仅当组中的所有项目均为“ true”时，才对linq进行计数

Question

Given the sample data below, I need a linq query that returns the number of items that are in stock at all 3 warehouses. In the example below, it should return 2 , because only skus ABC-123 and JKL-789 are ins stock at all 3 warehouses. But my query is returning 3?

WarehouseId     Sku         InStock
===================================
1               ABC-123     true
2               ABC-123     true
3               ABC-123     true

1               XYZ-789     true
2               XYZ-789     false
3               XYZ-789     true

1               JKL-456     true
2               JKL-456     true
3               JKL-456     true




int inStock = query.Where(x => x.InStock).GroupBy(x => x.Sku).Count();

Answer 1

Your query returns 3 because your Count() is unrestricted, meaning that it counts all groups, not only the ones with all items present in stock.

Add a condition with a call to All(item => item.InStock) to count only the items that you need:

var inStock = query
    .GroupBy(x => x.Sku)
    .Count(g => g.All(item => item.InStock));

Note that Where is now gone, so that all items are included in groups.

Answer 2

int inStock = query
                .Where(x => x.InStock)
                .GroupBy(x => x.Sku)
                .Where(g=>g.Count() == 3)
                .Count();

Althought dasblinkenlight solution is better, as it covers adding new warehouses.