C# 在windows应用商店应用程序中设置画布子项

我在xaml中创建了两个画布，如下所示：

<Grid>
<Canvas x:Name="canvas2"    Grid.Row="0" Grid.Column="1"  Grid.ColumnSpan="11" Grid.RowSpan="8" Background="White"  >
</Canvas>
<Canvas x:Name="canvas1" RightTapped="canvas1_RightTapped"  Grid.Row="0" Grid.Column="1"  Grid.ColumnSpan="11" Grid.RowSpan="8" Background="Transparent"  >
</Canvas>
</Grid>

Canvas canvas1d = new Canvas();
canvas1d.Height = canvas1.ActualHeight; 
canvas1d.Width = canvas1.ActualWidth; 
canvas1d = canvas1;
Canvas canvas2d = new Canvas();
canvas2d.Height = canvas1.ActualHeight;
canvas2d.Width = canvas1.ActualWidth;
canvas2d = canvas2;
Canvas canvas = new Canvas();
canvas.Height = canvas1.ActualHeight; 
canvas.Width = canvas1.ActualWidth;
canvas.Children.Add(canvas2d);
canvas.Children.Add(canvas1d);

但这是一个错误

An exception of type 'System.Exception' occurred in mscorlib.dll but was not handled in user code.Element is already the child of another element

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请帮助并更正此代码。

为什么要执行

canvas1d=canvas1和
canvas2=canvas2？创建2个新的
Canvas
，然后通过使用现有元素覆盖变量来完全忽略它们。实际上，我想将canvas1和canvas2设置为Canvas的子级：
Canvas Canvas=new Canvas（）；canvas.Height=canvas1.ActualHeight；canvas.Width=canvas1.ActualWidth；canvas.Children.Add（canvas2）；canvas.Children.Add（canvas1）
但给出了相同的错误：
在mscorlib.dll中发生了类型为“System.exception”的异常，但未在用户代码中处理。元素已经是另一个元素的子元素
您在哪里声明
canvas1
和
canvas2
？你是想把它们换过来吗？即
canvas1=canvas1d？