Fallback not respected in UWP ImageSet

[almedina-ms]

Platform

• .NET HTML
• .NET WPF
• UWP
• Android
• iOS

Version of SDK

latest master

Issue

The .NET platform and the UWP renderer render this card in two different ways; there are two big differences:

1. Fallback is not being respected in UWP

{
	"$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
	"type": "AdaptiveCard",
	"version": "1.0",
	"body": [
		{
			"type": "ImageSet",
			"imageSize": "auto",
			"images": [
				{
					"type": "Image",
					"url": "http://adaptivecards.io/content/cats/1.png",
					"size": "small"
				},
				{
					"type": "Image",
					"url": "http://adaptivecards.io/content/cats/2.png",
					"size": "medium"
				},
				{
					"type": "Image",
					"url": "http://adaptivecards.io/content/cats/3.png",
					"size": "large",
					"requires": 
					{
						"adaptiveCard": "1.4"
					},
					"fallback": 
					{
						"type": "TextBlock",
						"text": "Some text"
					}
				},
				{
					"type": "Image",
					"url": "http://adaptivecards.io/content/cats/1.png",
					"backgroundColor": "#228B22"
				},
				{
					"type": "Image",
					"url": "http://adaptivecards.io/content/cats/2.png",
					"size": "stretch"
				},
				{
					"type": "Image",
					"url": "http://adaptivecards.io/content/cats/3.png",
					"style": "person"
				}
			]
		}
	]
}

[RebeccaAnne]

@almedina-ms lets split this into two separate bugs.

[shalinijoshi19]

@almedina-ms did you ever get to splitting this bug? If not can you create a separate one for tracking issue #2 (Image sizes are not being respected in UWP when ImageSet imageSize is set to auto)

[matthidinger]

@almedina-ms friendly ping about splitting this bug and we can triage them independently

[shalinijoshi19]

@RebeccaAnne this looks like a clear case of fallback needing to be respected in UWP yes? Assigning to you to see if we can come up with a proposal for this bug to discuss in the design notes meet.