Getting triangles using LINQ returns empty triangles

I have convert some C# code to VB.NET to get triangles using LINQ, and both code versions behave the same up to the point where the triangles are selected.

These are my results:

As one can see, a get a list of empty triangles, so I suspect that something is wrong in my Select statement.

Everything else is the same both in VB.NET and C#.

This is my VB.NET code, converted to the best of my knowledge:

    Function GetDelaunayTriangles(ByVal points As IEnumerable(Of Point)) As IEnumerable(Of Triangle)
        Dim result = New List(Of Triangle)()
        Dim rect = Cv2.BoundingRect(points)
        rect.Inflate(10, 10)
        Dim triangles As Vec6f()

        Using subdiv = New Subdiv2D(rect)

            For Each p In points
                Dim cv_p = New OpenCvSharp.Point2f(p.X, p.Y)
                subdiv.Insert(cv_p)
            Next

            triangles = subdiv.GetTriangleList()
        End Using

    Dim nRet As IEnumerable(Of Triangle) = From t In triangles Let p1 = New Point(t(0), t(1)) Let p2 = New Point(t(2), t(3)) Let p3 = New Point(t(4), t(5)) Where rect.Contains(p1) AndAlso rect.Contains(p2) AndAlso rect.Contains(p3) Select New Triangle(p1, p2, p3)

    Return nRet
End Function

And this is the original C# code which works:

    public static IEnumerable<Triangle> GetDelaunayTriangles(IEnumerable<Point> points)
    {
        var result = new List<Triangle>();

        // calculate the bounding box around the points
        var rect = Cv2.BoundingRect(points);
        rect.Inflate(10, 10);

        // the Subdiv2D class handles Delaunay triangulation
        // first we add all points, and then start triangulation
        Vec6f[] triangles;
        using (var subdiv = new Subdiv2D(rect))
        {
            foreach (var p in points)
            {
                var cv_p = new OpenCvSharp.Point2f(p.X, p.Y);
                subdiv.Insert(cv_p);
            }
            triangles = subdiv.GetTriangleList();
        }

        // return result as an enumeration of triangle structs
        return from t in triangles
               let p1 = new Point(t[0], t[1])
               let p2 = new Point(t[2], t[3])
               let p3 = new Point(t[4], t[5])
               where rect.Contains(p1) && rect.Contains(p2) && rect.Contains(p3)
               select new Triangle(p1, p2, p3);
    }

Thank you very much!

Edit:

I have printed the "triangles", and they are exactely the same for both VB.NET and C#. I just don't understand what I'm doing wrong in the Select statement.

Edit:

I have added a screenshot that shows that VS think that "Imports System.Linq" can be removed, which I think is not right.

Edit: Would anybody be so nice and tell me what this LINQ expression would look like in hard code (no more Linq)?