Open DataReader associated with this Command which must be closed first problem

I got this error coming up.
I populate all ddl controls on the master page from the database. I include one of my methods for selecting data from the database. Am I doing everything how I suppose to do it?
The error is "There is already an open DataReader associated with this Command which must be closed first."
public static DataTable populateFavoriteRecipes(int userId) { string query = @"SELECT recipes.recipeid, recipes.category, Substring(recipes.title, 0, 120) AS title, CONVERT(VARCHAR(19), recipes.postedon) AS postedOn, Substring(recipes.directions, 0, 250) + '.....' AS directions, recipes.timetoprepare, recipes.calories, ...