在之前的文章中讲过如何实现撤消重做栈：https://gyrojeff.top/index.php/archives/wpf-implement-undo-redo/
问题引入
之前，我们每定义一个支持撤消重做的属性都要写很多代码：
private string _text;
public string Text
{
get => _text;
set => UndoRedoManager.PushAndPerformRecord(o =>
{
var nowValue = Text;
SetProperty(ref _text, (string)o);
return nowValue;
}, o =>
{
var nowValue = Text;
o ??= value;
SetProperty(ref _text, (string)o);
return nowValue;
});
}C
本文的目标是将上述冗长的表达改写成：
private string _text;
[Undoable]
public string Text
{
get => _text;
set => SetProperty(value);
}C
实现逻辑
代码
public enum BackingNamingStyle
{
/// <summary>
/// Example: "BackingStore" => "_backingStore"
/// </summary>
UnderscoreAndLowerCase,
/// <summary>
/// Example: "BackingStore" => "backingStore"
/// </summary>
LowerCase
}
public partial class NotifyObject
{
public bool SetProperty<T>(T value, [CallerMemberName] string propertyName = "",
BackingNamingStyle backingNamingStyle = BackingNamingStyle.UnderscoreAndLowerCase,
Action beforeChanged = null, Action onChanged = null,
UndoRedoRecord.DelegateActionWithAndReturnValue undoAction = null,
UndoRedoRecord.DelegateActionWithAndReturnValue redoAction = null,
UndoRedoRecord.DelegateActionWithValue disposeAction = null)
{
var backingName = "";
switch (backingNamingStyle)
{
case BackingNamingStyle.LowerCase:
backingName = propertyName[0].ToString().ToLower() + propertyName.Substring(1);
break;
case BackingNamingStyle.UnderscoreAndLowerCase:
backingName = "_" + propertyName[0].ToString().ToLower() + propertyName.Substring(1);
break;
}
Type type = null;
FieldInfo backingInstance = null;
do
{
type = type == null ? GetType() : type.BaseType;
if (type == null) return false;
backingInstance = type.GetField(backingName, BindingFlags.NonPublic | BindingFlags.Instance);
} while (backingInstance == null);
if (EqualityComparer<T>.Default.Equals((T)backingInstance.GetValue(this), value))
return false;
var attribute = GetType().GetProperty(propertyName)?.GetCustomAttribute<Undoable>();
if (attribute == null)
{
beforeChanged?.Invoke();
backingInstance.SetValue(this, value);
onChanged?.Invoke();
RaisePropertyChanged(propertyName);
}
else
{
UndoRedoManager.PushAndPerformRecord(undoAction ?? (o =>
{
var nowValue = backingInstance.GetValue(this);
backingInstance.SetValue(this, o);
RaisePropertyChanged(propertyName);
return nowValue;
}), redoAction ?? (o =>
{
var nowValue = backingInstance.GetValue(this);
o ??= value;
backingInstance.SetValue(this, o);
RaisePropertyChanged(propertyName);
return nowValue;
}), disposeAction);
}
return true;
}
}C
