While Animating windows forms to slide in, Form Appearing at wrong location
[DllImport("user32")]
        static extern bool AnimateWindow(IntPtr hwnd, int time, int flags);

//Set the Location  negative values are being returned when my dialog appears
                this.Location = new Point(LocationMainX + WidthOfMain, locationMainy + 10);

                //Animate form
                AnimateWindow(this.Handle, 750, AW_SLIDE | AW_HOR_POSITIVE);

AddForm form = new AddForm (this.DesktopLocation)
form.ShowDialog(); //I have also noticed doing form.Show(); messes with the position of dialog

AddForm form = new AddForm (this.Parent.DesktopLocation)
    form.ShowDialog();

using System.Runtime.InteropServices;

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetWindowRect(HandleRef hWnd, out RECT lpRect);

[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
  public int Left;
  public int Top;
  public int Right;
  public int Bottom;
}

RECT fromRECT;
GetWindowRect(new HandleRef(this, button1.Handle), out fromRECT);
form.Location = new Point(fromRECT.Left + (fromRECT.Right - fromRECT.Left), fromRECT.Top);
form.Show();