C# RenderTargetBitmap RenderAsync值不在预期范围内

使用本指南：

我以为这是在公园里散步，直到我在这一部分中发现了错误：

await renderTargetBitmap.RenderAsync(grid_editor);

这是我的XAML

<Grid Name="grid_editor" Width="500" Height="500">
                        <Image x:Name="image_snap_preview" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Source="Assets/login/images/image (1).JPG"/>
                        <TextBlock Name="txt_123" Text="This text is on top of the image" FontSize="40" TextWrapping="Wrap" Margin="70"/>
                    </Grid>

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加载网格后需要调用您的代码。与

RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
            await renderTargetBitmap.RenderAsync(grid_editor);

            image_preview.Source = renderTargetBitmap;