C# Dropdown

Revit
6

I figured it out now. It is important that the BuildOutputAst is able to return a null node, in case the SelectedIndex is -1. Also had to make constructor public (Can’t understand how I missed it earlier :smiley: ). This is the code that works:

public class DummyDropdown : DSDropDownBase
{
    public DummyDropdown() : base("Name of the output") { }

    protected override SelectionState PopulateItemsCore(string currentSelection)
    {
        Items.Clear();
        Dictionary<string, int> dropdownItems = new Dictionary<string, int> {
            { "Test1", 1 },
            { "Test2", 2 },
            { "Test3", 3 },
            { "Test4", 4 },
        };
        foreach (KeyValuePair<string, int> item in dropdownItems)
        {
            Items.Add(new DynamoDropDownItem(item.Key, item.Value));
        }
        return SelectionState.Restore;
    }

    public override IEnumerable<AssociativeNode> BuildOutputAst(List<AssociativeNode> inputAstNodes )
    {
        if (Items.Count == 0 ||
            SelectedIndex == -1) //NB! This line is crucial for some reason
        {
            return new[] { AstFactory.BuildAssignment(GetAstIdentifierForOutputIndex(0), AstFactory.BuildNullNode()) };
        }

        var intNode = AstFactory.BuildIntNode((int)Items[SelectedIndex].Item);
        var assign = AstFactory.BuildAssignment(GetAstIdentifierForOutputIndex(0), intNode);
        return new List<AssociativeNode> { assign };
    }
}
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