I am trying to create a select statement in C# to check if the value inserted into a textbox (userName) is in an existing SQL database. I have a database called Employee containing a table called EVUSERS and it has a column called UName.

In my code I have a method which takes the value from a textbox called UserBox. I would like to know if there is a temporary table where the select is stored which I can compare the textbox value to.

Here is the code:

private void CheckLoginExist()
{
            String userName = UserBox.Text;
            string connectionString = @"Data Source=.\SQLEXPRESS;Database=Employee;Integrated Security=true";
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand command = connection.CreateCommand())
                {
                    command.CommandText = "SELECT UName FROM EVUSERS WHERE UName = @UName";
                    command.Parameters.AddWithValue("@UName", userName);
                    connection.Open();
                    command.ExecuteNonQuery();
                    connection.Close();
                }
            }
}