CODEWITHSUNDEEP
c#sql.netmethodssqldatareader
Joshua Volearix
Joshua Volearix

Reputation: 313

Should I call SqlDataReader.HasRows if I am calling SqlReader.Read

Trying to see if it is beneficial to add an if (dr.HasRows) before the while (dr.read()) function. I mean, technically if it doesn't have rows it isn't going to read, so would it matter if you checked this first?

using (SqlDataReader dr = cmd.ExecuteReader())
{
    if (dr.HasRows)
    {
        while (dr.Read())
        {
            ....do stuff here
        }
    }
}

or is this going to essentially do the exact same thing if you're just making sure it has values to provide...

using (SqlDataReader dr = cmd.ExecuteReader())
{
    while (dr.Read())
    {
        ....do stuff here
    }
}

Upvotes: 24

Views: 54370

Answers (5)

adnan
adnan

Reputation: 1

try

            string myconnection = "datasource= localhost;port=3306;username=root;password=root;";
            MySqlConnection myconn = new MySqlConnection(myconnection);

            //MySqlDataAdapter mydata = new MySqlDataAdapter();
            MySqlDataReader myreader;

            MySqlCommand SelectCommand = new MySqlCommand("select *from student_info.student_info where username= '" + textBox1.Text +" 'and password=' " + textBox2.Text +"';",myconn );


            myconn.Open();

            myreader = SelectCommand.ExecuteReader();
            int count = 0;
            if (myreader.HasRows) //returing false but i have 4 row
            {
                while (myreader.Read()) //returing false 
                {
                    MessageBox.Show("in button3");
                    count = count + 1;
                }
            }

your opinion required

Upvotes: -4

Chalky
Chalky

Reputation: 1642

Be careful. HasRows() returns false for my CTE query, even though there are rows (437 rows actually).

Upvotes: 6

Vishal Suthar
Vishal Suthar

Reputation: 17183

No..It is not mandatory to check (dr.HasRows) if the DataReader contains any row or not.

Read() will return False if there are no more rows to fetch, but Reader.HasRows is much more telling as to what it does than Read() so it would be a good practice to use Reader.HasRows because you may accidentally do something other than Read() which may fall into exception.

Upvotes: 19

Abbas
Abbas

Reputation: 14432

It's not mandatory to check if the DataReader has rows (dr.HasRows). The Read() method will return true if there is more data to read and false if there's no more data, thus breaking the while-loop.

Upvotes: 2

TomTom
TomTom

Reputation: 62093

I think this is mostly for stored procedures which may or may not have data (one or more result sets) and it is "easier" to check first in case you also do other stuff than the while loop (i.e. initialize header/footer etc. when there is data).

Upvotes: 1

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