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我有一個關於WPF MVVM是如何工作並有工作代碼的問題，但不知道爲什麼它可以工作。大多數在線教程似乎都給出了使用單個窗口的示例，因此我不確定是否使用多個窗口/頁面/用戶控件正確執行此操作。如何在多個Windows/Pages/Controls上設置DataContext？
如果我有一個類名爲ViewModel和我使用下面的代碼設置DataContext在MainWindow，然後我設置只有MainWindow的DataContext。
MainWindow.xaml.cs：
public partial class MainWindow
{
Private ViewModel viewModel = new ViewModel();
public MainWindow()
{
InitializeComponent();
this.DataContext = this.viewModel;
}
}
如果我再創建一個新的用戶控件，然後綁定一個DataGrid但沒有指定視圖模型的路徑，爲什麼下面的工作代碼的時候我還沒有設置usercontrol的DataContext？
這是WPF的工作原理，還是我應該在usercontrol中設置DataContext？什麼是正確的方法來做到這一點？
MainSignals.xaml：
<UserControl x:Class="ProjectXYZ.Content.MainSignals"
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:core="clr-namespace:System;assembly=mscorlib"
xmlns:local="clr-namespace:ProjectXYZ.Content"
xmlns:mui="http://firstfloorsoftware.com/ModernUI"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300" >
<Grid>
<DockPanel>
<DataGrid Name="DG1" ItemsSource="{Binding ReceivedSignals}" >
<DataGrid.Columns>
<mui:DataGridTextColumn Header="SignalID" Binding="{Binding signalID}"/>
<mui:DataGridTextColumn Header="SignalType" Binding="{Binding signalType}"/>
</DataGrid.Columns>
</DataGrid>
</DockPanel>
</Grid>
</UserControl>
ViewModel.cs：
private ObservableCollection<MainWindow.SignalVar> _receivedSignals;
Public ViewModel()
{
}
public event PropertyChangedEventHandler PropertyChanged;
// Create the OnPropertyChanged method to raise the event
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}
public ObservableCollection<MainWindow.SignalVar> ReceivedSignals
{
get { return _receivedSignals; }
set
{
if (value != _receivedSignals)
{
_receivedSignals = value;
OnPropertyChanged("ReceivedSignals");
}
}
}
UserControl.xaml.cs：
public partial class MainSignals : UserControl
{
public MainSignals()
{
InitializeComponent();
//this.DataContext = new ViewModel(); //WORKS WITHOUT THIS??
}
}