[英]How to create a TwoWay data-binding proxy?
我有以下课程......
class ExpressionBinder<T>
{
public Func<T> Getter;
public Action<T> Setter;
public T Value
{
get { return Getter.Invoke(); }
set { Setter.Invoke(value); }
}
public ExpressionBinder(Func<T> getter, Action<T> setter)
{
Getter = getter;
Setter = setter;
}
}
class ComparisonBinder<TSource, TValue> : ExpressionBinder<bool>, INotifyPropertyChanged
{
private TSource instance;
private TValue comparisonValue;
private PropertyInfo pInfo;
public event PropertyChangedEventHandler PropertyChanged;
public ComparisonBinder(TSource instance, Expression<Func<TSource, TValue>> property, TValue comparisonValue) : base(null,null)
{
pInfo = GetPropertyInfo(property);
this.instance = instance;
this.comparisonValue = comparisonValue;
Getter = GetValue;
Setter = SetValue;
}
private bool GetValue()
{
return comparisonValue.Equals(pInfo.GetValue(instance, null));
}
private void SetValue(bool value)
{
if (value)
{
pInfo.SetValue(instance, comparisonValue,null);
NotifyPropertyChanged("CustomerName");
}
}
private void NotifyPropertyChanged(string pName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(pName));
}
}
/// <summary>
/// Adapted from surfen's answer (https://stackoverflow.com/a/10003320/219838)
/// </summary>
private PropertyInfo GetPropertyInfo(Expression<Func<TSource, TValue>> propertyLambda)
{
Type type = typeof(TSource);
MemberExpression member = propertyLambda.Body as MemberExpression;
if (member == null)
throw new ArgumentException(string.Format(
"Expression '{0}' refers to a method, not a property.",
propertyLambda));
PropertyInfo propInfo = member.Member as PropertyInfo;
if (propInfo == null)
throw new ArgumentException(string.Format(
"Expression '{0}' refers to a field, not a property.",
propertyLambda));
if (type != propInfo.ReflectedType &&
!type.IsSubclassOf(propInfo.ReflectedType))
throw new ArgumentException(string.Format(
"Expresion '{0}' refers to a property that is not from type {1}.",
propertyLambda,
type));
return propInfo;
}
}
我使用ComparisonBinder
class 的代码如下:
radioMale.DataBindings.Add(
"Checked",
new ComparisonBinder<DataClass, GenderEnum>(DataObj, (x) => x.Gender, GenderEnum.Male),
"Value",
false,
DataSourceUpdateMode.OnPropertyChanged);
radioFemale.DataBindings.Add(
"Checked",
new ComparisonBinder<DataClass, GenderEnum>(DataObj, (x) => x.Gender, GenderEnum.Male),
"Value",
false,
DataSourceUpdateMode.OnPropertyChanged);
它们允许我使用表达式将许多控件绑定到同一属性,从而为控件的绑定属性生成值。 从控件到 object,它工作得很好。(如果你想了解更多关于使用这个 class 和这个问题的信息)
现在,我需要换个方向。 当我更新我的 object(这将改变 get 表达式的结果)时,我需要更新绑定控件。 我尝试实施INotifyPropertyChanged
但它没有任何区别。
一件奇怪的事情:将控件DataSourceUpdateMode
设置为OnPropertyChanged
以某种方式阻止我更改选中的无线电。
((PropertyChangedEventArgs) args).PropertyName == pInfo.Name
时引发BindSource.DataSource
BindingSource
将控件绑定到数据对象的属性可用(连同其他绑定类)位于: http://github.com/svallory/BindingTools
class ExpressionBinder<T> : INotifyPropertyChanged
{
public Func<T> Getter;
public Action<T> Setter;
public event PropertyChangedEventHandler PropertyChanged;
protected IList<string> WatchingProps;
public T Value
{
get { return Getter.Invoke(); }
set { Setter.Invoke(value); }
}
public ExpressionBinder(Func<T> getter, Action<T> setter)
{
WatchingProps = new List<string>();
Getter = getter;
Setter = setter;
}
public ExpressionBinder(Func<T> getter, Action<T> setter, ref PropertyChangedEventHandler listenToChanges, IList<string> propertyNames)
{
Getter = getter;
Setter = setter;
listenToChanges += SourcePropertyChanged;
WatchingProps = propertyNames;
}
protected void SourcePropertyChanged(object obj, PropertyChangedEventArgs args)
{
if (PropertyChanged != null && WatchingProps.Contains(args.PropertyName))
{
PropertyChanged(this, args);
}
}
protected PropertyInfo GetPropertyInfo<TSource, TValue>(Expression<Func<TSource, TValue>> propertyLambda)
{
Type type = typeof(TSource);
var member = propertyLambda.Body as MemberExpression;
if (member == null)
throw new ArgumentException(string.Format(
"Expression '{0}' refers to a method, not a property.",
propertyLambda));
var propInfo = member.Member as PropertyInfo;
if (propInfo == null)
throw new ArgumentException(string.Format(
"Expression '{0}' refers to a field, not a property.",
propertyLambda));
if (type != propInfo.ReflectedType &&
!type.IsSubclassOf(propInfo.ReflectedType))
throw new ArgumentException(string.Format(
"Expresion '{0}' refers to a property that is not from type {1}.",
propertyLambda,
type));
return propInfo;
}
}
class ComparisonBinder<TSource, TValue> : ExpressionBinder<bool> where TSource : INotifyPropertyChanged
{
private readonly TSource instance;
private readonly TValue comparisonValue;
private readonly PropertyInfo pInfo;
public ComparisonBinder(TSource instance, Expression<Func<TSource, TValue>> property, TValue comparisonValue)
: base(null, null)
{
pInfo = GetPropertyInfo(property);
this.instance = instance;
this.comparisonValue = comparisonValue;
Getter = GetValue;
Setter = SetValue;
instance.PropertyChanged += SourcePropertyChanged;
WatchingProps.Add(pInfo.Name);
}
private bool GetValue()
{
return comparisonValue.Equals(pInfo.GetValue(instance, null));
}
private void SetValue(bool value)
{
if (value)
{
pInfo.SetValue(instance, comparisonValue, null);
}
}
}
var bs = new BindingSource();
bs.DataSource = new ComparisonBinder<MySourceObjClass, PropType>(
MySourceObject,
p => p.PropertyToBind,
ValueToCompare);
rdBeSmart.DataBindings.Add(
"Checked",
bs,
"Value");
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