無法隱式轉換類型System.Collections.Generic.IEnumerable <>爲bool

Question

我開發一個ASP.NET MVC 4應用程序，我想在實體框架5

var customer = db.GNL_Customer.Where(d => d.GNL_City.FKProvinceID == advancedProvinceID || advancedProvinceID == null) 
      .Where(d => d.FKCityID == advancedCityID || advancedCityID == null) 
      .Where(d => d.FKDepartmentStoreID == advancedDepartmentStoreID || advancedDepartmentStoreID == null) 
      .Where(d => d.GNL_CustomerLaptopProduct.Where(r => String.Compare(r.BrandName, brandID) == 0 || brandID == null)); 

運行這個Lambda表達式

我得到這個錯誤：

Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<ITKaranDomain.GNL_CustomerLaptopProduct>' to 'bool'

我知道，最後的where子句是錯誤的，但我不知道如何糾正它。

Answer 1

您可能希望另一.Any代替.Where在年底你.Any條款：

var customer = db.GNL_Customer.Where(d => d.GNL_City.FKProvinceID == advancedProvinceID || advancedProvinceID == null) 
      .Where(d => d.FKCityID == advancedCityID || advancedCityID == null) 
      .Where(d => d.FKDepartmentStoreID == advancedDepartmentStoreID || advancedDepartmentStoreID == null) 
      .Any(d => d.GNL_CustomerLaptopProduct.Any(r => String.Compare(r.BrandName, brandID) == 0 || brandID == null)); 

Answer 2

使用Where (Any)在最後的陳述，選擇具有至少一個產品滿足您的條件的客戶：

var customer = db.GNL_Customer 
    .Where(d => d.GNL_City.FKProvinceID == advancedProvinceID || advancedProvinceID == null) 
    .Where(d => d.FKCityID == advancedCityID || advancedCityID == null) 
    .Where(d => d.FKDepartmentStoreID == advancedDepartmentStoreID || advancedDepartmentStoreID == null) 
    .Where(d => brandID == null || d.GNL_CustomerLaptopProduct.Any(r => r.BrandName == brandID));