封装的DBHelper（C#）

  <!--连接数据库字符串-->
  <connectionStrings>
    <add name="DBStrConn" connectionString="Data Source=.; initial Catalog=数据库; user id=用户名; password=密码"/>
  </connectionStrings>

/*
 * 获取连接数据库字符串
 * 此字符串存在App.config应用配置文件中
*/
private static string strConnection = ConfigurationManager.ConnectionStrings["DBStrConn"].ConnectionString;　　//DBStrConn为在App.config中的"name"名

public static int ToInUpDel_ExecuteNonQuery(string sql)
{
    //连接命令
    using (SqlConnection conn = new SqlConnection(strConnection))
    {
       conn.Open();   //打开连接
       using (SqlCommand cmd = conn.CreateCommand())
       {
          //执行sql语句
          cmd.CommandText = sql;

          //返回受影响的行数
          return cmd.ExecuteNonQuery();

       }
    }
} 

public static int ToSelect_ExecuteScalar(string sql)
{
    using (SqlConnection conn = new SqlConnection(strConnection))
    {
        conn.Open();
        using (SqlCommand cmd = conn.CreateCommand())
        {
            cmd.CommandText = sql;
            //返回结果
            return (int)cmd.ExecuteScalar();
        }
    }
}

public static DataTable ExecuteDataTable(string sql)
{
       using (SqlConnection conn = new SqlConnection(strConnection))
       {
             conn.Open();
             using (SqlCommand cmd = conn.CreateCommand())
             {
                    cmd.CommandText = sql;
                    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                    DataSet dataset = new DataSet();
                    adapter.Fill(dataset);
                    return dataset.Tables[0];
             }
       }
 }       

public static SqlDataReader ExecuteReader(string sql)
{
    SqlConnection conn = new SqlConnection(strConnection);
    SqlCommand cmd = new SqlCommand(sql,conn);
    try
    {
	　　conn.Open();
	　　SqlDataReader reader = cmd.ExecuteReader(CommandBehavior.CloseConnection);　　//CommandBehavior.CloseConnection 在关闭DataReader的时候自动关闭Connection
	　　return reader;
    }
    catch(SqlException ex)
    {
	　　throw ex;
    } 
}