ADO.NET之sqlCommand对象

4.1在代码中使用SqlCommand对象

4.1.1创建sqlCommand对象

//不使用参数创建

sqlCommand cmd;

cmd = new sqlCommand();

cmd.Connection = cn;

cmd.CommandText = strSQL;

//使用参数来构造

sqlCommand cmd = new sqlCommand( strSQL.cn);

//用connection的CreateCommand来构造

cmd = cn.CreateCommand();

cmd.CommandText = strSQL;

4.1.3 执行返回行的查询

sqlCommand cmd = cn.CreateCommand();

cmd.CommandText = "select * From ...";

SqlDataReader dr = cmd.ExecuteReader();

while(dr.Read())

Console.Write(dr["UserName"]);

4.1.4 获取单一值

strSQL = "select count(*) from tabname";

sqlCommandText = new sqlCommand(strSQL,cn);

int icount  = (int)cmd.ExecuteScalar();

4.1.5执行不返回结果集的查询

strSQL ="Update table set field01=100"

sqlCommand cmd = new sqlCommand(strSQL,cn);

int iRow= cmd.ExecuteNonQuery(); //返回值是受影响的行数，反应执行成功的情况

4.1.6 执行批量操作查询

strSQL ="update table01 set field01 =001 .." +

                "update table02 set field01 =002 .." +

                "update table03 set field01 =003 .."

sqlCommand cmd = new sqlCommand(strSQL,cn);

int icount = cmd.ExecuteNonQuery();//返回各个查询所修改的总行数,

利用StatementCompleted事件可以确定批量操作中各个查询所修改的行数

sqlCommand cmd = new sqlCommand(strSQL,cn);

cmd.StatementCompleted += new StatementCompletedEventHandler(HandleStatementCompleted);

int irow = cmd.ExcuteNonQuery();

static void HandleStatementCompleted(object sender,StatementCompletedEventArgs e)

{

    int row = e.RecordCount;//这里能反应出每个查询受影响的行数

}