我有这种搜索方法:
public List<Employeees> AutoSuggestEmployeee(string keyword,
long employeeeTypeId, int count)
{
return context.Employeees.Where(
x => x.EmployeeeName.Contains(keyword)
&& x.EmployeeeTypeId == employeeeTypeId)
.Take(count).ToList();
}
我有另一个员工集合,说“BadEmployeees”,我想要的是使用相同的先前方法返回除“BadEmployeees”之外的所有员工。
我试着这样写:
return context.Employeees.Where(
x => x.EmployeeeName.Contains(keyword)
&& x.EmployeeeTypeId == employeeeTypeId)
.Except(BadEmployeees).Take(count).ToList();
但它提供了一个例外,即Except
可以使用Int,Guid等数据类型......
答案 0 :(得分:7)
Except
方法进行比较,因此必须知道如何比较对象。对于简单类型,有标准比较,但对于复杂类型,您需要提供一个比较对象中相关数据的相等比较器。
示例:
class EmployeeComparer : IEqualityComparer<Employeees> {
public bool Equals(Employeees x, Employeees y) {
return x.Id == y.Id;
}
public int GetHashCode(Employeees employee) {
return employee.Id.GetHashCode();
}
}
用法:
return
context.Employeees
.Where(x => x.EmployeeeName.Contains(keyword) && x.EmployeeeTypeId == employeeeTypeId)
.Except(BadEmployeees, new EmployeeComparer())
.Take(count)
.ToList();
答案 1 :(得分:6)
如果您很乐意检索所有数据并然后执行“除外”,那就相对容易了:
return context.Employees
.Where(x => x.EmployeeName.Contains(keyword)
&& x.EmployeeTypeId == employeeeTypeId)
// Limit the data *somewhat*
.Take(count + BadEmployees.Count)
// Do the rest of the query in-process
.AsEnumerable()
.Except(BadEmployees)
.Take(count)
.ToList();
可替换地:
// I'm making some assumptions about property names here...
var badEmployeeIds = badEmployees.Select(x => x.EmployeeId)
.ToList();
return context.Employees
.Where(x => x.EmployeeName.Contains(keyword)
&& x.EmployeeTypeId == employeeeTypeId)
&& !badEmployeeIds.Contains(x.EmployeeId))
.Take(count)
.ToList();