C＃访问数据库查询

Question

I created database in ms access and it has GPA column. In listbox2 i need to list students which GPA is bigger than 2. how caN I do that?

command.CommandText = "SELECT * FROM Student WHERE GPA > 2";
while (reader.Read())
{
  listBox2.Items.Add............?
}

Help if you can.

Answer 1

I don't know if that's just pseudo code you've posted. But if not, you are reading a DataReader which is either not initialized or is not using the correct Command -sql since you are setting the CommandText one line before.

command.CommandText = "SELECT * FROM Student WHERE GPA > 2";
using(var reader = command.ExecuteReader())
{
    while (reader.Read())
    {
        // assuming that there's a column with name: StudentName
        listBox2.Items.Add(reader.GetString(reader.GetOrdinal("StudentName")));
    }
}

Answer 2

string ConnectionString = "PUT YOU CONNECTION STRING HERE";

con = new SqlConnection(ConnectionString);
con.Open();
string CommandText = "SELECT * FROM Student WHERE GPA > 2";
cmd = new SqlCommand(CommandText);
cmd.Connection = con;
rdr = cmd.ExecuteReader();
lbx.Items.Clear();
while (rdr.Read())
{    
     lbx.Items.Add......
}