Question

尝试使用自定义比较器Distinct()，它会给我错误：

无法从使用中推断出来。尝试明确指定类型参数

Default比较器工作正常，但没有给出我期望的结果。我该如何解决这个问题？

public class TimeEntryValidation
{
    public string EmployeeID { get; set; }
    public string EmployeeLocation { get; set; }
    public string EmployeeDepartment { get; set; }
    public int RowIndex { get; set; }
}

public class MyRowComparer : IEqualityComparer<TimeEntryValidation>
{
    public bool Equals(TimeEntryValidation x, TimeEntryValidation y)
    {
        return (x.EmployeeDepartment == y.EmployeeDepartment && x.EmployeeLocation == y.EmployeeLocation);
    }

    public int GetHashCode(TimeEntryValidation obj)
    {
        return obj.EmployeeID.GetHashCode(); 
    }
}

void Query(List<TimeEntryValidation> listToQuery)
{
    var groupedData =
        from oneValid in listToQuery
        group oneValid by oneValid.EmployeeID
            into g
        where g.Count() > 1
        select new {DoubleItems = g};
    var listItems = groupedData.Distinct(new MyRowComparer());
}

Answer 1

groupedData的类型为IEnumerable<{an anonymous type}>，而MyRowComparer为IEqualityComparer<TimeEntryValidation>

目前还不清楚您是否打算将listItems作为一个群组列表，或者您是否想要实际的项目。

如果是后者，你可能想要这样的东西：

void Query(List<TimeEntryValidation> listToQuery)
{
    var groupedData = from oneValid in listToQuery
                        group oneValid by oneValid.EmployeeID
                            into g
                            where g.Count() > 1
                            select  g ;
    var listItems = groupedData.SelectMany(group => group).Distinct(new MyRowComparer());
    //listItems is now an IEnumerable<TimeEntryValidation>
}

与自定义比较器不同

1 个答案: