从C＃列表中选择不同的值 [英] Select Distinct Values from C# List

问题描述

我在Linq语句下面有以下内容，我用它来选择列表中有多少值myList

I have the following below Linq Statement which I use to select how many Value I have in a list myList

        class MyClassDetails
        {
            public string ID;
            public int Value;
        }

        class MyClass
        {
            public MyClass()
            {
                moreDetails = new ObservableCollection<MyClassDetails>();
            }
            public string Name;
            public ObservableCollection<MyClassDetails> moreDetails;
        }

        static void Main(string[] args)
        {
            var myList = new List<MyClass>();

            var myClass1 = new MyClass();
            myClass1.Name = "Class1";
            myClass1.moreDetails.Add(new MyClassDetails() { Value = 1, ID="ONE" });
            myClass1.moreDetails.Add(new MyClassDetails() { Value = 2, ID = "TWO" });
            myClass1.moreDetails.Add(new MyClassDetails() { Value = 4, ID = "ONE" });
            myClass1.moreDetails.Add(new MyClassDetails() { Value = 8, ID = "TWO" });
            myClass1.moreDetails.Add(new MyClassDetails() { Value = 16, ID = "ONE" });

            var myClass2 = new MyClass();
            myClass2.Name = "Class2";
            myClass2.moreDetails.Add(new MyClassDetails() { Value = 1, ID = "TWO" });
            myClass2.moreDetails.Add(new MyClassDetails() { Value = 2, ID = "ONE" });
            myClass2.moreDetails.Add(new MyClassDetails() { Value = 4, ID = "ONE" });
            myClass2.moreDetails.Add(new MyClassDetails() { Value = 8, ID = "TWO" });
            myClass2.moreDetails.Add(new MyClassDetails() { Value = 54, ID = "ONE" });

            myList.Add(myClass1);
            myList.Add(myClass2);

            var groups2 = myList.SelectMany(myClass => myClass.moreDetails, (myClass, details) => new { details.Value, myClass.moreDetails })
                                .GroupBy(myClass => myClass.Value)
                                .Select(g => new { Value = g.Key, Count = g.ToList().Distinct().Count() });


            foreach (var group in groups2)
            {
                var value = group.Value;

var count = group.Count;
}

var count = group.Count; }

所以上面会输出以下内容：

So the above will output the following:

group1：Value 1 Count 2

group1: Value 1 Count 2

group2：值2计数2

group2: Value 2 Count 2

group3：值4计数2

group3: Value 4 Count 2

group4：值8计数2

group4: Value 8 Count 2

group5：Value 54 Count 1

group5: Value 54 Count 1

我只想按ID计算不同的值

I want to only count the Distinct Values by ID

因此，对于上述情况，第3组和第4组只有count = 1，因为它们具有相同的ID值

So for the above the groups 3 and 4 would only have count=1 as they have the same ID values

group3：Value 4 Count 1

group3: Value 4 Count 1

group4：值8计数1

group4: Value 8 Count 1

如何修改查询以执行此操作？

How do I modify my query to do this?

推荐答案

试试这个：

var groups3 = myList
                 .SelectMany( c => c.moreDetails )
                 .GroupBy( d => d.Value )
                 .Select( g => new { Value = g.Key, Count = g.GroupBy( d => d.ID ).Count() } );

这个：

var groups4 = myList
                 .SelectMany( c => c.moreDetails )
                 .GroupBy( d => d.Value, ( k, e ) => new { Value = k, Count = e.GroupBy( d => d.ID ).Count() } );

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