Finding all Images in a FlowDocument

Question

Since I am pretty new to WPF FlowDocuments I would like to ask if the code below is correct. It is supposed to return all Images contained in a FlowDocument as List:

Answer 1

Little change in Code to add coverage for Figure and Floater

public static IEnumerable FindImages(FlowDocument document)
    {
        return document.Blocks.SelectMany(block => FindImages(block));
    }        

    public static IEnumerable FindImages(Block block)
    {
        if (block is Paragraph)
        {
            List toReturn = new List();
            var check = ((Paragraph)block).Inlines;
            foreach (var i in check)
            {
                if (i is InlineUIContainer)
                {
                    var inlineUiContainer = i as InlineUIContainer;
                    Image image = ((InlineUIContainer)inlineUiContainer).Child as Image;
                    if(image != null)
                    {
                        toReturn.Add(image);
                    }
                }
                else if (i is Figure)
                {
                    var figure = i as Figure;
                    var images = figure.Blocks.SelectMany(blocks => FindImages(blocks));
                    toReturn.AddRange(images);
                }
                else if (i is Floater)
                {
                    var floater = i as Floater;
                    var images = floater.Blocks.SelectMany(blocks => FindImages(blocks));
                    toReturn.AddRange(images);
                }
            }
            return toReturn;               
        }
        if (block is Table)
        {
            return ((Table)block).RowGroups
                .SelectMany(x => x.Rows)
                .SelectMany(x => x.Cells)
                .SelectMany(x => x.Blocks)
                .SelectMany(innerBlock => FindImages(innerBlock));
        }            
        if (block is BlockUIContainer)
        {
            Image i = ((BlockUIContainer)block).Child as Image;
            return i == null
                        ? new List()
                        : new List(new[] { i });
        }
        if (block is List)
        {
            return ((List)block).ListItems.SelectMany(listItem => listItem
                                                                  .Blocks
                                                                  .SelectMany(innerBlock => FindImages(innerBlock)));
        }
        throw new InvalidOperationException("Unknown block type: " + block.GetType());
    }