I'm trying to add background image into Adaptive card. Currently I'm using adaptive card version 1.2 , I have added the image into a folder inside the project. But I'm getting `Could not determine JSON object type for type AdaptiveCards.AdaptiveBackgroundImage` exception.

```
 Uri uri = new System.Uri(@"~\Images\AdaptiveCard_Background.png",UriKind.Relative);
 card.Add(new AdaptiveBackgroundImage() 
 {
    Url = uri
 });

```

Kindly help me in resolving this issue