I think the suggestions in previous comment are all correct.
I would just refactor the code a bit as following:
public class SomeDataAccessClass
public bool IsPhoneNumberPresent(string number)
bool returnVal = false;
using(MySqlConnection conn = new MySqlConnection(connection))
using (SqlCommand cmd = con.CreateCommand())
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select count(*)from table.alladmin where number = @number";
SqlParameter param = new SqlParameter("@number", number);
int result = (int)cmd.ExecuteScalar();
returnVal = result >= 1;
Still Not perfect but I could live with this code. I hope you will understand the code. If not, ask.