WF中DependencyObject和DependencyProperty的实现

WF中DependencyObject和DependencyProperty的实现

 

DependencyProperty的Register和RegisterAttached方法，将DependencyProperty存在IDictionary中完成注册，确保相同name的DependencyProperty在一个ownerType类型中只能有一个。

DependencyObject的GetValue和SetValue的值存在IDictionary中。并预留了GetValueOverride 和SetValueOverride的处理。

 

用Reflector看了一下源码，下面是源码的片段

 

[Serializable]

public sealed class DependencyProperty : ISerializable

{

    private static IDictionary<int, DependencyProperty> dependencyProperties;

    public static DependencyProperty Register(string name, Type propertyType, Type ownerType)

    {

        return ValidateAndRegister(name, propertyType, ownerType, null, null, true);

    }

     public static DependencyProperty RegisterAttached(string name, Type propertyType, Type ownerType)

    {

        return ValidateAndRegister(name, propertyType, ownerType, null, null, false);

    }

 

    //Register和RegisterAttached调用ValidateAndRegister完成注册

    private static DependencyProperty ValidateAndRegister(string name, Type propertyType, Type ownerType, PropertyMetadata defaultMetadata, Type validatorType, bool isRegistered)

    {

        // Check ...

        // ...

 

        DependencyProperty property = new DependencyProperty(name, propertyType, ownerType, metadata, validatorType, isRegistered);

        lock (((ICollection)dependencyProperties).SyncRoot)

        {

            // 使用HashCode作为Key

            if (dependencyProperties.ContainsKey(property.GetHashCode()))

            {

                throw new InvalidOperationException(SR.GetString("Error_DPAlreadyExist", new object[] { name, ownerType.FullName }));

            }

            dependencyProperties.Add(property.GetHashCode(), property);

        }

        return property;

    }

     // HashCode由name和ownerType的HashCode生产，确保相同name和ownerType的DependencyProperty只能有一个。

    public override int GetHashCode()

    {

        return (this.name.GetHashCode() ^ this.ownerType.GetHashCode());

    }

}

 

[DesignerSerializer(typeof(DependencyObjectCodeDomSerializer), typeof(CodeDomSerializer)), DesignerSerializer(typeof(WorkflowMarkupSerializer), typeof(WorkflowMarkupSerializer))]

public abstract class DependencyObject : IComponent, IDependencyObjectAccessor, IDisposable

{

    private IDictionary<DependencyProperty, object> dependencyPropertyValues;

     public object GetValue(DependencyProperty dependencyProperty)

    {

        // Check...

        // ...

 

        PropertyMetadata defaultMetadata = dependencyProperty.DefaultMetadata;

 

        // 对GetValueOverride的处理

        if (defaultMetadata.GetValueOverride != null)

        {

            return defaultMetadata.GetValueOverride(this);

        }

        return this.GetValueCommon(dependencyProperty, defaultMetadata);

    }

     private object GetValueCommon(DependencyProperty dependencyProperty, PropertyMetadata metadata)

    {

        object boundValue;

        this.dependencyPropertyValues.TryGetValue(dependencyProperty, out boundValue);

 

        // Others...

 

        return boundValue;

    }

     public void SetValue(DependencyProperty dependencyProperty, object value)

    {

        // Check...

        // ...

 

        PropertyMetadata defaultMetadata = dependencyProperty.DefaultMetadata;

        this.SetValueCommon(dependencyProperty, value, defaultMetadata, true);

    }

     internal void SetValueCommon(DependencyProperty dependencyProperty, object value, PropertyMetadata metadata, bool shouldCallSetValueOverrideIfExists)

    {

        // Check...

        // ...

 

        // 对SetValueOverride的处理

        if (shouldCallSetValueOverrideIfExists && (metadata.SetValueOverride != null))

        {

            metadata.SetValueOverride(this, value);

        }

        else

        {

            // Others...

            if (dependencyPropertyValues.ContainsKey(dependencyProperty))

            {

                dependencyPropertyValues[dependencyProperty] = value;

            }

            else

            {

                dependencyPropertyValues.Add(dependencyProperty, value);

            }

        }

    }

}