<Grid x:Name="root">
        <TextBox Text="{Binding str1}"  Width="200" Height="25" Margin="92,23.5,92,0" VerticalAlignment="Top" d:LayoutOverrides="Height"/>
        <Button IsEnabled="{Binding YN}" Margin="92,106,92,116" Content="按钮"/>
        <TextBox Text="{Binding str2}" Width="200" Height="25" Margin="92,0,92,28.5" VerticalAlignment="Bottom" d:LayoutOverrides="Height"/>
        
    </Grid>

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        void MainWindow_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            //apps.Resize(root.ActualWidth, root.ActualHeight);
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            //apps.Resize(root.ActualWidth, root.ActualWidth);
            root.DataContext = new BingO() { str1 = "qq", str2 = "ww2" };
        }
    }

    public class BingO
    {
        public string str1 { get; set; }

        public string str2 { get; set; }

        public bool YN
        {
            get
            {
                return str1.Length > str2.Length;
            }
        
        }
    }