DefaultParameterValueAttribute 類別

定義

設定從支援預設參數的語言呼叫參數時,該參數的預設值。Sets the default value of a parameter when called from a language that supports default parameters. 此類別無法被繼承。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
繼承
DefaultParameterValueAttribute
屬性

範例

下列程式碼範例示範如何將 DefaultParameterValueAttribute 屬性套用至以撰寫之方法的參數C#。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);
}

備註

DefaultParameterValueAttribute 屬性可讓您以不支援預設參數的語言指定預設參數值。The DefaultParameterValueAttribute attribute allows you to specify a default parameter value in a language that does not otherwise support default parameters. 將此屬性套用至您的程式碼之後,支援預設參數的語言可以使用指定的值做為預設參數。After you apply this attribute to your code, languages that support default parameters can use the specified value as a default parameter.

請注意,DefaultParameterValueAttribute 不會將預設參數的支援新增至不支援這項功能的語言。Note that the DefaultParameterValueAttribute does not add support for default parameters to languages that do not support this feature. 例如,如果您將 DefaultParameterValueAttribute 與以C#撰寫的方法(不支援預設參數)搭配使用,則從C#呼叫方法時,不能使用預設參數。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#. 只有在以支援功能的語言C++呼叫方法時,才可以使用預設參數。You can use the default parameter only when calling the method in a language such as C++ that does support the feature.

DefaultParameterValueAttribute 特別適合用來指定 COM Interop 介面之方法的預設參數。The DefaultParameterValueAttribute is particularly useful to specify default parameters for methods of a COM interop interface.

建構函式

DefaultParameterValueAttribute(Object)

使用參數的預設值,初始化 DefaultParameterValueAttribute 類別的新執行個體。Initializes a new instance of the DefaultParameterValueAttribute class with the default value of a parameter.

屬性

TypeId

在衍生類別中實作時,取得這個 Attribute 的唯一識別碼。When implemented in a derived class, gets a unique identifier for this Attribute.

(繼承來源 Attribute)
Value

取得參數的預設值。Gets the default value of a parameter.

方法

Equals(Object)

傳回值,這個值指出此執行個體是否與指定的物件相等。Returns a value that indicates whether this instance is equal to a specified object.

(繼承來源 Attribute)
GetHashCode()

傳回這個執行個體的雜湊碼。Returns the hash code for this instance.

(繼承來源 Attribute)
GetType()

取得目前執行個體的 TypeGets the Type of the current instance.

(繼承來源 Object)
IsDefaultAttribute()

在衍生類別中覆寫時,表示這個執行個體的值是衍生類別的預設值。When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.

(繼承來源 Attribute)
Match(Object)

在衍生類別中覆寫時,會傳回值,表示這個執行個體是否等於指定物件。When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.

(繼承來源 Attribute)
MemberwiseClone()

建立目前 Object 的淺層複製。Creates a shallow copy of the current Object.

(繼承來源 Object)
ToString()

傳回代表目前物件的字串。Returns a string that represents the current object.

(繼承來源 Object)

明確介面實作

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

將一組名稱對應至一組對應的分派識別項 (Dispatch Identifier)。Maps a set of names to a corresponding set of dispatch identifiers.

(繼承來源 Attribute)
_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

擷取物件的類型資訊,可以用來取得介面的類型資訊。Retrieves the type information for an object, which can be used to get the type information for an interface.

(繼承來源 Attribute)
_Attribute.GetTypeInfoCount(UInt32)

擷取物件提供的類型資訊介面數目 (0 或 1)。Retrieves the number of type information interfaces that an object provides (either 0 or 1).

(繼承來源 Attribute)
_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

提供物件所公開的屬性和方法的存取權。Provides access to properties and methods exposed by an object.

(繼承來源 Attribute)

適用於