wpf 按多列对 C# 列表进行排序
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Sorting a C# List by multiple columns
提问by isakavis
I have a question on sorting a list by multiple columns. In the following sample, even though I sorted to show None, A First Description, B Second..., the list still prints in the order it was inserted.
我有一个关于按多列对列表进行排序的问题。在下面的示例中，即使我排序为 show None, A First Description, B Second...，列表仍按插入顺序打印。
List<MySample> samples = new List<MySample>();
samples.Add(new MySample { SortOrder = 1, Data = "A First Description", Description = "A First Description" });
samples.Add(new MySample { SortOrder = 1, Data = "C Third Description", Description = "C Third Description" });
samples.Add(new MySample { SortOrder = 1, Data = "B Second Description", Description = "B Second Description" });
samples.Add(new MySample { SortOrder = 0, Data = "None", Description = "None" });
samples.OrderBy(a => a.SortOrder).ThenBy(a => a.Description).ToList();
foreach (var item in samples)
{
Console.WriteLine(item);
}
public class MySample
{
public int SortOrder { get; set; }
public string Description { get; set; }
public object Data { get; set; }
}
If I change my code to do the following, then it prints in the desired order.
如果我更改代码以执行以下操作，则它会按所需顺序打印。
samples = samples.OrderBy(a => a.SortOrder).ThenBy(a => a.Description).ToList();
Can the ordering be done without assigning(like above)?
可以在不分配的情况下完成订购吗（如上）？
FYI, this example is not actual code. I need to databind this list to a ComboBoxin WPFthrough code behind using FrameworkElementFactory.
仅供参考，此示例不是实际代码。我需要数据绑定该列表到ComboBox在WPF通过后面的代码使用FrameworkElementFactory。
Thanks for your help!
谢谢你的帮助！
Update with my approach:
用我的方法更新：
var collectionView = CollectionViewSource.GetDefaultView(<My list to be sorted>);
collectionView.SortDescriptions.Add(new SortDescription("SortOrder", ListSortDirection.Ascending));
collectionView.SortDescriptions.Add(new SortDescription("Description", ListSortDirection.Ascending));
The above did the trick in the UI. I thank all for the fast answers.
以上在 UI 中起到了作用。我感谢所有人的快速答复。
回答by musefan
The reason is because OrderBydoes not transform the object it is called on, instead it returns a new result. You should use it like this:
原因是因为OrderBy它不会转换它被调用的对象，而是返回一个新的结果。你应该像这样使用它：
samples = samples.OrderBy(a => a.SortOrder).ThenBy(a => a.Description).ToList();
This is the way the OrderByfunction works. Why would you need it to work the other way, especially for just a few extra characters.
这就是OrderBy函数的工作方式。为什么你需要它以另一种方式工作，尤其是对于几个额外的字符。
You couldmake it work, by creating your own extension methods that do the same thing except work on the reference to the object rather than creating a new result, but this is not worth the trouble at all.
您可以通过创建自己的扩展方法来使其工作，除了处理对对象的引用而不是创建新结果之外，这些方法可以做同样的事情，但这根本不值得麻烦。
If you need something though, you could just wrap the LINQ in an extension method like so:
如果你需要一些东西，你可以将 LINQ 包装在一个扩展方法中，如下所示：
public static void MyOrderBy(this List<MySample> list)
{
list = list.OrderBy(a => a.SortOrder).ThenBy(a => a.Description).ToList();
}
and the use it like so:
并像这样使用它：
samples.MyOrderBy();
It's just an idea though, I don't know if it will work, or if it's a good idea or not.
这只是一个想法，我不知道它是否会奏效，或者它是否是一个好主意。
回答by Joe Enos
Since you have a List, you can do it the old school way:
既然你有一个List，你可以用老派的方式来做：
samples.Sort((s1, s2) => {
int compare = s1.SortOrder.CompareTo(s2.SortOrder);
if (compare != 0) return compare;
compare = s1.Description.CompareTo(s2.Description);
return compare;
});
But I'd probably stick with LINQ. Much easier to read.
但我可能会坚持使用 LINQ。更容易阅读。
回答by Tim S.
You could change your example to:
您可以将示例更改为：
//other code above...
samples.Add(new MySample { SortOrder = 0, Data = "None", Description = "None" });
foreach (var item in samples.OrderBy(a => a.SortOrder).ThenBy(a => a.Description))
//other code below...
Note that samplesis unchanged by the ordering - only the order for that particular loop-through is set.
请注意，samples排序不会改变 - 仅设置了该特定循环的顺序。
If neither of these are acceptable, please explain your need in more detail.
如果这些都不可接受，请更详细地说明您的需求。
回答by JerKimball
Just for an alternative, "please don't do this unless nothing else fits" route, you couldadd a new property to sort on an amalgamation:
只是为了替代，“除非没有其他合适的东西，否则请不要这样做”路线，您可以添加一个新属性来对合并进行排序：
class NoReallyThisIsACodeSmell
{
public string SortPlusDescription
{
return string.Concat(SortOrder, Description);
}
}
