WPF MVVM属性绑定无法正常工作

Question

我创建了一个视图模型，该模型具有一个为学生模型的单个属性，然后我将其绑定到XAML中的控件。但是当我执行应用程序时，什么都不会出现。

我正在我的app.xaml.cs中设置数据上下文，如下所示：

 protected override void OnStartup(StartupEventArgs e)   
 {         
   base.OnStartup(e);
   Registrationformusinemvvm.MainWindow window = new MainWindow();
   VMUser VM = new VMUser();
   window.DataContext = VM;
   window.Show();
 }

为什么绑定不起作用？

这是我的视图模型：

   public class VMUser:BaseClass
   {    
     private student _currentStudent;
     public student CurrentStudent
     {
         get { return _currentStudent; }
         set { 
               _currentStudent = value; 
               OnPropertyChanged("CurrentStudent");    
         }
     }
   }

我的学生模特课：

 public class student:BaseClass
 {      
   private string name="sumit";
     public string Name
     {
         get { return name; }
         set { name = value; OnPropertyChanged("Name"); }
     }
     private int rollNum;
     public int RollNum
     {
         get { return rollNum; }
         set { rollNum = value;OnPropertyChanged("RollNum"); }
     }
     private int phNum;
     public int PhNum
     {
         get { return phNum; }
         set { phNum = value;OnPropertyChanged("PhNum"); }
     }
     private string sub;
     public string Sub
     {
         get { return sub; }
         set { sub = value;OnPropertyChanged("Sub"); }
     }
 }

我的XAML：

<Window x:Class="Registrationformusinemvvm.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:Registrationformusinemvvm"
    xmlns:vm="clr-namespace:Registrationformusinemvvm.ViewModel"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="525">
  <!--<Window.DataContext>
    <vm:VMUser/>
  </Window.DataContext>-->
  <Window.Resources>
 </Window.Resources>
 <Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="50"/>
        <RowDefinition Height="50"/>
        <RowDefinition Height="50"/>
        <RowDefinition Height="50"/>
        <RowDefinition Height="50"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
        <ColumnDefinition Width="200"/>
        <ColumnDefinition Width="200"/>
        <ColumnDefinition Width="*"/>
    </Grid.ColumnDefinitions>
    <TextBlock Text="Name"  Grid.Column="0" Grid.Row="0" FontSize="14"       
    FontWeight="Bold" VerticalAlignment="Center"   
    HorizontalAlignment="Center"/>
    <TextBlock Text="Roll Number" Grid.Column="0" Grid.Row="1" FontSize="14" 
   FontWeight="Bold" VerticalAlignment="Center"   
   HorizontalAlignment="Center"/>
    <TextBlock Text="Subject" Grid.Column="0" Grid.Row="2" FontSize="14" 
  FontWeight="Bold" VerticalAlignment="Center" 
  HorizontalAlignment="Center"/>
    <TextBlock Text="Phone Number" Grid.Column="0" Grid.Row="3"  
  FontSize="14" FontWeight="Bold" VerticalAlignment="Center" 
 HorizontalAlignment="Center"/>
    <TextBox Name="tbName" Text="{Binding CurrentStudent.Name,Mode=TwoWay,   
 UpdateSourceTrigger=PropertyChanged}" Grid.Column="1" Grid.Row="0" 
Width="120" Height="30" HorizontalAlignment="Center" 
VerticalAlignment="Center"/>
    <TextBox Name="tbRollnum" Text="{Binding CurrentStudent.RollNum}" 
Grid.Column="1" Grid.Row="1" Width="120" Height="30"   
HorizontalAlignment="Center" VerticalAlignment="Center"/>
    <TextBox Name="tbSub" Text="{Binding CurrentStudent.Sub}" 
Grid.Column="1" Grid.Row="2" Width="120" Height="30" 
HorizontalAlignment="Center" VerticalAlignment="Center"/>
    <TextBox Name="tbPh" Text="{Binding CurrentStudent.PhNum}" 
Grid.Column="1" Grid.Row="3" Width="120" Height="30" 
HorizontalAlignment="Center" VerticalAlignment="Center"/>
    <Button Name="tbSubmit" Content="Submit" Grid.ColumnSpan="3" 
Grid.Row="4" Height="30" Width="100" HorizontalAlignment="Center"/>
</Grid>
</Window>

Answer 1

我的猜测是您的绑定不起作用，因为您的_currentStudent默认情况下是无效的。初始化您的_currentStudent（如果为null）。

    public student CurrentStudent
    {
        get { return _currentStudent = (_currentStudent ?? new student()); }
        set
        {
            _currentStudent = value; OnPropertyChanged("CurrentStudent");
        }
    }

Answer 2

您需要在模型类中添加onPropertychang。

void OnPropertyChanged(string prop)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(prop));
        }
        public event PropertyChangedEventHandler PropertyChanged;

Answer 3

根据您的上述代码，您无法将值分配给当前研究属性您能检查您是否有当前研究属性的价值。

谢谢您的问题

Answer 4

从 app.xaml