ReturnValueNameAttribute Class

Definition

Namespace:

System.Runtime.InteropServices.WindowsRuntime

Assembly:

System.Runtime.InteropServices.WindowsRuntime.dll

Specifies the name of the return value of a method in a Windows Runtime component.

public ref class ReturnValueNameAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Delegate | System.AttributeTargets.ReturnValue, AllowMultiple=false, Inherited=false)]
public sealed class ReturnValueNameAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Delegate | System.AttributeTargets.ReturnValue, AllowMultiple=false, Inherited=false)>]
type ReturnValueNameAttribute = class
    inherit Attribute

Public NotInheritable Class ReturnValueNameAttribute
Inherits Attribute

Inheritance

Object

Attribute

ReturnValueNameAttribute

Attributes

AttributeUsageAttribute

Remarks

In a Windows Runtime component, all the parameters of a method and the return value must have names. By default, Winmdexp.exe (Windows Runtime Metadata Export Tool) gives the return value the name "value". When you use a component in a Windows 8.x Store app written in JavaScript, you can use this name to retrieve the return value. For example, suppose a component defines a method that has a return value and two out parameters (ByRef parameters with the OutAttribute attribute in Visual Basic):

public static int ComputeAverage([ReadOnlyArray()] int[] input,  
    out int minValue, out int maxValue)  
{  
    …  
}  

Public Shared Function ComputeAverage( _  
        <ReadOnlyArray()> ByVal input As Integer, _  
        <Out()> ByRef minValue As Integer, _  
        <Out()> ByRef maxValue As Integer) As Integer  
    …  
End Function  

When you call the function from JavaScript, you can access the return value by its default name (value):

var data = [5, 13, 23, 37];  
var results = SampleComponent.TestStuff.computeAverage(data);  
var formattedResults = "Min=" + results.minValue + ", Avg=" +   
    results.value + ", Max=" + results.maxValue;  

You must give the return value a different name if you already have a parameter named "value". Or you might simply want to use a more meaningful name (such as "average" in this example). Apply the ReturnValueNameAttribute attribute to your method and specify a new name.

[return: ReturnValueName("average")]  
public static int ComputeAverage([ReadOnlyArray()] int[] input,  
    out int minValue, out int maxValue)  
{  
    …  
}  

Public Shared Function ComputeAverage( _  
        <ReadOnlyArray()> ByVal input As Integer, _  
        <Out()> ByRef minValue As Integer, _  
        <Out()> ByRef maxValue As Integer) _  
            As <ReturnValueName("average")> Integer  
    …  
End Function  

Constructors

ReturnValueNameAttribute(String)

Initializes a new instance of the ReturnValueNameAttribute class, and specifies the name of the return value.

Properties

Name	Gets the name that was specified for the return value of a method in a Windows Runtime component.
TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute)

Methods

Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute)
GetHashCode()	Returns the hash code for this instance. (Inherited from Attribute)
GetType()	Gets the Type of the current instance. (Inherited from Object)
IsDefaultAttribute()	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)	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

See also

• Creating Windows Runtime Components in C# and Visual Basic