Enumerate projects in a solution

DumpProjects.cs

using System;
using System.Collections.Generic;
using EnvDTE;

public class Tests
{
    [STAThread]
    static IList<string> DumpProjects(DTE dte)
    {
        var projects = new List<string>();
        foreach (Project project in dte.Solution)
        {
            AddProject(project);
        }

        void AddProject(Project project)
        {
            switch (project.Kind)
            {
                case "{66A26720-8FB5-11D2-AA7E-00C04F688DDE}":
                    // EnvDTE80.ProjectKinds.vsProjectKindSolutionFolder
                    AddSolutionFolder(project);
                    break;
                default:
                    projects.Add(project.FileName);
                    break;
            }
        }

        void AddSolutionFolder(Project project)
        {
            foreach (ProjectItem item in project.ProjectItems)
            {
                if (item.Object is Project child)
                {
                    AddProject(child);
                }
            }
        }

        return projects;
    }
}