https://forums.autodesk.com/t5/revit-api-forum/check-if-list-of-xyz-contains-a-xyz/td-p/11800804

comparetwopoint.cs

void Main()
{
	double x1 = 10;
	double y1 = 10;
	double z1 = 10;
	double x2 = 10;
	double y2 = 10;
	double z2 = 10;
	
	var point1 = new ComparePoint(x1,y1,z1);
	var point2 = new ComparePoint(x2,y2,z2);
	// case equal 
	var result = point1.CompareTo(point2);
	// if equal return 0
	// if less than return negative value
	// if greater than return positive value
	Console.WriteLine(result);
}

public class ComparePoint : IComparable<ComparePoint>
{
	public double x { get; }
	public double y { get; }
	public double z { get; }

	public ComparePoint(double x, double y, double z)
	{
		this.x = x;
		this.y = y;
		this.z = z;
	}

	public int CompareTo(ComparePoint other)
	{
		if (other == null) return 1;

		if (x.CompareTo(other.x) != 0)
		{
			return x.CompareTo(other.x);
		}
		else if (y.CompareTo(other.y) != 0)
		{
			return y.CompareTo(other.y);
		}
		else if (z.CompareTo(other.z) != 0)
		{
			return z.CompareTo(other.z);
		}
		else
		{
			return 0;
		}
	}
}