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问题:
I'm developing an ASP.NET MVC 4 Application and I'm trying to run this Lambda expression in Entity Framework 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));
I get this error :
Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<ITKaranDomain.GNL_CustomerLaptopProduct>' to 'bool'
I know that the last where clause is wrong but I don't know how to correct it.
回答1:
You might want another .Any instead of a .Where in your .Any clause at the end:
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));
回答2:
Use Where ( Any ) in last statement to select customers which have at least one product satisfying your conditions:
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));
