This is an alternative way of doing it.
To remove the Max-/minimize you need to change the ResizeMode like this
<Window x:Class="MyWpfApplication.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="" Height="350" Width="525" ResizeMode="NoResize">
    <Grid>
    </Grid>
</Window>
After that you can remove the Close button by adding this ( read more here )
private const int GWL_STYLE = -16;
private const int WS_SYSMENU = 0x80000;
[DllImport("user32.dll", SetLastError = true)]
private static extern int GetWindowLong(IntPtr hWnd, int nIndex);
[DllImport("user32.dll")]
private static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
public MainWindow()
{
    SourceInitialized += Window_SourceInitialized;
}
void Window_SourceInitialized(object sender, EventArgs e)
{
    var hwnd = new WindowInteropHelper(this).Handle;
    SetWindowLong(hwnd, GWL_STYLE, GetWindowLong(hwnd, GWL_STYLE) & ~WS_SYSMENU);
}