This code gives you the list of projects which are in the open solution in visual studio.

projectList.cs

string slnPath = Directory.GetParent(Assembly.GetExecutingAssembly().Location).Parent.Parent.Parent.FullName;
List<string> projects = new List<string>();
foreach (string f in Directory.GetFiles(slnPath))
{
    if (f.Contains(".sln"))
    {
        string[] arr = System.IO.File.ReadAllLines(f);
        for (int i = 0; i < arr.Length; i++)
        {
            if (arr[i].StartsWith("Project"))
            {
                string[] temp = arr[i].Split(',');
                projects.Add(temp[1]);
            }
        }
    }
}