设置启动窗体

1.修改App.xaml

App.xaml中原代码：

1 <Application x:Class="WpfApplication1.App"
2              xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
3              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
4              StartupUri="MainWindow.xaml">
5     <Application.Resources>
6          
7     </Application.Resources>
8 </Application>

修改为：

<Application x:Class="WpfApplication1.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:WpfApplication1"
             Startup="Application_Startup">
    <Application.Resources>

    </Application.Resources>
</Application>

2.修改App.xaml.cs

原代码：

namespace WpfApplication1
{
    /// <summary>
    /// App.xaml 的交互逻辑
    /// </summary>
    public partial class App : Application
    {
    }
}

修改为：

namespace WpfApplication1
{
    /// <summary>
    /// App.xaml 的交互逻辑
    /// </summary>
    public partial class App : Application
    {
        private void Application_Startup(object sender, StartupEventArgs e)
        {
            WpfApplication1.Login login = new WpfApplication1.Login();
            login.Show();
        }
    }
}

设置、切换主窗体

private void Btn_Login_Click(object sender, RoutedEventArgs e)
{
　　if (TB_UserName.Text == "123456" && TB_Password.Password == "123456")
　　{
　　　　MainWindow mainWindow = new MainWindow();
　　　　Application.Current.MainWindow = mainWindow;    //设置主窗体
　　　　this.Close();
　　　　mainWindow.Show();
　　}
}

显示主窗体

副窗体关闭、切换回主窗体：

private void ManageWindow_Closed(object sender, EventArgs e)
{
    Application.Current.MainWindow.Show();
}