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比较两个列表,使用lambda谓词确定两个列表是否包含相同的项

predicate lambda vb.net c#

Popo · 技术社区 · 7 年前

如果我的对象列表包含vb中类型列表中的所有类型,我试图返回一个布尔值。net或C#。我正在努力写一个lambda表达式来实现这一点。使用lambda谓词可以实现吗?我知道用for-each循环可以很容易地完成。

vb。网

Public Class Widget
    Public wobbly As String
    Public sprocket As String
    Public bearing As String
End Class

Public Sub test()
    Dim wList As New List(Of Widget)
    wList.Add(New Widget() With {.bearing = "xType", .sprocket = "spring", .wobbly = "99"})
    wList.Add(New Widget() With {.bearing = "yType", .sprocket = "sprung", .wobbly = "45"})
    wList.Add(New Widget() With {.bearing = "zType", .sprocket = "straight", .wobbly = "17"})

    Dim typeList As New List(Of String) From {"xType", "yType", "zType"}

    Dim containsAllTypes As Boolean = wList.TrueForAll(Function(a) a.bearing.Equals(typeList.Where(Function(b) b = a.bearing)))
    Debug.WriteLine(containsAllTypes.ToString)
End Sub

public class Widget
{
    public string wobbly;
    public string sprocket;
    public string bearing;
}

public void test()
{
    List<Widget> wList = new List<Widget>();
    wList.Add(new Widget {
        bearing = "xType",
        sprocket = "spring",
        wobbly = "99"
    });
    wList.Add(new Widget {
        bearing = "yType",
        sprocket = "sprung",
        wobbly = "45"
    });
    wList.Add(new Widget {
        bearing = "zType",
        sprocket = "straight",
        wobbly = "17"
    });

    List<string> typeList = new List<string> {
        "xType",
        "yType",
        "zType"
    };

    bool containsAllTypes = wList.TrueForAll(a => a.bearing.Equals(typeList.Where(b => b == a.bearing)));
    Debug.WriteLine(containsAllTypes.ToString());
}

编辑,感谢所有的快速回答,我知道有几种方法可以做到这一点,现在对表达式中发生的事情有了更好的理解。

7 回复 | 直到 7 年前

Matt.G 7 年前

尝试 var containsAllTypes = typeList.All(x => wList.Select(x => x.bearing).Contains(x))

Scott Hannen 7 年前

var containsAll = typeList.All(type => 
    wList.Any(widget => widget.bearing.Equals(type)));

翻译过来,它适用于所有类型的 typeList 列表中的任何(至少一个)小部件都具有该类型。

Michael Erickson 7 年前

我相信你想要的是:

bool containsAllTypes1 = wList.TrueForAll(a => null != typeList.Find(b => b == a.bearing));

你也可以使用这个系统。Linq如下:

bool containsAllTypes2 = wList.All(a => typeList.Any(b => b == a.bearing));

RogerMKE 7 年前

 Dim containsAllTypes As Boolean = wList.All(Function(a) typeList.Any(Function(b) b = a.bearing))

对于wList中的每个值,它会检查typeList中是否有任何值与wList轴承值匹配。

tschmit007 7 年前

越短越好

containsAllTypes = wList.Where(x => typeList.Contains(x.bearing)).Count() == typeList.Count;

或

containsAllTypes =  wList.Select(x => x.bearing).Except(typeList).Count() == 0;

或

containsAllTypes =  wList.Select(x => x.bearing).Intersect(typeList).Count() == typeList.Count;

Aleks Andreev Md. Suman Kabir 7 年前

你可以用 Intersect 检查两个列表是否具有相同的值。试试这个代码

var hasAll = wList
 .Select(w => w.bearing)
 .Distinct()
 .Intersect(typeList)
 .Count() == typeList.Count;

如果你需要 hasAll == true 只有当所有类型 wList 发生一次,删除对的调用 Distinct