與LINQ聲明

Question

處理空值我有一個LINQ聲明，看起來像這樣：

List<Product> products = Product.GetAll(); 
List<Department> departments = Deparment.GetAll(); 

var productList = (from product in products 
       select new 
       { 
       ProductId= product.ID, 
       ProductName = product.Name, 
       Departments = departments.Where(d => product.DepartmentIDs.Contains(d.Id)).ToList() 
       }); 

我的問題是，在product.DepartmentIDs字段可能爲空。這是由於最近的數據庫更改。此更改導致我的代碼中斷。如果product.DepartmentIDs不爲空，我如何更新檢索部門的Where子句以僅獲取部門？ product.DepartmentIDs將是null或List<int>。

Answer 1

departments.Where(d => 
     product.DepartmentIDs != null && product.DepartmentIDs.Contains(d.Id)).ToList()