How to handle multiple process windows at the same time

Question

sorry I'm Vietnamese and use Google translate to write in English, so everyone can help answer the question I mentioned, I'm stuck on the problem of handling the process window:

here is my code:

string[] HandleParts = {"MyWindow1","MyWindow2","MyWindow3","etc.."}
while (flag)
{
    var s = new FindData()
    {
       ClassName = "#32770",
       WindowName = string.Join(@" ", HandleParts)
    };
    EnumWindows(EnumProc, ref s);
    var result = s.Result.FirstOrDefault();
    if (result != InPtr.Zero)
    {
          EnumAllChilds(result, InPtr.Zero);
          GetForegroundWindow((int)result).ToInt32();
          PostMessage(result, 0x0, 0, 0);
    }
    else
    {
            Console.WriteLine("WindowHandle Not Found!");
            break;
    }
}

I don't understand why it only works with the first 1 window in the listed list, I need help to fix the problem.