The following code contains a few nested async calls within some foreach loops. I know the silverlight/wcf calls are called asyncrously -but how can I ensure that my wcfPhotographers, wcfCategories and wcfCategories objects are ready before the foreach loop start? I'm sure I am going about this all the wrong way -and would appreciate an help you could give.

    private void PopulateControl()
    {

        List<CustomPhotographer> PhotographerList = new List<CustomPhotographer>();

        proxy.GetPhotographerNamesCompleted += proxy_GetPhotographerNamesCompleted;
        proxy.GetPhotographerNamesAsync();


        //for each photographer
        foreach (var eachPhotographer in wcfPhotographers)
        {

            CustomPhotographer thisPhotographer = new CustomPhotographer();

            thisPhotographer.PhotographerName = eachPhotographer.ContactName;
            thisPhotographer.PhotographerId = eachPhotographer.PhotographerID;

            thisPhotographer.Categories = new List<CustomCategory>();

            proxy.GetCategoryNamesFilteredByPhotographerCompleted += proxy_GetCategoryNamesFilteredByPhotographerCompleted;
            proxy.GetCategoryNamesFilteredByPhotographerAsync(thisPhotographer.PhotographerId);


            // for each category
            foreach (var eachCatergory in wcfCategories)
            {

                CustomCategory thisCategory = new CustomCategory();

                thisCategory.CategoryName = eachCatergory.CategoryName;
                thisCategory.CategoryId = eachCatergory.CategoryID;

                thisCategory.SubCategories = new List<CustomSubCategory>();

                proxy.GetSubCategoryNamesFilteredByCategoryCompleted += proxy_GetSubCategoryNamesFilteredByCategoryCompleted;
                proxy.GetSubCategoryNamesFilteredByCategoryAsync(thisPhotographer.PhotographerId,thisCategory.CategoryId);

                // for each subcategory
                foreach(var eachSubCatergory in wcfSubCategories)
                {
                    CustomSubCategory thisSubCatergory = new CustomSubCategory();

                    thisSubCatergory.SubCategoryName = eachSubCatergory.SubCategoryName;
                    thisSubCatergory.SubCategoryId = eachSubCatergory.SubCategoryID;
                }


                thisPhotographer.Categories.Add(thisCategory);
            }

            PhotographerList.Add(thisPhotographer);
        }

        PhotographerNames.ItemsSource = PhotographerList;
    }




    void proxy_GetPhotographerNamesCompleted(object sender, GetPhotographerNamesCompletedEventArgs e)
    {
        wcfPhotographers = e.Result.ToList();
    }


    void proxy_GetCategoryNamesFilteredByPhotographerCompleted(object sender, GetCategoryNamesFilteredByPhotographerCompletedEventArgs e)
    {
        wcfCategories = e.Result.ToList();
    }

    void proxy_GetSubCategoryNamesFilteredByCategoryCompleted(object sender, GetSubCategoryNamesFilteredByCategoryCompletedEventArgs e)
    {
        wcfSubCategories = e.Result.ToList();
    }