C#

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

public class ProcessWindowFinder {
  [DllImport("user32.dll", SetLastError = true)]
  [return: MarshalAs(UnmanagedType.Bool)]
  static extern bool EnumWindows(EnumWindowsProc callbackMethod, IntPtr state);

  [DllImport("user32.dll")]
  static extern UInt32 GetWindowThreadProcessId(
    [In] IntPtr hwnd,
    out UInt32 processId);

  delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr state);

  public void FindWindows(Process selectedProcess) {
    EnumWindows(SelectWindowsByPID, (IntPtr)selectedProcess.Id);
  }

  private bool SelectWindowsByPID(IntPtr hwnd, IntPtr state) {
    Int32 pid = state.ToInt32();
    Int32 windowPid = GetWindowPID(hwnd);
    if (pid == windowPid) {
      // Do something here,
      // e.g. raise an event to pass hwnd to subscribers
    }
    return true;
  }

  private Int32 GetWindowPID(IntPtr hwnd) {
    UInt32 PID;
    GetWindowThreadProcessId(hwnd, out PID);
    return unchecked((Int32)PID);
  }
}

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

private void button1_Click(object sender, EventArgs e)
{
    IntPtr runHandle = FindWindow((string)null, "Run");
    Debug.WriteLine(string.Format("Run window handle: {0}", runHandle.ToString()));
}

"Unable to find an entry point named 'FindWindow' in DLL 'user32.dll'."

private void btnTest_Click(object sender, EventArgs e)
        {
            Process p = Process.Start(@"c:\Windows\System32\rundll32.exe", "shell32.dll,#61");

            int timeOutCounter = 0;
            IntPtr runHandle = IntPtr.Zero;
            do
            {
                runHandle = FindWindow((string)null, "Run");
                Thread.Sleep(100);
                timeOutCounter = timeOutCounter + 1;
            } while ((runHandle == IntPtr.Zero) && (timeOutCounter < 30));
          
            if (runHandle != IntPtr.Zero)
            {
                SetWindowPos(runHandle, 0, 800, 800, 425, 235, 0X4 | 0x0040);
            }
              

           
        }

Process p = Process.Start(@"c:\Windows\System32\rundll32.exe",  "shell32.dll,#61");
ProcessWindowFinder finder = new ProcessWindowFinder();
finder.FindWindows(p);

EnumWindows(SelectWindowsByPID, (IntPtr)selectedProcess.Id);

IntPtr hwnd, IntPtr state

EnumWindows(SelectWindowsByPID, (IntPtr)selectedProcess.Id);

delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr state);

using System;
using System.Runtime.InteropServices;

/// <summary>
/// Get a list of window handles associated with a specific process ID
/// </summary>
public class ProcessWindowList2 : System.Collections.Generic.List<IntPtr> {

  [DllImport("user32.dll", SetLastError = true)]
  [return: MarshalAs(UnmanagedType.Bool)]
  private static extern bool EnumWindows(EnumWindowsProc callbackMethod, IntPtr state);

  private delegate bool EnumWindowsProc(IntPtr hWnd, IntPtr state);

  [DllImport("user32.dll")]
  private static extern UInt32 GetWindowThreadProcessId(
    [In] IntPtr hwnd,
    out UInt32 processId);

  private readonly Int32 pid;

  private static Int32 GetWindowPID(IntPtr hwnd) {
    UInt32 PID;
    GetWindowThreadProcessId(hwnd, out PID);
    return unchecked((Int32)PID);
  }

  private static Boolean SelectWindows(IntPtr hwnd, IntPtr state) {
    GCHandle gch = GCHandle.FromIntPtr(state);
    ProcessWindowList2 list = (ProcessWindowList2)gch.Target;

    Int32 windowPid = GetWindowPID(hwnd);
    if (list.pid == windowPid) {
      list.Add(hwnd);
    }
    return true;
  }

  /// <summary>
  /// Create and populate a list of window handles associated with a process
  /// </summary>
  /// <param name="processId">The process Id</param>
  public ProcessWindowList2(Int32 processId) {
    this.pid = processId;

    EnumWindowsProc callback = new EnumWindowsProc(SelectWindows);

    GCHandle gch = GCHandle.Alloc(this);
    try {
      EnumWindows(callback, GCHandle.ToIntPtr(gch));
    } finally {
      gch.Free();
    }
  }
}

Process p = Process.Start(@"c:\Windows\System32\rundll32.exe", "shell32.dll,#61");
ProcessWindowList2 hwndList = new ProcessWindowList2(p.Id);
foreach (IntPtr hwnd in hwndList) {
  // do something
}

public class BusinessLogic
{
    private MyDbContext context = new MyDbContext();

    public void BusinessFunction1()
    {
        // Don't call SaveChanges in here.
    }

    public void BusinessFunction2()
    {
        // Don't call SaveChanges in here.
    }

    public void SaveChanges()
    {
        // All changes made above will automatically be wrapped
        // in a transaction by EF.
        context.SaveChanges();
    }

    public void Dispose()
    {
        context.Dispose();
    }
}