動態LINQ2Entities查詢無法將IEnumerable轉換爲bool

Question

這裏的建立和組織行給出了它們不能將IEnumerable隱式轉換爲bool的錯誤。我錯過了什麼？在方法結束之前，我不能使用貪婪的操作符。我相信這很簡單，但我看不到它。

IQueryable<User> query = context.Users; 

if (usvm.EstablishmentId > 0) 
    query = query.Where(x => x.UserEstablishments 
     .Where(y => y.UserEstablishmentId == usvm.EstablishmentId)); 

if (usvm.OrganisationId > 0) 
    query = query.Where(x => x.UserEstablishments 
     .Where(y => y.Establishment.OrganisationId == usvm.OrganisationId)); 

if (!String.IsNullOrEmpty(usvm.Forename)) 
    query = query.Where(x => x.Forename == usvm.Forename); 

if (!String.IsNullOrEmpty(usvm.Surname)) 
    query = query.Where(x => x.Surname == usvm.Surname); 

if (usvm.DOB != null) 
    query = query.Where(x => x.DOB == usvm.DOB); 

List<User> m = query.ToList(); 
return ToViewModel(m); 

Answer 1

你可以使用Any方法：

if (usvm.EstablishmentId > 0) 
    query = query.Where(x => x.UserEstablishments 
     .Any(y => y.UserEstablishmentId == usvm.EstablishmentId)); 

if (usvm.OrganisationId > 0) 
    query = query.Where(x => x.UserEstablishments 
     .Any(y => y.Establishment.OrganisationId == usvm.OrganisationId));