Wpf merged resource dictionary no being recognized from app.xaml

Question

I have a WPF .net 4.5 application where I am having trouble merging resource dictionaries.

I have the exact same problem as This SO question and This Question but th

Answer 1

In addition to @lisp answer, I have written tt template, which take all files from Default.xaml, find them and join into one file, which than we can use in app.xaml

So we can structure files, have performance, static resource will work...

<#@ template debug="false" hostspecific="true" language="C#" #>
<#@ assembly name="System.Core" #>
<#@ assembly name="System.Xml" #>
<#@ assembly name="System.Xml.Linq" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Xml.Linq" #>
<#@ import namespace="System.Text" #>
<#@ import namespace="System.IO" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ output extension=".xaml" #>

<#
    IDictionary GetNamespaces(XDocument doc)
    {
        return doc.Root.Attributes()
                    .Where(a => a.IsNamespaceDeclaration)
                    .GroupBy(a => a.Name.Namespace == XNamespace.None ? string.Empty : a.Name.LocalName, a=>XNamespace.Get(a.Value))
                    .ToDictionary(g => g.Key, g => g.First());
    }

    XDocument GetFlattenResourceDocument(string path)
    {
        var xFilePath = this.Host.ResolvePath(path);
        var doc = XDocument.Load(xFilePath);

        var defaultNs = doc.Root.GetDefaultNamespace();

        var mergedDictElement = doc.Root.Elements(defaultNs + "ResourceDictionary.MergedDictionaries").SingleOrDefault();
        if (mergedDictElement == null)
            return doc;

        var rootNamespaces = GetNamespaces(doc);

        var mergedResourceDictionaries = mergedDictElement.Elements(defaultNs + "ResourceDictionary");
        var addAfterElement = mergedDictElement as XNode;

        foreach(var resourceDict in mergedResourceDictionaries)
        {
            var sourcePath = resourceDict.Attribute("Source").Value;
            var flattenDoc = GetFlattenResourceDocument(sourcePath);

            var flatNamespaces = GetNamespaces(flattenDoc);

            foreach(var key in flatNamespaces.Keys)
            {
                if(!rootNamespaces.ContainsKey(key))
                {
                    var curNamespace = flatNamespaces[key];
                    doc.Root.Add(new XAttribute(XNamespace.Xmlns + key, curNamespace.ToString()));
                    rootNamespaces.Add(key, curNamespace);
                }
            }

            var startComment = new XComment($"Merged from file {sourcePath}");
            var endComment = new XComment($"");

            var list = new List();
            list.Add(startComment);
            list.AddRange(flattenDoc.Root.Elements());
            list.Add(endComment);
            addAfterElement.AddAfterSelf(list);

            addAfterElement = endComment;

        }

        mergedDictElement.Remove();

        return doc;
    }
#>
<#= GetFlattenResourceDocument("Default.xaml").ToString() #>