在MVVM Light中使用導航時，C＃綁定在WPF中不起作用

Question

我使用MVVMLight和MahApps創建Flat UI應用程序（WPF）。 我正在嘗試使導航正常工作。

一切似乎都還可以，但是在主窗口中由Frame托管的Page上的數據綁定存在問題。 我聲明要在登錄視圖中綁定LoginViewModel，但是當我嘗試單擊一個按鈕（連接到viewmodel中的RelayCommand）時，什么都沒有發生（我已經用調試器檢查了它）。

如何將頁面綁定到viewmodel的好方法？

MVVM燈光導航

這是我的Login.xaml（頁面）：

<Page x:Class="Project.View.Login"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:Project"
      xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
      mc:Ignorable="d" 
      d:DesignHeight="480" d:DesignWidth="640"
      Title="Login"
      DataContext="{Binding LoginViewModel, Source={StaticResource Locator}}">

    <Grid>
        <Button Command="{Binding GoToVote}" Content="{Binding Path=ButtonText}" HorizontalAlignment="Left" Margin="224,220,0,0" VerticalAlignment="Top" Width="75"/>
        <TextBox x:Name="textBox" HorizontalAlignment="Left" Height="23" Margin="224,320,0,0" TextWrapping="Wrap" Text="{Binding Path=ButtonText, Mode=TwoWay}" VerticalAlignment="Top" Width="120"/>
    </Grid>
</Page>

MainWindow.xaml（窗口）：

<Controls:MetroWindow x:Class="Project.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Project"
        mc:Ignorable="d"
        xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
        DataContext="{Binding MainViewModel, Source={StaticResource Locator}}"
        Title="MainWindow" Height="480" Width="640">
    <Frame Source="View/Login.xaml" x:Name="MainFrame" NavigationUIVisibility="Hidden" />
</Controls:MetroWindow>

ViewModelLocator.cs：

using Project.Tools;
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Ioc;
using Microsoft.Practices.ServiceLocation;
using System;

namespace Project.ViewModel
{
    /// <summary>
    /// This class contains static references to all the view models in the
    /// application and provides an entry point for the bindings.
    /// </summary>
    public class ViewModelLocator
    {
        /// <summary>
        /// Initializes a new instance of the ViewModelLocator class.
        /// </summary>
        public ViewModelLocator()
        {
            ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);

            ////if (ViewModelBase.IsInDesignModeStatic)
            ////{
            ////    // Create design time view services and models
            ////    SimpleIoc.Default.Register<IDataService, DesignDataService>();
            ////}
            ////else
            ////{
            ////    // Create run time view services and models
            ////    SimpleIoc.Default.Register<IDataService, DataService>();
            ////}

            SimpleIoc.Default.Register<MainViewModel>();
            SimpleIoc.Default.Register<LoginViewModel>();
            SimpleIoc.Default.Register<VoteViewModel>();

            var navigationService = new FrameNavigationService();
            navigationService.Configure("Login", new Uri("../View/Login.xaml", UriKind.Relative));
            navigationService.Configure("Vote", new Uri("../View/Vote.xaml", UriKind.Relative));

            SimpleIoc.Default.Register<IFrameNavigationService>(() => navigationService);
        }

        public MainViewModel MainViewModel
        {
            get
            {
                return ServiceLocator.Current.GetInstance<MainViewModel>();
            }
        }

        public LoginViewModel LoginViewModel
        {
            get
            {
                return ServiceLocator.Current.GetInstance<LoginViewModel>();
            }
        }

        public VoteViewModel VoteViewModel
        {
            get
            {
                return ServiceLocator.Current.GetInstance<VoteViewModel>();
            }
        }

        public static void Cleanup()
        {
            // TODO Clear the ViewModels
        }
    }
}

LoginViewModel.cs：

using Project.Tools;
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Project.ViewModel
{
    public class LoginViewModel : ViewModelNavigationBase
    {
        private string _buttonText;

        public RelayCommand GoCommand { get; private set; }

        void GoToVote()
        {
            _navigationService.NavigateTo("Vote");
        }

        public LoginViewModel(IFrameNavigationService navigationService) : base(navigationService)
        {
            GoCommand = new RelayCommand(GoToVote);
        }

        public string ButtonText
        {
            get { return _buttonText; }
            set
            {
                _buttonText = value;
            }
        }
    }
}

Answer 1

您是否嘗試過在第一個<Grid>上設置數據綁定？ 在根級別的對象上設置它可能會引起問題，因為該屬性可能是由承載頁面/窗口的控件設置的。

<Page x:Class="Project.View.Login"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:local="clr-namespace:Project"
      xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
      mc:Ignorable="d" 
      d:DesignHeight="480" d:DesignWidth="640"
      Title="Login">

    <Grid DataContext="{Binding LoginViewModel, Source={StaticResource Locator}}">
        <Button Command="{Binding GoToVote}" Content="{Binding Path=ButtonText}" HorizontalAlignment="Left" Margin="224,220,0,0" VerticalAlignment="Top" Width="75"/>
        <TextBox x:Name="textBox" HorizontalAlignment="Left" Height="23" Margin="224,320,0,0" TextWrapping="Wrap" Text="{Binding Path=ButtonText, Mode=TwoWay}" VerticalAlignment="Top" Width="120"/>
    </Grid>
</Page>

在主窗口上可能是同一件事。

（我猜您在App.xaml聲明了Locator 。）

Answer 2

嘗試更改）

使用GalaSoft.MvvmLight.Command; ->使用GalaSoft.MvvmLight.CommandWpf;

Answer 3

好，解決了

我犯了兩個可怕的錯誤（我不知道怎么做）。 首先：在我的類ViewModelNavigationBase中，我忘記了實現ViewModelBase （它是導航對象的擴展）。

第二-我將按鈕命令綁定到功能，而不是屬性（ ICommand ）。