WF中DependencyObject和DependencyProperty的實現

WF中DependencyObject和DependencyProperty的實現

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DependencyProperty的Register和RegisterAttached方法，將DependencyProperty存在IDictionary中完成注冊，確保相同name的DependencyProperty在一個ownerType類型中只能有一個。

DependencyObject的GetValue和SetValue的值存在IDictionary中。并預留了GetValueOverride 和SetValueOverride的處理。

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用Reflector看了一下源碼，下面是源碼的片段

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[Serializable]

public sealed class DependencyProperty : ISerializable

{

??? private static IDictionary<int, DependencyProperty> dependencyProperties;

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

??? {

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

??? }

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

??? {

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

??? }

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??? //Register和RegisterAttached調用ValidateAndRegister完成注冊

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

??? {

??????? // Check ...

??????? // ...

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

??????? lock (((ICollection)dependencyProperties).SyncRoot)

??????? {

??????????? // 使用HashCode作為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;

??? }

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??? // HashCode由name和ownerType的HashCode生產，確保相同name和ownerType的DependencyProperty只能有一個。

??? public override int GetHashCode()

??? {

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

??? }

}

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

public abstract class DependencyObject : IComponent, IDependencyObjectAccessor, IDisposable

{

??? private IDictionary<DependencyProperty, object> dependencyPropertyValues;

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??? public object GetValue(DependencyProperty dependencyProperty)

??? {

??????? // Check...

??????? // ...

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??????? PropertyMetadata defaultMetadata = dependencyProperty.DefaultMetadata;

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??????? // 對GetValueOverride的處理

??????? if (defaultMetadata.GetValueOverride != null)

??????? {

??????????? return defaultMetadata.GetValueOverride(this);

??????? }

??????? return this.GetValueCommon(dependencyProperty, defaultMetadata);

??? }

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??? private object GetValueCommon(DependencyProperty dependencyProperty, PropertyMetadata metadata)

??? {

??????? object boundValue;

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

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??????? // Others...

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??????? return boundValue;

??? }

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??? public void SetValue(DependencyProperty dependencyProperty, object value)

??? {

??????? // Check...

??????? // ...

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??????? PropertyMetadata defaultMetadata = dependencyProperty.DefaultMetadata;

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

??? }

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

??? {

??????? // Check...

??????? // ...

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??????? // 對SetValueOverride的處理

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

??????? {

??????????? metadata.SetValueOverride(this, value);

??????? }

??????? else

??????? {

??????????? // Others...

??????????? if (dependencyPropertyValues.ContainsKey(dependencyProperty))

??????????? {

??????????????? dependencyPropertyValues[dependencyProperty] = value;

??????????? }

??????????? else

??????????? {

??????????????? dependencyPropertyValues.Add(dependencyProperty, value);

??????????? }

??????? }

??? }

}