使用されている UI フレームワークと緊密に結合されたバインディングが多数サポートされていますが、独自のバインディング フレームワークを簡単に作成することもできます。
以下は、2 つのオブジェクトのプロパティ間の一方向バインディングを実装する POC です。
注: これは考えられる方法の 1 つにすぎません。せいぜい POC (高パフォーマンス/実稼働シナリオでは微調整が必要な場合があります) であり、.Net 2.0 クラスとインターフェイスを UI フレームワーク (「バニラ」.netあなたの言葉でフレームワーク:))。これを理解したら、これを簡単に拡張して双方向バインディングもサポートできます。
class Program
{
public static void Main()
{
Source src = new Source();
Destination dst = new Destination(src);
dst.Name = "Destination";
dst.MyValue = -100;
src.Value = 50; //changes MyValue as well
src.Value = 45; //changes MyValue as well
Console.ReadLine();
}
}
//A way to provide source property to destination property
//mapping to the binding engine. Any other way can be used as well
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
internal class BindToAttribute : Attribute
{
public string PropertyName
{
get;
private set;
}
//Allows binding of different properties to different sources
public int SourceId
{
get;
private set;
}
public BindToAttribute(string propertyName, int sourceId)
{
PropertyName = propertyName;
SourceId = sourceId;
}
}
//INotifyPropertyChanged, so that binding engine knows when source gets updated
internal class Source : INotifyPropertyChanged
{
private int _value;
public int Value
{
get
{
return _value;
}
set
{
if (_value != value)
{
_value = value;
Console.WriteLine("Value is now: " + _value);
OnPropertyChanged("Value");
}
}
}
void OnPropertyChanged(string propertyName)
{
var handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
internal class Destination
{
private BindingEngine<Destination> _binder;
private int _myValue;
[BindTo("Value", 1)]
public int MyValue
{
get
{
return _myValue;
}
set
{
_myValue = value;
Console.WriteLine("My Value is now: " + _myValue);
}
}
//No mapping defined for this property, hence it is not bound
private string _name;
public string Name
{
get
{
return _name;
}
set
{
_name = value;
Console.WriteLine("Name is now: " + _name);
}
}
public Destination(Source src)
{
//Binder for Source no 1
_binder = new BindingEngine<Destination>(this, src, 1);
}
}
internal class BindingEngine<T>
{
private readonly T _destination;
private readonly PropertyDescriptorCollection _sourceProperties;
private readonly Dictionary<string, PropertyDescriptor> _srcToDestMapping;
public BindingEngine(T destination, INotifyPropertyChanged source, int srcId)
{
_destination = destination;
//Get a list of destination properties
PropertyDescriptorCollection destinationProperties = TypeDescriptor.GetProperties(destination);
//Get a list of source properties
_sourceProperties = TypeDescriptor.GetProperties(source);
//This is the source property to destination property mapping
_srcToDestMapping = new Dictionary<string, PropertyDescriptor>();
//listen for INotifyPropertyChanged event on the source
source.PropertyChanged += SourcePropertyChanged;
foreach (PropertyDescriptor property in destinationProperties)
{
//Prepare the mapping.
//Add those properties for which binding has been defined
var attribute = (BindToAttribute)property.Attributes[typeof(BindToAttribute)];
if (attribute != null && attribute.SourceId == srcId)
{
_srcToDestMapping[attribute.PropertyName] = property;
}
}
}
void SourcePropertyChanged(object sender, PropertyChangedEventArgs args)
{
if (_srcToDestMapping.ContainsKey(args.PropertyName))
{
//Get the destination property from mapping and update it
_srcToDestMapping[args.PropertyName].SetValue(_destination, _sourceProperties[args.PropertyName].GetValue(sender));
}
}
}
