/// <summary>
    /// Loads control.
    /// </summary>
    private void LoadControl()
    {
        // Get all product categories with options which are already in variants
        if (VariantCategoriesOptions.Count == 0)
        {
            DataSet variantCategoriesDS = VariantHelper.GetProductVariantsCategories(ProductID);
            FillCategoriesOptionsDictionary(VariantCategoriesOptions, variantCategoriesDS);
        }

        // Get all product attribute categories with options
        if (AllCategoriesOptions.Count == 0)
        {
            DataSet allCategoriesDS = OptionCategoryInfoProvider.GetProductOptionCategories(ProductID, true, OptionCategoryTypeEnum.Attribute);
            FillCategoriesOptionsDictionary(AllCategoriesOptions, allCategoriesDS);
        }

        foreach (KeyValuePair <OptionCategoryInfo, List <SKUInfo> > keyValuePair in AllCategoriesOptions)
        {
            if (keyValuePair.Value.Count > 0)
            {
                OptionCategoryInfo optionCategory = keyValuePair.Key;

                // Create new instance of CheckBoxWithDropDown control and prefill all necessary values
                CheckBoxWithDropDown checkBoxWithDropDown = new CheckBoxWithDropDown();
                checkBoxWithDropDown.ID    = ValidationHelper.GetString(optionCategory.CategoryID, string.Empty);
                checkBoxWithDropDown.Value = optionCategory.CategoryID;
                // Use live site display name instead of category display name in case it is available
                checkBoxWithDropDown.CheckboxText = HTMLHelper.HTMLEncode(ResHelper.LocalizeString(optionCategory.CategoryTitle));

                // Attach listeners
                checkBoxWithDropDown.OnCheckBoxSelectionChanged += checkBoxWithDropDown_OnCheckBoxSelectionChanged;
                checkBoxWithDropDown.OnDropDownSelectionChanged += checkBoxWithDropDown_OnDropDownSelectionChanged;

                // Option category is in variants too
                if (VariantCategoriesOptions.Keys.Any(c => ValidationHelper.GetInteger(c["categoryId"], 0) == optionCategory.CategoryID))
                {
                    // Check and disable checkbox
                    checkBoxWithDropDown.CheckboxChecked = true;
                    checkBoxWithDropDown.Enabled         = false;

                    // Already existing variants add to selected categories too
                    if (!SelectedCategories.ContainsKey(optionCategory.CategoryID))
                    {
                        SelectedCategories.Add(optionCategory.CategoryID, VariantOptionInfo.ExistingSelectedOption);
                    }
                }
                // Option category is not in variant, but some categories in variants already exists
                else if (VariantCategoriesOptions.Count > 0)
                {
                    // Set prompt message and visibility
                    checkBoxWithDropDown.DropDownPrompt  = GetString("general.pleaseselect");
                    checkBoxWithDropDown.DropDownLabel   = GetString("com.variants.dropdownlabel");
                    checkBoxWithDropDown.DropDownVisible = true;

                    // Get all product options and bind them to dropdownlist
                    var options       = SKUInfoProvider.GetSKUOptionsForProduct(ProductID, optionCategory.CategoryID, true).OrderBy("SKUOrder");
                    var dropDownItems = new ListItemCollection();

                    foreach (var option in options)
                    {
                        dropDownItems.Add(new ListItem(option.SKUName, option.SKUID.ToString()));
                    }

                    checkBoxWithDropDown.DropDownItems = dropDownItems;
                }

                // Finally bind this control to parent
                chboxPanel.Controls.Add(checkBoxWithDropDown);
            }
        }
    }