stackoverflow_sample1.cs

var card = new AdaptiveCard();

try
{
    card = new AdaptiveCard(new AdaptiveSchemaVersion(1, 0))
    {
        Body =
        {
            new AdaptiveTextBlock("My Holiday List - " + userCity),
            new AdaptiveTextBlock("Please select city:"),

            new AdaptiveChoiceSetInput
            {
                Choices = list,
                Id = "CountryOrganizationCode",
                Style = AdaptiveChoiceInputStyle.Compact,
                Value = "Delhi",
                // IsMultiSelect = false,
            },
        },
    };

    card.Actions = new List<AdaptiveAction>
    {
        new AdaptiveShowCardAction
        {
            Title = "View Holiday List ",
            Type =  "Action.ShowCard",
            Card = new AdaptiveCard(new AdaptiveSchemaVersion(1, 0))
            {
                Body =
                {
                    new AdaptiveTextBlock()
                    {
                        Text = holidaylist.Where(i => i.Key == ((AdaptiveCards.AdaptiveChoiceSetInput)card.Body[2]).Value).FirstOrDefault().Value.ToString(),
                        Wrap = true,
                    },
                },
            },
        },
    };
}