c#

我有三个字段，我想根据它们过滤我的结果。我用了一个 if-else 语句，但它很尴尬，根据我的领域，我不得不写一些 if blocks 语句。有没有更简单的方法来做到这一点？

public ActionResult Search(String title, int? category_id, string productCode)
{
    IEnumerable<products> result;
    using (DBModels db = new DBModels())
    {
        if (title != null && category_id == null && productCode == null)
        {
            result = db.products.Where(c => c.title.Contains(title))
                                .Include(x => x.media)
                                .Include(p => p.categories)
                                .ToList();

            return View(result);
        }
        else if (category_id != null && title == null && productCode == null)
        {
            result = db.products.Where(c => c.category_id == category_id)
                                .Include(x => x.media)
                                .Include(p => p.categories)
                                .ToList();

            return View(result);
        }
        else if (productCode != null && title == null && category_id == null)
        {
            result = db.products.Where(c => c.id.ToString().Contains(productCode))
                                .Include(x => x.media)
                                .Include(p => p.categories)
                                .ToList();

            return View(result);
        }
        else if (productCode != null && title != null && category_id != null)
        {
            result = db.products.Where(c => c.title.Contains(title) 
                                         && c.category_id == category_id 
                                         && c.id.ToString().Contains(productCode))
                                .Include(x => x.media)
                                .Include(p => p.categories)
                                .ToList();
        }
    }

    result = db.products.Where(c => c.title.Contains(title) 
                                 || c.category_id == category_id 
                                 || c.id.ToString().Contains(productCode))
                        .Include(x => x.media)
                        .Include(p => p.categories)
                        .ToList();

    return View(result);
}

回答

public ActionResult Search(string title, int? category_id, string productCode)
{
    IEnumerable<products> result;
    using (DBModels db = new DBModels())
    {
        var query = db.products
                      .Include(x => x.media)
                      .Include(p => p.categories)
                      .AsQueryable();

        if (!string.IsNullOrWhiteSpace(title))
        {
            query = query.Where(c => c.title.Contains(title));
        }

        if ( category_id != null)
        {
            query = query.Where(c => c.category_id == category_id);
        }

        if (!string.IsNullOrWhiteSpace(productCode))
        {
            query = query.Where(c => c.id.ToString().Contains(productCode));
        }

        result = query.ToList();
        return View(result);
    }
}