DefaultParameterValueAttribute DefaultParameterValueAttribute DefaultParameterValueAttribute DefaultParameterValueAttribute Class

定义

设置当从支持默认参数的语言中调用参数时参数的默认值。Sets the default value of a parameter when called from a language that supports default parameters. 此类不能被继承。This class cannot be inherited.

public ref class DefaultParameterValueAttribute sealed : Attribute
[System.AttributeUsage(System.AttributeTargets.Parameter)]
public sealed class DefaultParameterValueAttribute : Attribute
type DefaultParameterValueAttribute = class
    inherit Attribute
Public NotInheritable Class DefaultParameterValueAttribute
Inherits Attribute
继承
DefaultParameterValueAttributeDefaultParameterValueAttributeDefaultParameterValueAttributeDefaultParameterValueAttribute
属性

示例

下面的代码示例演示如何将DefaultParameterValueAttribute特性应用于在中C#编写的方法的参数。The following code example demonstrates how to apply the DefaultParameterValueAttribute attribute to a parameter of a method written in C#.

static public void MethodWithDefaultParam([System.Runtime.InteropServices.DefaultParameterValue("DEFAULT_PARAM_VALUE")] string var)
{
	Console.WriteLine("The passed value is: " + var);
}

注解

使用DefaultParameterValueAttribute特性, 可以在不支持默认参数的语言中指定默认参数值。The DefaultParameterValueAttribute attribute allows you to specify a default parameter value in a language that does not otherwise support default parameters. 将此特性应用于代码后, 支持默认参数的语言可以使用指定的值作为默认参数。After you apply this attribute to your code, languages that support default parameters can use the specified value as a default parameter.

请注意, DefaultParameterValueAttribute不会向不支持此功能的语言添加对默认参数的支持。Note that the DefaultParameterValueAttribute does not add support for default parameters to languages that do not support this feature. 例如, 如果你将DefaultParameterValueAttribute与编写的方法C#(不支持默认参数) 一起使用, 则在从C#调用该方法时, 不能使用默认参数。For example, if you use the DefaultParameterValueAttribute with a method written in C#, which does not support default parameters, you cannot use the default parameter when calling the method from C#. 仅当使用支持功能的语言 (如) C++调用方法时, 才可以使用默认参数。You can use the default parameter only when calling the method in a language such as C++ that does support the feature.

DefaultParameterValueAttribute对于指定 COM 互操作接口的方法的默认参数, 特别有用。The DefaultParameterValueAttribute is particularly useful to specify default parameters for methods of a COM interop interface.

构造函数

DefaultParameterValueAttribute(Object) DefaultParameterValueAttribute(Object) DefaultParameterValueAttribute(Object) DefaultParameterValueAttribute(Object)

用参数的默认值初始化 DefaultParameterValueAttribute 类的新实例。Initializes a new instance of the DefaultParameterValueAttribute class with the default value of a parameter.

属性

TypeId TypeId TypeId TypeId

在派生类中实现时,获取此 Attribute 的唯一标识符。When implemented in a derived class, gets a unique identifier for this Attribute.

(Inherited from Attribute)
Value Value Value Value

获取参数的默认值。Gets the default value of a parameter.

方法

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

返回一个值,该值指示此实例是否与指定的对象相等。Returns a value that indicates whether this instance is equal to a specified object.

(Inherited from Attribute)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

返回此实例的哈希代码。Returns the hash code for this instance.

(Inherited from Attribute)
GetType() GetType() GetType() GetType()

获取当前实例的 TypeGets the Type of the current instance.

(Inherited from Object)
IsDefaultAttribute() IsDefaultAttribute() IsDefaultAttribute() IsDefaultAttribute()

在派生类中重写时,指示此实例的值是否是派生类的默认值。When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.

(Inherited from Attribute)
Match(Object) Match(Object) Match(Object) Match(Object)

当在派生类中重写时,返回一个指示此实例是否等于指定对象的值。When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.

(Inherited from Attribute)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

返回表示当前对象的字符串。Returns a string that represents the current object.

(Inherited from Object)

显式界面实现

_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr) _Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr) _Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr) _Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

将一组名称映射为对应的一组调度标识符。Maps a set of names to a corresponding set of dispatch identifiers.

(Inherited from Attribute)
_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr) _Attribute.GetTypeInfo(UInt32, UInt32, IntPtr) _Attribute.GetTypeInfo(UInt32, UInt32, IntPtr) _Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

检索对象的类型信息,然后可以使用该信息获取接口的类型信息。Retrieves the type information for an object, which can be used to get the type information for an interface.

(Inherited from Attribute)
_Attribute.GetTypeInfoCount(UInt32) _Attribute.GetTypeInfoCount(UInt32) _Attribute.GetTypeInfoCount(UInt32) _Attribute.GetTypeInfoCount(UInt32)

检索对象提供的类型信息接口的数量(0 或 1)。Retrieves the number of type information interfaces that an object provides (either 0 or 1).

(Inherited from Attribute)
_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr) _Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr) _Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr) _Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

提供对某一对象公开的属性和方法的访问。Provides access to properties and methods exposed by an object.

(Inherited from Attribute)

适用于