在代码而不是XAML中呈现UserControl

我想使用RenderTargetBitmap将UserControl呈现为位图，而不必为其编写XAML。 当我这样做时，我得到一张空白图片，我错过了关键一步吗？

 ValTool.Controls.VideoFisheyeOverlayControl vfoc = new Controls.VideoFisheyeOverlayControl(); vfoc.Width = (int)this.VideoContainer.ActualWidth; vfoc.Height = (int)this.VideoContainer.ActualHeight; vfoc.FieldsOfView=this.FieldsOfView; vfoc.CountLines = this.CountLines; vfoc.UpdateLayout(); vfoc.InvalidateVisual(); RenderTargetBitmap visual = new RenderTargetBitmap((int)this.VideoContainer.ActualWidth, (int)this.VideoContainer.ActualHeight, 96, 96, PixelFormats.Pbgra32); visual.Render(vfoc); var finalImage = BitmapFrame.Create(visual); // Encoding the RenderBitmapTarget as a PNG file. PngBitmapEncoder png = new PngBitmapEncoder(); png.Frames.Add(BitmapFrame.Create(finalImage)); using (Stream stm = File.Create(@"new.png")) { png.Save(stm); } 

Answer 1

而不是UpdateLayout，你必须调用测量和安排来完成布局：

 var width = VideoContainer.ActualWidth; var height = VideoContainer.ActualHeight; vfoc.Measure(new Size(width, height)); vfoc.Arrange(new Rect(0, 0, width, height)); vfoc.InvalidateVisual();