I have a method SetImagePDF in my application that is supposed to render a Grid into a RenderTargetBitmap and convert it into an iText Image for PDF generation. However, I’m encountering an error at the line await renderTargetBitmap.RenderAsync(Page, (int)(scaledWidth), (int)(scaledHeight)); which throws an exception: ‘Value does not fall within the expected range.’

I suspect this error occurs because the Grid (Page) is never visually displayed, so RenderTargetBitmap cannot render it properly.

Here’s the part of my code:

private async Task<iText.Layout.Element.Image> SetImagePDF(Grid Page)
{
    // Crée un flux en mémoire pour stocker les images
    var stream = new InMemoryRandomAccessStream();
    RenderTargetBitmap renderTargetBitmap = new RenderTargetBitmap();
    try
    {
        int DPI = 600;
        double scaledWhidth = (210 * DPI) / 25.4;
        double scaledHeigh = (297 * DPI) / 25.4;
        await renderTargetBitmap.RenderAsync(Page, (int)(scaledWhidth), (int)(scaledHeigh));
        IBuffer pixelBuffer = await renderTargetBitmap.GetPixelsAsync();
        byte[] pixels = pixelBuffer.ToArray();
        var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, stream);
        encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied,
                                (uint)renderTargetBitmap.PixelWidth,
                                (uint)renderTargetBitmap.PixelHeight,
                                DPI, DPI, pixels);
        await encoder.FlushAsync();
        var bitmapImage = new BitmapImage();
        stream.Seek(0);
        var imageBytes = new byte[stream.Size];
        await stream.AsStream().ReadAsync(imageBytes, 0, imageBytes.Length);
        ImageData imageData = ImageDataFactory.Create(imageBytes);
        return new iText.Layout.Element.Image(imageData);
    }
    catch (Exception e) { return null; }
}

Can someone help me understand how to properly render the Grid (Page) even if it’s not visually displayed? Or suggest how to ensure RenderTargetBitmap can render it correctly?