DISTINCT與自定義比較

Question

嘗試使用自定義比較使用Distinct()，它給我的錯誤：

cannot be inferred from the usage. Try specifying the type arguments explicitly

的Default比較器工作正常，但不能給予我期待當然的結果。我怎樣才能解決這個問題？

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

類型的groupedData一些IEnumerable<{an anonymous type}>而MyRowComparer是IEqualityComparer<TimeEntryValidation>

目前還不清楚你是否打算listItems是組列表，或者您是否要實際的項目本身。

如果是後者，你可能想是這樣的：

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> 
}