Invalid operation exception

.NET
1

i have a question in invalid operation exception. it says that " ExecuteReader Connection is closed and must be open

SqlConnection conn = new SqlConnection("Server=localhost\\\\SqlExpress;" +
"Database=db;Integrated Security=True");
            SqlCommand comm = new SqlCommand("SELECT EmpID, Name FROM Employee", conn);
           
            SqlDataReader reader = comm.ExecuteReader();
2

ok,the problem solved

add this line before reader

comm.Connection.Open();

SqlConnection conn = new SqlConnection("Server=localhost\\\\SqlExpress;" +
"Database=db;Integrated Security=True");
            SqlCommand comm = new SqlCommand("SELECT EmpID, Name FROM Employee", conn);
            comm.Connection.Open();
            SqlDataReader reader = comm.ExecuteReader();
3

Make sure you close that connection and that reader. Best bet would be to wrap both in a using block:


using (var conn = new SqlConnection(cstring))
using (var cmd = conn.CreateCommand())
{
    cmd.CommandText="SELECT foo FROM bar";
    conn.Open();
    using (var r = cmd.ExecuteReader()){
        // do stuff
        r.Close();
    }
    conn.Close();
}
4

i like to add, if you would use the using you wont need to explicitly close the connection, .net would do that for you.

5

True, but I’d generally contend that it is better to have explicit intent rather than rely upon implicit behavior.