比较两个列表以确定两个列表是否使用lambda谓词包含相同的项目

Question

I am trying to return a boolean value if my object list contains all the types in a list of types in either vb.net or C#. I am struggling in writing a lambda expression to accomplish this. Can this be done using lambda predicates? I know it can be done easily with a for each loop.

vb.net

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

C#

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());
}

EDIT, thanks for all the quick answers, I see there are a few ways to do this, and now have a better understanding of what is happening in the expression.

Answer 1

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

Answer 2

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

Translated, it is true for all types in typeList that any (at least one) widget in the list has that type.

Answer 3

I believe what you want is the following:

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

You can also use System.Linq as follows:

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

Answer 4

The shorter is

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

or

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

or

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

Answer 5

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

对于wList中的每个值，它将检查typeList中的任何值是否与wList方位值匹配。

Answer 6

You can use Intersect to check if both list has same values. Try this code

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

If you need to have hasAll == true only if all types in wList occured once, remove call to Distinct