设置一秒钟的绑定 window

Question

我有两个 WPF windows，我想将上下文设置为 ViewModel，但如果我写：

this.DataContext = new myViewModel()

在我的第二个 windows cs 中它不起作用，这是我的代码。我试图在 XAML 中放置一个绑定并连接上下文但是当我尝试调试它时我得到错误代码这个断点不会得到运行.

BrowseDialog.xaml

 <Window x:Class="TextalkApi.BrowseDialog"
        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:TextalkApi"
        mc:Ignorable="d"
        Title="BrowseDialog" Height="248.361" Width="427.459">
    <Grid>
        <Button Content="Browse" HorizontalAlignment="Left" Margin="267,11,0,0" VerticalAlignment="Top" Width="75"/>
        <TextBox x:Name="FileDialog" HorizontalAlignment="Left" Height="23" Margin="10,10,0,0" TextWrapping="Wrap" Text="{Binding webUrl}" VerticalAlignment="Top" Width="244"/>
        <Button Content="Save" HorizontalAlignment="Left" Margin="267,166,0,0" VerticalAlignment="Top" Width="75" Command="{Binding SaveCommand}" />
        <TextBox HorizontalAlignment="Left" Height="23" Margin="10,38,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
        <Label Content="{Binding errorMessage}" HorizontalAlignment="Left" Margin="10,167,0,0" VerticalAlignment="Top" RenderTransformOrigin="-5.611,10.822" Width="207" Height="19"/> 
    </Grid>
</Window>

浏览视图模型

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Input;
using System.Threading;
using System.Threading.Tasks;
using System.Configuration;
using System.Collections.Specialized;
using System.IO;

namespace Data
{
    public class BrowseViewModel : BaseViewModel
    {
        #region public variables
        public string webUrl { get; set; }
        public string errorMessage { get; set; }
        #endregion

        #region Public Commands
        public ICommand SaveCommand { get; set; }
        #endregion

        #region Constructor
        public BrowseViewModel()
        {
            this.SaveCommand = new RelayCommand(SaveFilePath);
        }
        #endregion

        #region Private methods
        private void SaveFilePath()
        {
            if (File.Exists(webUrl))
            {
                ConfigurationManager.AppSettings.Add("WebUrl", webUrl);
            }
            else
            {
                errorMessage = "Filen existerar ej"; 
            }
        }
        #endregion
    }
}

BrowseDialog.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Shapes;
using System.IO;
using Data;

namespace TextalkApi
{
    /// <summary>
    /// Interaction logic for BrowseDialog.xaml
    /// </summary>
    public partial class BrowseDialog : Window
    {
        public BrowseDialog()
        {
            InitializeComponent();
            this.DataContext = new BrowseViewModel();
        }
    }
}

BaseViewModel

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;
using PropertyChanged;

namespace Data
{
    [AddINotifyPropertyChangedInterface]

    public class BaseViewModel : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
    }
}

Answer 1

您的 XAML 看起来是正确的，我高度怀疑是 ViewModel 导致它无法工作。这样的东西应该可以工作。

请注意，这在很大程度上取决于 BaseViewModel 的实现方式。如果可能的话，您可以分享这个，以便我可以更新我的答案以使其正确吗？以下是您应该如何在 ViewModel 中实现属性，即 View 的 DataContext。

#region Properties
    private string _webUrl;
    public string WebUrl 
    { 
        get => _webUrl;     
        set 
        {
            //This will change based on how you have implemented your BaseViewModel!
            //The method name might be different, or have different parameters!
            this.SetProperty(ref _webUrl, value, nameof(WebUrl));
            //Call the save file path validation method...
            SaveFilePath();
        }
    }

    private string _errorMessage;
    public string ErrorMessage 
    { 
        get => _errorMessage;           
        private set 
        {
            //This will change based on how you have implemented your BaseViewModel!
            //This method should call NotifyPropertyChange to notify the UI to update...
            this.SetProperty(ref _errorMessage, value, nameof(ErrorMessage));
        }
    }
#endregion

在您的 ViewModelBase 中，您可以添加一个通用的 SetProperty 方法，该方法可以为您处理引发属性 changed 事件。像这样：

public class ViewModelBase : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void SetProperty<T>(ref T storage, T value, string propertyName)
    {
        storage = value;
        RaisePropertyChangedEvent(propertyName);
    }

    protected void RaisePropertyChangedEvent(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

并且由于 ViewModel 中的更改，您还需要更新 XAML 中的绑定。

<Grid>
    <Button Content="Browse" HorizontalAlignment="Left" Margin="267,11,0,0" VerticalAlignment="Top" Width="75"/>
    <TextBox x:Name="FileDialog" HorizontalAlignment="Left" Height="23" Margin="10,10,0,0" TextWrapping="Wrap" Text="{Binding WebUrl}" VerticalAlignment="Top" Width="244"/>
    <Button Content="Save" HorizontalAlignment="Left" Margin="267,166,0,0" VerticalAlignment="Top" Width="75" Command="{Binding SaveCommand}" />
    <TextBox HorizontalAlignment="Left" Height="23" Margin="10,38,0,0" TextWrapping="Wrap" VerticalAlignment="Top" Width="120"/>
    <Label Content="{Binding ErrorMessage}" HorizontalAlignment="Left" Margin="10,155,0,0" VerticalAlignment="Top" RenderTransformOrigin="-5.611,10.822" Width="207" Height="46"/>
</Grid>

设置一秒钟的绑定 window

Setting a binding for a second window

c#

mvvm

datacontext