实体框架对具有列表的实体应用过滤器

Question

I have this code using Entity Framework

 var test = _dbContext.Category
                      .Include(t => t.Items)
                      .Where(t => t.items.show == true)
                      .ToList();

A category has a list of items. However, I can not apply the filter show == true .

Why is it happening? How do I fix it?

Thanks

Answer 1

The items in t=>t.items.show==true is a collection not the individual item, so there is no show property.

If you need to load only the items with show==true you can load them separately:

var categories = _dbContext.Category.ToList();
var items = _dbContext.Category.SelectMany(x => x.Items).Where(x => x.show == true).ToList();

EF will attach the items to appropriate categories automatically.

Answer 2

You can use Any for this kind of request and you may avoid Include if you won't use items apart from filtering.

var test = _dbContext.Category
                      .Where(t => t.items.Any(item=> item.show == true))
                      .ToList();

PS: I strongly recommend to use C# naming convention. Items and Show are more accurate if they are properties.