c# - 使用 GroupBy 消除 List 中的重复对象

Question

如何使用 GroupBy 来获得不同的点列表。我想消除重复的点。

List<_3DPoint> list_of_points = new List<_3DPoint> { ... };

public class _3DPoint
{
    public double X { get; set; }
    public double Y { get; set; }
    public double Z { get; set; }
}

Answer 1

而不是 GroupBy , 考虑实现 IEquatable<ThreeDPoint>并使用 Enumerable.Distinct .

public class ThreeDPoint : IEquatable<ThreeDPoint>
{
    public bool Equals(ThreeDPoint other)
    {
        if (ReferenceEquals(null, other)) return false;
        if (ReferenceEquals(this, other)) return true;
        return X.Equals(other.X) && Y.Equals(other.Y) && Z.Equals(other.Z);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (ReferenceEquals(this, obj)) return true;
        if (obj.GetType() != this.GetType()) return false;
        return Equals((ThreeDPoint) obj);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            var hashCode = X.GetHashCode();
            hashCode = (hashCode*397) ^ Y.GetHashCode();
            hashCode = (hashCode*397) ^ Z.GetHashCode();
            return hashCode;
        }
    }

    public static bool operator ==(ThreeDPoint left, ThreeDPoint right)
    {
        return Equals(left, right);
    }

    public static bool operator !=(ThreeDPoint left, ThreeDPoint right)
    {
        return !Equals(left, right);
    }

    public ThreeDPoint(double x, double y, double z)
    {
        X = x;
        Y = y;
        Z = z;
    }

    public double X { get; private set; }
    public double Y { get; private set; }
    public double Z { get; private set; }
}

现在做:

var points = new List<ThreeDPoint> { // Add elements };
points.Distinct();

编辑:

如果您仍然确信自己想要 GroupBy (我肯定会推荐使用 IEquatable<T> 方法)，你可以这样做:

var list = new List<ThreeDPoint> 
{ 
    new ThreeDPoint(1.0, 2.0, 3.0), 
    new ThreeDPoint(1.0, 2.0, 3.0), 
    new ThreeDPoint(2.0, 2.0, 2.0), 
    new ThreeDPoint(2.0, 2.0, 2.0) 
};

var distinctResult = list.GroupBy(x => new { x.X, x.Y, x.Z })
                         .Select(x => x.First());