Question

I have a WPF application which shows items in a DataGrid (XCeed DataGrid). The app takes a while to load when the database (SQLite) contains lots of items, so I’d like to use yield return if possible to load these on demand. I know the XCeed DataGrid supports UI virtualization, but I’m not entirely sure how to convert the following block of synchronous code.

Currently, the list of loaded in a BackgroundWorker to prevent UI slowdown, the populated as the grid’s DataSource.

   public override IList<IRecipe> GetRecipes()
    {
        List<IRecipe> recipes = new List<IRecipe>();
        Execute(conn =>
        {
            using (var cmd = conn.CreateCommand()) {
                cmd.CommandText = "SELECT * FROM recipes  ORDER BY Name";
                var reader = cmd.ExecuteReader();
                while (reader.Read()) {
                    try {
                        var recipe = GetRecipe(reader);
                        recipes.Add(recipe);
                    } catch (Exception ex) {
                        Console.WriteLine(string.Format("Error loading recipe: {0}", ex.Message));
                    }
                }
                reader.Close();

                cmd.CommandText = "SELECT * FROM Ingredients WHERE Recipe = @Recipe";
                cmd.Parameters.AddWithValue("@Recipe", string.Empty);
                foreach (IRecipe recipe in recipes) {
                    cmd.Parameters["@Recipe"].Value = recipe.ID;
                    reader = cmd.ExecuteReader();
                    while (reader.Read()) {
                        try {
                            IIngredient Ingredient = GetIngredient(reader);
                            recipe.Ingredients.Add(Ingredient);
                        } catch (Exception ex) {
                            Console.WriteLine(string.Format("Error adding Ingredient to recipe '{0}': {1}", recipe.Name, ex.Message));
                        }
                    }
                    reader.Close();
                }
            }

Alternatively is there any other way I could improve the speed and use lazy loading?

Answer 1

I’m not familiar exactly with how xceed fetches the virtualized items.
I assume it is by some kind of event that specifies what range of rows that are requested.

In the event (or whatever method that is used) you fetch a range of your query. Use LIMIT and OFFSET as noted at the bottom of the SELECT documentation.