我想要从我在用户控件中使用的视图模型中更新primaryviewmodel中的属性。

// 用户控件的视图模型
public class UserControlViewModel : INotifyPropertyChanged
{
    private string _userInput;
    public string UserInput
    {
        get { return _userInput; }
        set
        {
            if (_userInput != value)
            {
                _userInput = value;
                OnPropertyChanged(nameof(UserInput));
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

// primaryviewmodel
public class PrimaryViewModel : INotifyPropertyChanged
{
    private string _updatedProperty;
    public string UpdatedProperty
    {
        get { return _updatedProperty; }
        set
        {
            if (_updatedProperty != value)
            {
                _updatedProperty = value;
                OnPropertyChanged(nameof(UpdatedProperty));
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

// 在用户控件中使用视图模型
<UserControl>
    <Grid>
        <TextBox Text="{Binding UserInput, Mode=TwoWay}" />
    </Grid>
</UserControl>

// 在主页面中使用用户控件和primaryviewmodel
<Grid>
    <local:UserControlName />
    <TextBlock Text="{Binding UpdatedProperty}" />
</Grid>