DynamicObject 类

定义

public ref class DynamicObject : System::Dynamic::IDynamicMetaObjectProvider

public class DynamicObject : System.Dynamic.IDynamicMetaObjectProvider

[System.Diagnostics.CodeAnalysis.RequiresDynamicCode("Creating a call site may require dynamic code generation.")]
public class DynamicObject : System.Dynamic.IDynamicMetaObjectProvider

[System.Serializable]
public class DynamicObject : System.Dynamic.IDynamicMetaObjectProvider

type DynamicObject = class
    interface IDynamicMetaObjectProvider

[<System.Diagnostics.CodeAnalysis.RequiresDynamicCode("Creating a call site may require dynamic code generation.")>]
type DynamicObject = class
    interface IDynamicMetaObjectProvider

[<System.Serializable>]
type DynamicObject = class
    interface IDynamicMetaObjectProvider

Public Class DynamicObject
Implements IDynamicMetaObjectProvider

继承

Object

DynamicObject

派生

System.Windows.Interop.DynamicScriptObject

属性

RequiresDynamicCodeAttribute SerializableAttribute

实现

IDynamicMetaObjectProvider

示例

假设你想要提供用于访问字典中的值的替代语法，以便无需在 Visual Basic 中编写 sampleDictionary["Text"] = "Sample text" （sampleDictionary("Text") = "Sample text"），则可以编写 sampleDictionary.Text = "Sample text"。 此外，你希望此语法不区分大小写，因此 sampleDictionary.Text 等效于 sampleDictionary.text。

下面的代码示例演示 DynamicDictionary 了派生自该类的 DynamicObject 类。 DynamicDictionary 类包含用于存储键值对的 Dictionary<string, object> 类型 （Dictionary(Of String, Object) Visual Basic） 的对象，并重写 TrySetMember 和 TryGetMember 方法以支持新语法。 它还提供一个 Count 属性，该属性显示字典包含的动态属性数。

// The class derived from DynamicObject.
public class DynamicDictionary : DynamicObject
{
    // The inner dictionary.
    Dictionary<string, object> dictionary
        = new Dictionary<string, object>();

    // This property returns the number of elements
    // in the inner dictionary.
    public int Count
    {
        get
        {
            return dictionary.Count;
        }
    }

    // If you try to get a value of a property
    // not defined in the class, this method is called.
    public override bool TryGetMember(
        GetMemberBinder binder, out object result)
    {
        // Converting the property name to lowercase
        // so that property names become case-insensitive.
        string name = binder.Name.ToLower();

        // If the property name is found in a dictionary,
        // set the result parameter to the property value and return true.
        // Otherwise, return false.
        return dictionary.TryGetValue(name, out result);
    }

    // If you try to set a value of a property that is
    // not defined in the class, this method is called.
    public override bool TrySetMember(
        SetMemberBinder binder, object value)
    {
        // Converting the property name to lowercase
        // so that property names become case-insensitive.
        dictionary[binder.Name.ToLower()] = value;

        // You can always add a value to a dictionary,
        // so this method always returns true.
        return true;
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Creating a dynamic dictionary.
        dynamic person = new DynamicDictionary();

        // Adding new dynamic properties.
        // The TrySetMember method is called.
        person.FirstName = "Ellen";
        person.LastName = "Adams";

        // Getting values of the dynamic properties.
        // The TryGetMember method is called.
        // Note that property names are case-insensitive.
        Console.WriteLine(person.firstname + " " + person.lastname);

        // Getting the value of the Count property.
        // The TryGetMember is not called,
        // because the property is defined in the class.
        Console.WriteLine(
            "Number of dynamic properties:" + person.Count);

        // The following statement throws an exception at run time.
        // There is no "address" property,
        // so the TryGetMember method returns false and this causes a
        // RuntimeBinderException.
        // Console.WriteLine(person.address);
    }
}

// This example has the following output:
// Ellen Adams
// Number of dynamic properties: 2

' The class derived from DynamicObject.
Public Class DynamicDictionary
    Inherits DynamicObject

    ' The inner dictionary.
    Dim dictionary As New Dictionary(Of String, Object)

    ' This property returns the number of elements
    ' in the inner dictionary.
    ReadOnly Property Count As Integer
        Get
            Return dictionary.Count
        End Get
    End Property


    ' If you try to get a value of a property that is
    ' not defined in the class, this method is called.

    Public Overrides Function TryGetMember(
        ByVal binder As System.Dynamic.GetMemberBinder,
        ByRef result As Object) As Boolean

        ' Converting the property name to lowercase
        ' so that property names become case-insensitive.
        Dim name As String = binder.Name.ToLower()

        ' If the property name is found in a dictionary,
        ' set the result parameter to the property value and return true.
        ' Otherwise, return false.
        Return dictionary.TryGetValue(name, result)
    End Function

    Public Overrides Function TrySetMember(
        ByVal binder As System.Dynamic.SetMemberBinder,
        ByVal value As Object) As Boolean

        ' Converting the property name to lowercase
        ' so that property names become case-insensitive.
        dictionary(binder.Name.ToLower()) = value

        ' You can always add a value to a dictionary,
        ' so this method always returns true.
        Return True
    End Function
End Class

Sub Main()
    ' Creating a dynamic dictionary.
    Dim person As Object = New DynamicDictionary()

    ' Adding new dynamic properties.
    ' The TrySetMember method is called.
    person.FirstName = "Ellen"
    person.LastName = "Adams"

    ' Getting values of the dynamic properties.
    ' The TryGetMember method is called.
    ' Note that property names are now case-insensitive,
    ' although they are case-sensitive in C#.
    Console.WriteLine(person.firstname & " " & person.lastname)

    ' Getting the value of the Count property.
    ' The TryGetMember is not called, 
    ' because the property is defined in the class.
    Console.WriteLine("Number of dynamic properties:" & person.Count)

    ' The following statement throws an exception at run time.
    ' There is no "address" property,
    ' so the TryGetMember method returns false and this causes
    ' a MissingMemberException.
    ' Console.WriteLine(person.address)
End Sub
' This examples has the following output:
' Ellen Adams
' Number of dynamic properties: 2

有关更多示例，请参阅 C# 常见问题解答博客上的 DynamicObject 创建包装器 。

注解

通过 DynamicObject 该类，可以定义可以对动态对象执行的操作以及如何执行这些操作。 例如，可以定义尝试获取或设置对象属性、调用方法或执行标准数学运算（如加法和乘法）时会发生什么情况。

如果要为库创建更方便的协议，此类非常有用。 例如，如果库的用户必须使用类似 Scriptobj.SetProperty("Count", 1)语法，则可以提供使用更简单的语法的功能，例如 scriptobj.Count = 1。

不能直接创建类的 DynamicObject 实例。 若要实现动态行为，可能需要从 DynamicObject 类继承并重写必要的方法。 例如，如果只需要设置和获取属性的操作，可以只 TrySetMember 重写和 TryGetMember 方法。

在 C# 中，若要为派生自 DynamicObject 类的类实例启用动态行为，必须使用 dynamic 关键字。 有关详细信息，请参阅 “使用类型动态”。

在 Visual Basic 中，动态操作由后期绑定支持。 有关详细信息，请参阅早期绑定和后期绑定（Visual Basic）。

下面的代码示例演示如何创建派生自 DynamicObject 该类的类的实例。

public class SampleDynamicObject : DynamicObject {}
//...
dynamic sampleObject = new SampleDynamicObject ();

Public Class SampleDynamicObject
    Inherits DynamicObject
'...
Dim sampleObject As Object = New SampleDynamicObject()

还可以将自己的成员添加到派生自该类的 DynamicObject 类。 如果类定义属性并重写 TrySetMember 该方法，动态语言运行时 （DLR） 首先使用语言绑定器查找类中属性的静态定义。 如果没有此类属性，DLR 将调用该方法 TrySetMember 。

该 DynamicObject 类实现 DLR 接口 IDynamicMetaObjectProvider，使你可以在支持 DLR 互操作性模型的语言之间共享类的实例 DynamicObject 。 例如，可以在 C# 中创建类的 DynamicObject 实例，然后将其传递给 IronPython 函数。 有关详细信息，请参阅 动态语言运行时概述。