C# 将上下文中的多个结果追加到一个列表（结果）不起作用

我正在开发小型.net应用程序，我需要按其类型获取文章，可能有3种类型：

食物 喝 糖果 我想知道，如果我想在食物和饮料的相同列表文章中，如何将上下文的结果添加到另一个结果中，而不重置它

这是我目前的代码：

public async Task<IEnumerable<Article>> GetArticlesByType(ArticleObject request)
{
var result = new Article[] { }.AsQueryable();
IQueryable<ArticleDTO> query = null;

if (request.Food.HasValue && (bool)request.Food)
{
    // Return type of query is IQueryable<Article> 
    query = _context.Articles.Where(x => x.Active == true && x.ArticleType == ArticleType.Food).Select(x => new Article
    {
        Id = x.Id,
        ArticleName = x.ArticleName
    });
    // Here I just wanted if this condition is satisfied to add values to my result
    result.AsQueryable().Union(query);
}

if (request.Drink.HasValue && (bool)request.Drink)
{
    query = _context.Articles.Where(x => x.Active == true && x.ArticleType == ArticleType.Drink).Select(x => new Article
    {
        Id = x.Id,
        ArticleName = x.ArticleName
    });
    // Again if there are any values in query add them to existing result values
    result.AsQueryable().Union(query);
}

if (request.Candy.HasValue && (bool)request.Candy)
{
    // When its candy I want also articles from food category
    query = _context.Articles.Where(x => x.Active == true && x.ArticleType == ArticleType.Food || x.ArticleType==ArticleType.Candy).Select(x => new Article
    {
        Id = x.Id,
        ArticleName = x.ArticleName
    });
    // Again if there are values in query add them to existing result 
    result.AsQueryable().Union(query);
}
//At the end return result and all the values in case all conditions were satisfied
return await result.ToListAsync();

}

现在，我已经尝试向result变量添加值，但即使查询中有一些数据，结果始终是空的

查询正在返回IQueryable，因此我无法创建接口的任何内容的空列表，因为我无法对其进行初始化

谢谢各位 干杯

谢谢各位

---

干杯

谢谢您的帮助，请查看我的编辑。投票！

    public async Task<IEnumerable<Article>> GetArticlesByType(ArticleObject request)
{
    IQueryable<ArticleDTO> foodArticles= null;
    IQueryable<ArticleDTO> drinkArticles= null;
    IQueryable<ArticleDTO> candyArticles= null;

    if (request.Food.HasValue && (bool)request.Food)
    {
        foodArticles= _context.Articles.Where(x => x.Active == true && x.ArticleType == ArticleType.Food).Select(x => new Article
        {
            Id = x.Id,
            ArticleName = x.ArticleName
        });
    }

    if (request.Drink.HasValue && (bool)request.Drink)
    {
        drinkArticles= _context.Articles.Where(x => x.Active == true && x.ArticleType == ArticleType.Drink).Select(x => new Article
        {
            Id = x.Id,
            ArticleName = x.ArticleName
        });
    }

    if (request.Candy.HasValue && (bool)request.Candy)
    {
        // When its candy I want also articles from food category
        candyArticles= _context.Articles.Where(x => x.Active == true && x.ArticleType == ArticleType.Food || x.ArticleType==ArticleType.Candy).Select(x => new Article
        {
            Id = x.Id,
            ArticleName = x.ArticleName
        });
    }
    return await foodArticles.AsQueryable().Union(drinkArticles).AsQueryAble().Union(candyArticles);
}