連接字符串

• server:表示連接的服務(wù)
• uid:sqlserver用戶名
• pwd:密碼
• database:表示要連接的數(shù)據(jù)庫

cmd

• cmd.ExecutrScalar() 返回查詢結(jié)果的第一行第一列的值

配置文件配置連接字符串

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

//獲得配置文件中的AppSetting中的數(shù)據(jù)
string connStr = ConfigurationManager.ConnectionStrings["sql"].ConnectionString;

DataSet和DataTable

// 創(chuàng)建一個(gè)內(nèi)存的數(shù)據(jù)集
DataSet ds = new DataSet("DSS");
// 創(chuàng)建一張內(nèi)存表
DataTable dt1 = new DataTable("dt1");
//把表放到數(shù)據(jù)集里面去
ds.Tables.Add(dt1);
// 給表定義列
DataColumn dcName = new DataColumn("Name",typeof(string));
// 把列放到表里面去
dt1.Colums.AddRange(new DataColumn[ ] {dcIName});
//給表添加數(shù)據(jù)
dt1.Rows.Add("陳瑩");

SqlHelper封裝

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

    // 封裝一個(gè)執(zhí)行sql返回受影響的行數(shù)
    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);//參數(shù)添加到cmd命令中
                return cmd.ExecuteNonQuery();
            }
        }
    }

    //執(zhí)行sql,返回查詢結(jié)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();
            }
        }
    }

    //執(zhí)行sql,返回一個(gè)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;
         }
     }

     //執(zhí)行sql,返回一個(gè)SqlDataReader
     public static SqlDataReader ExcuteReader(string sqlText, params SqlParameter[] parameters)
     {
         //SqlDataReader要求,在在讀取數(shù)據(jù)時(shí),獨(dú)占SqlConnection對(duì)象,SqlConnection必須是Open狀態(tài)
         SqlConnection conn = new SqlConnection(GetSqlConnectionString());
         SqlCommand cmd = conn.CreateCommand();
         conn.Open();
         cmd.CommandText = sqlText;
         cmd.Parameters.AddRange(parameters);
         //當(dāng)SqlDataReader釋放時(shí),把SqlConnection對(duì)象也釋放掉
         return cmd.ExcuteReader(CommandBehavior.CloseConnection);
     }
}