Using SqlCommand objects in code

4.1 Used in code SqlCommand object

4.1.1 establish sqlCommand object

// Create without parameters

sqlCommand cmd;

cmd = new sqlCommand();

cmd.Connection = cn;

cmd.CommandText = strSQL;

// Use parameters to construct

sqlCommand cmd = new sqlCommand( strSQL.cn);

// use connection Of CreateCommand To construct the

cmd = cn.CreateCommand();

cmd.CommandText = strSQL;

4.1.3 Execute the query that returns rows

sqlCommand cmd = cn.CreateCommand();

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

SqlDataReader dr = cmd.ExecuteReader();

while(dr.Read())

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

4.1.4 Get a single value

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

sqlCommandText = new sqlCommand(strSQL,cn);

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

4.1.5 Execute queries that do not return result sets

strSQL ="Update table set field01=100"

sqlCommand cmd = new sqlCommand(strSQL,cn);

int iRow= cmd.ExecuteNonQuery(); // The return value is the number of rows affected , Reflect the successful implementation

4.1.6 Execute batch operation query

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();// Return the total number of rows modified by each query ,

utilize StatementCompleted Event can determine the number of rows modified by each query in batch operation

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;// The number of rows affected by each query can be reflected here

}