Question

我已经通过基于此nested group example的查询得到了一个嵌套的LINQ组，它为同一个DateTime创建了多个键。

var queryNestedGroups =
    from lockAssignment in db.LockAssignment
    where lockAssignment.UserId == userIdForUsername
    group lockAssignment by lockAssignment.DateStart into lockAssignmentsByDateGroup
    from lockAssignmentsByZoneGroup in
        (from lockAssignment in lockAssignmentsByDateGroup
         group lockAssignment by lockAssignment.Lock.Zone.ZoneName)
    group lockAssignmentsByZoneGroup by lockAssignmentsByDateGroup.Key;

// Three nested foreach loops are required to iterate  
// over all elements of a grouped group. Hover the mouse  
// cursor over the iteration variables to see their actual type. 
foreach (var outerGroup in queryNestedGroups)
{
    Debug.WriteLine("outerGroup.Key = {0}", outerGroup.Key);
    foreach (var innerGroup in outerGroup)
    {
        Debug.WriteLine("\tinnerGroup.Key: {0}", innerGroup.Key);
        foreach (var innerGroupElement in innerGroup)
        {
            Debug.WriteLine("\t\tinnerGroupElement: {0}, innerGroupElement.DateStart: {1}", innerGroupElement, innerGroupElement.DateStart);
        }
    }
}

这是控制台输出：

outerGroup.Key = 03/11/2015 10:45:55
Jewelry:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
Watches:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
outerGroup.Key = 03/11/2015 10:45:55
Watches:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55

我希望03/11/2015只能看到一个outerGroup.Key，如下所示：

outerGroup.Key = 03/11/2015 10:45:55
Jewelry:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
Watches:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55

我有没有办法让outerGroup.Key更多，包括类似的日期？

提前致谢！

Answer 1

你的代码似乎工作正常。我的猜测是日期不是很明显。

将顶级调试行更改为以下内容以打印毫秒（这是一个开始）。否则可能会有一些不同的东西让.NET相信日期不一样。

Console.WriteLine("outerGroup.Key = {0} {0:fff}", outerGroup.Key);

您可以使用以下代码

将代码更改为使用DateTime对象的更多特定属性进行分组

group lockAssignment by new {
        lockAssignment.Group.Year,
        lockAssignment.Group.Month
    } into lockAssignmentsByDateGroup

Answer 2

通过使用Kati的建议here，我能够得到我想要的分组，如下所示：

outerGroup.Key = { year = 2015, month = 3, day = 11 }
Jewelry:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
Watches:    innerGroup.Key: {0}
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55
        innerGroupElement: System.Data.Entity.DynamicProxies.LockAssignment_F0A35C00917489FA2C4D63DCAECAAD7A1EC03543B62C35206BF0542C5EAF1D8A, innerGroupElement.DateStart: 03/11/2015 10:45:55

这是更新的查询：

var queryNestedGroups =
    from lockAssignment in db.LockAssignment
    where lockAssignment.UserId == userIdForUsername
    let lockAssignmentStartDate = lockAssignment.DateStart
    group lockAssignment by new
    {
        year = lockAssignmentStartDate.Year,
        month = lockAssignmentStartDate.Month,
        day = lockAssignmentStartDate.Day
    } into lockAssignmentsByDateGroup
    from lockAssignmentsByZoneGroup in
        (from lockAssignment in lockAssignmentsByDateGroup
         group lockAssignment by lockAssignment.Lock.Zone.ZoneName)
    group lockAssignmentsByZoneGroup by lockAssignmentsByDateGroup.Key;

LINQ组通过为同一DateTime创建多个键

2 个答案: