set { connectionString = value; }}#region 执行一个查询，返回查询的结果集+ExecuteDataTable(string sql, CommandType commandtype, SqlParameter[] parameters)public DataTable ExecuteDataTable(string sql){return ExecuteDataTable(sql, CommandType.Text, null);}public DataTable ExecuteDataTable(string sql, CommandType commandType){return ExecuteDataTable(sql, commandType, null);}/// <summary>/// 执行一个查询，返回查询的结果集。/// </summary>/// <param name="sql"></param>/// <param name="commandtype"></param>/// <param name="parameters"></param>/// <returns></returns>public DataTable ExecuteDataTable(string sql, CommandType commandtype, SqlParameter[] parameters){DataTable data = new DataTable();  //实例化datatable,用于装载查询的结果集using (SqlConnection conn = new SqlConnection(connectionString)){using (SqlCommand cmd = new SqlCommand(sql, conn)){cmd.CommandType = commandtype;if (parameters != null){foreach (SqlParameter parameter in parameters){cmd.Parameters.Add(parameter);   //将参数添加到sql语句中。}}//申明sqldataadapter，通过cmd来实例化它，这个是数据设备器，可以直接往datatable,dataset中写入。SqlDataAdapter adapter = new SqlDataAdapter(cmd);adapter.Fill(data);   //利用Fill来填充。}}return data;}#endregion#region 返回一个SqlDataReader对象。public SqlDataReader ExecuteReader(string sql){return ExecuteReader(sql, CommandType.Text, null);}public SqlDataReader ExecuteReader(string sql, CommandType commandType){return ExecuteReader(sql, commandType, null);}/// <summary>/// 返回一个SqlDataReader，从 SQL Server 数据库读取行的只进流的方式/// </summary>/// <returns></returns>public SqlDataReader ExecuteReader(string sql, CommandType commandType, SqlParameter[] parameters){SqlConnection conn = new SqlConnection(connectionString);SqlCommand cmd = new SqlCommand(sql, conn);if (parameters != null){foreach (SqlParameter parameter in parameters){cmd.Parameters.Add(parameter);}}conn.Open();//CommandBehavior.CloseConnection+关闭reader对象关闭与其连接的Connection对象。return cmd.ExecuteReader(CommandBehavior.CloseConnection);}#endregion#region 执行一个查询，返回结果集的首行首列。忽略其他行，其他列/// <summary>/// 只执行sql语句/// </summary>/// <param name="sql"></param>/// <returns></returns>public object ExecuteScalar(string sql){return ExecuteScalar(sql, CommandType.Text, null);}/// <summary>/// 可以执行存储过程/// </summary>/// <param name="sql"></param>/// <param name="commandType"></param>/// <returns></returns>public object ExecuteScalar(string sql, CommandType commandType){return ExecuteScalar(sql, commandType, null);}/// <summary>/// 执行一个查询，返回结果集的首行首列/// </summary>/// <param name="sql"></param>/// <param name="commandType"></param>/// <param name="parameters"></param>/// <returns></returns>public object ExecuteScalar(string sql, CommandType commandType, SqlParameter[] parameters){SqlConnection conn = new SqlConnection(connectionString);SqlCommand cmd = new SqlCommand(sql, conn);cmd.CommandType = commandType;if (parameters != null){foreach (SqlParameter parameter in parameters){cmd.Parameters.Add(parameter);}}conn.Open();//cmd.ExecuteScalar()+执行查询，并返回查询所返回的结果集中第一行的第一列。 忽略其他列或行。object result = cmd.ExecuteScalar();conn.Close();return result;}#endregion#region 进行CRUD操作public int ExecuteNonQuery(string sql){return ExecuteNonQuery(sql,CommandType.Text,null);}public int ExecuteNonQuery(string sql,CommandType commandType){return ExecuteNonQuery(sql, commandType, null);}/// <summary>/// 对数据库进行增删改的操作/// </summary>/// <param name="sql">执行的Sql语句</param>/// <param name="commandType">要执行的查询语句类型，如存储过程或者sql文本命令</param>/// <param name="parameters">Transact-SQL语句或者存储过程的参数数组</param>/// <returns></returns>public int ExecuteNonQuery(string sql,CommandType commandType,SqlParameter[]parameters){SqlConnection conn=new SqlConnection(connectionString);SqlCommand cmd=new SqlCommand(sql,conn);cmd.CommandType = commandType;if (parameters!=null){foreach (SqlParameter parameter in parameters){cmd.Parameters.Add(cmd);}}conn.Open();int count = cmd.ExecuteNonQuery();conn.Close();return count;}#endregion#region  返回当前连接的数据库中所有用户创建的数据库/// <summary>/// 返回当前连接的数据库中所有用户创建的数据库/// </summary>        /// <param name="tableName">表名</param>/// <returns></returns>public DataTable GetTable(string tableName){DataTable table = new DataTable();using (SqlConnection conn = new SqlConnection(connectionString)){conn.Open();table = conn.GetSchema(tableName);}return table;} #endregion}
}