How to unroll a recursive structure and return as IEnumerable

ienumerable_urnoll_recursive_structure.md

TODO: solution using Stack

stackoverflow questions:

How to “unroll” a “recursive” structure

IEnumerable and Recursion using yield return

My considerations

Same function in two versions. The function goes through all the elements recursively and return they as IEnumerable.

There is no solution yet, using Stack

public class ResourceFileInfo
{
    ...
    // By yield  
    public IEnumerable<ResourceInfo> GetAllResources1()
    {
        if (_localResources != null)
        {
            foreach (ResourceInfo ri in _localResources)
            {
                yield return ri;
            }
        }

        if (_mergedFiles != null)
        {
            foreach (ResourceFileInfo file in _mergedFiles)
            {
                foreach (ResourceInfo fri in file.Resources)
                {
                    yield return fri;
                }
            }
        }
    }
    
    // By Concat & SelectMany
    public IEnumerable<ResourceInfo> GetAllResources2
    {
        if (_localResources != null)
        {
            if (_mergedFiles != null)
                return _localResources.Concat(_mergedFiles.SelectMany(x => x.Resources));
            else
                return _localResources;
        }
        else
        {
            if (_mergedFiles != null)
                return _mergedFiles.SelectMany(x => x.Resources);
            else
                return Enumerable.Empty<ResourceInfo>();
        }
    }
}

Object structure:

• 📁 ResourceFileInfo
  • 📁 ResourceFileInfo
    • 📦 ResourceInfo
    • 📦 ResourceInfo
  • 📁 ResourceFileInfo
    • 📁 ResourceFileInfo
      • 📦 ResourceInfo
    • 📦 ResourceInfo
  • 📦 ResourceInfo

public class ResourceInfo
{
    public string ClassName { get; }
    public string XKey { get; }

    public ResourceInfo(string className, string xKey)
    {
        ClassName = className;  
        XKey = xKey;
    }
}

public class ResourceFileInfo
{
    internal ResourceFileInfo[] _mergedFiles;
    internal ResourceInfo[] _localResources;

    public string Path { get; }

    public IEnumerable<ResourceFileInfo> MergedFiles
        => _mergedFiles ?? Enumerable.Empty<ResourceFileInfo>();

    public IEnumerable<ResourceInfo> LocalResources
        => _localResources ?? Enumerable.Empty<ResourceInfo>();

    public ResourceFileInfo(AssemblyInfo parentAssembly, string path)
    {
        ParentAssembly = parentAssembly;
        Path = path;
    } 
    ...
}