加载集合除了使用linq的另一个集合 [英] Load collection except another collection using linq

问题描述

我有这个搜索方法：

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Employee类的集合，说BadEmployeees，我想要的是使用相同的以前的方法返回除BadEmployeees之外的所有Employee。

I have another collection of Employeees, say "BadEmployeees", what I want is using the same previous method to return all Employeees except "BadEmployeees".

我尝试这样写：

return context.Employeees.Where(
        x => x.EmployeeeName.Contains(keyword)
        && x.EmployeeeTypeId == employeeeTypeId)
    .Except(BadEmployeees).Take(count).ToList();

但它是一个例外，除可以使用Int，Guid等数据类型。

But it is giving an exception that Except can just work with data types such as Int, Guid,...

推荐答案

如果您很乐意检索所有数据然后执行except，这是比较容易的：

If you're happy to retrieve all the data and then perform the "except", that's relatively easy:

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();

或者：

// 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();

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