连接字符串

• server:表示连接的服务
• uid:sqlserver用户名
• pwd:密码
• database:表示要连接的数据库

cmd

• cmd.ExecutrScalar() 返回查询结果的第一行第一列的值

配置文件配置连接字符串

/* App.config */
<configuration>
  <connectionString>
    <add name="sql" connectionStrings="server=.;uid=sa;pwd=123456;database=demo"/>
  </connectionString>
</configuration>

//获得配置文件中的AppSetting中的数据
string connStr = ConfigurationManager.ConnectionStrings["sql"].ConnectionString;

DataSet和DataTable

// 创建一个内存的数据集
DataSet ds = new DataSet("DSS");
// 创建一张内存表
DataTable dt1 = new DataTable("dt1");
//把表放到数据集里面去
ds.Tables.Add(dt1);
// 给表定义列
DataColumn dcName = new DataColumn("Name",typeof(string));
// 把列放到表里面去
dt1.Colums.AddRange(new DataColumn[ ] {dcIName});
//给表添加数据
dt1.Rows.Add("陈莹");

SqlHelper封装

public class SqlHelper
{
    // 获取连接字符串
    public static string GetSqlConnectionString()
    {
        return ConfigurationManager.ConnectionStrings["sql"].ConnectionString;
    }

    // 封装一个执行sql返回受影响的行数
    public static int ExcuteNonQuery(string sqlText, params SqlParameter[] parameters)
    {
        using(GetSqlConnection conn = new GetSqlConnection(GetSqlConnectionString()))
        {
            using(SqlCommand cmd = conn.CreateCommand())
            {
                conn.Open();
                cmd.CommandText = sqlText;
                cmd.Parameters.AddRange(parameters);//参数添加到cmd命令中
                return cmd.ExecuteNonQuery();
            }
        }
    }

    //执行sql,返回查询结果中的第一行第一列的值
    public static object ExcuteScalar(string sqlText, params SqlParameter[] parameters)
    {
        using(GetSqlConnection conn = new GetSqlConnection(GetSqlConnectionString()))
        {
            using(SqlCommand cmd = conn.CreateCommand())
            {
                conn.Open();
                cmd.CommandText = sqlText;
                cmd.Parameters.AddRange(parameters);
                return cmd.ExcuteScalar();
            }
        }
    }

    //执行sql,返回一个DataTable
     public static DataTable ExcuteDataTable(string sqlText, params SqlParameter[] parameters)
     {
         using(SqlDataAdapter adapter = new SqlDataAdapter(sqlText, GetSqlConnectionString()))
         {
             DataTable dt = new DataTable();
             adapter.Fill(dt);
             return dt;
         }
     }

     //执行sql,返回一个SqlDataReader
     public static SqlDataReader ExcuteReader(string sqlText, params SqlParameter[] parameters)
     {
         //SqlDataReader要求,在在读取数据时,独占SqlConnection对象,SqlConnection必须是Open状态
         SqlConnection conn = new SqlConnection(GetSqlConnectionString());
         SqlCommand cmd = conn.CreateCommand();
         conn.Open();
         cmd.CommandText = sqlText;
         cmd.Parameters.AddRange(parameters);
         //当SqlDataReader释放时,把SqlConnection对象也释放掉
         return cmd.ExcuteReader(CommandBehavior.CloseConnection);
     }
}