无法在对象'Identity'上设置属性，因为它处于只读状态

I am getting a eroor from my code, i cant trace the issue/bug . here is my code bit...

我从我的代码中得到了一个eroor,我无法追踪问题/错误。这是我的代码位...

private void DoArrange()
    {
        Point center = new Point((this.Width - ItemSize) / 2, (this.Height - ItemSize) / 2);
        double radiusX = center.X;
        double radiusY = center.Y;
        double scale = ScalePerspective;

        for (int i = 0; i < Children.Count; i++)
        {
            UIElement item = Children[i];
            double radians = (double)item.GetValue(CarouselPanel.AngleProperty);

            Point p = new Point(
                                (Math.Cos(radians) * radiusX) + center.X,
                                (Math.Sin(radians) * radiusY) + center.Y
                               );

            if (item.RenderTransform == null)
            {
                item.RenderTransform = new MatrixTransform();
                item.RenderTransformOrigin = new Point(0.5, 0.5);
            }
            MatrixTransform mt = item.RenderTransform as MatrixTransform;
            double scaleMinusRounding = p.Y / (center.Y + radiusY);
            double scaleX = Math.Min(scaleMinusRounding + scale, 1.0);
            double scaleY = Math.Min(scaleMinusRounding + scale, 1.0);
            Matrix mx = new Matrix(scaleX, 0.0, 0.0, scaleY, 0.0, 0.0);

            *** mt.Matrix = mx; ***

            item.RenderTransform = mt;

            int zIndex = (int)((p.Y / base.Height) * 50);
            item.SetValue(Canvas.ZIndexProperty, zIndex);
            Rect r = new Rect(p.X, p.Y, ItemSize, ItemSize);
            item.Arrange(r);
        }
    }

I edited the post again,..the error raised from the*** mt.Matrix = mx; *** statement..

我再次编辑了帖子,.. *** mt.Matrix = mx引发的错误; ***声明..

What could be the issue i am using a WPF(win) application.

可能是我使用WPF(win)应用程序的问题。

2 个解决方案

#1

Instead of assigning to the read-only matrix property, try this:

尝试这样做,而不是分配给只读的矩阵属性:

item.RenderTransform = new MatrixTransform(mx);

#2

The RenderTransform property of UIElement is initially assigned as a MatrixTransform instance whose IsSealed and IsFrozen properties are both true, instead of a null reference. It should be noticed.

UIElement的RenderTransform属性最初被指定为MatrixTransform实例,其IsSealed和IsFrozen属性都为true,而不是null引用。应该注意到。

#1