当视图模型的往返更改实际值时，WPF TextBox内容不会更新

Question

我有下面的WPF文本框：

<TextBox Grid.Column="0"
Grid.Row="1" 
Text="{Binding myPath, UpdateSourceTrigger=PropertyChanged}"                 
Margin="5,8,8,5" /> 

它在视图模型中的属性是：

public string myPath
{
get => myObject.path;
set
{
// Do some comprobations before assigning the new value
if (comprobationsOk(value))
{
Uri myUri = new Uri(value);
myObject.path = myUri.LocalPath;
this.OnPropertyChanged();
}
}
}

这是ViewModelBase类中的OnPropertyChanged方法，它实现了INotifyPropertyChanged:

protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

正如您所看到的，实际的视图模型值在setter中进行了转换。

当用户开始在TextBox///my/absolute/path中键入时，视图模型中的属性将获得//my/absolute/path
所以我希望TextBox更新为//my/absolute/path，但它不是，并且保持为///my/absolute/path

Answer 1

实际上，它与工作视图模型配合得很好。

视图：

<TextBox Text="{Binding Path, UpdateSourceTrigger=PropertyChanged}" />

查看模型：

public class ViewModel : NotifyPropertyChangedBase
{
private string _name = string.Empty;
public string Path
{
get => _name;
set
{
// To avoid constant System.UriFormatException, we use the try method
var newValue = Uri.TryCreate(value, UriKind.Absolute, out var result) ? result.LocalPath : value;
Update(ref _name, newValue);
}
}
}

NotifyPropertyChangedBase:

public abstract class NotifyPropertyChangedBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler? PropertyChanged;
protected void Update<T>(ref T field, T newValue, [CallerMemberName] string? propertyName = null)
{
if (Equals(field, newValue))
return;
field = newValue;
OnPropertyChanged(propertyName);
}
protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}