FeatureSwitchDefinitionAttribute Class

Definition

Namespace:: System.Diagnostics.CodeAnalysis

Assembly:: System.Runtime.dll

Source:: FeatureSwitchDefinitionAttribute.cs

Important

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Indicates that the specified public static Boolean read-only property corresponds to the feature switch specified by name.

public ref class FeatureSwitchDefinitionAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Property, Inherited=false)]
public sealed class FeatureSwitchDefinitionAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Property, Inherited=false)>]
type FeatureSwitchDefinitionAttribute = class
    inherit Attribute

Public NotInheritable Class FeatureSwitchDefinitionAttribute
Inherits Attribute

Inheritance: Object

Attribute
FeatureSwitchDefinitionAttribute

Attributes: AttributeUsageAttribute

Examples

if (Feature.IsSupported)
    Feature.Implementation();

public class Feature
{
    [FeatureSwitchDefinition("Feature.IsSupported")]
    internal static bool IsSupported => AppContext.TryGetSwitch("Feature.IsSupported", out bool isEnabled) ? isEnabled : true;

    internal static Implementation() => ...;
}

When the app is trimmed with the following feature settings in the project file, Feature.IsSupported is treated as false, and Feature.Implementation code is removed.

<ItemGroup>
  <RuntimeHostConfigurationOption Include="Feature.IsSupported" Value="false" Trim="true" />
</ItemGroup>

Remarks

IL rewriters and compilers can use this attribute to substitute the return value of the specified property with the value of the feature switch.

The value of the feature switch can only be specified at the application level and affects the entire application. It is possible to get into situations where one library that is part of the application requires the feature switch to be turned on, but has no way to communicate this to the application author.

Feature switches complicate unit testing and code sharing since different application configurations might have different values of the feature switch, and it's difficult to ensure all code paths work as expected.

It is therefore preferable to structure APIs in a way that trimming can happen naturally without any feature switches. The use of feature switches should be reserved for situations where trimming needs to happen, but it's not feasible to change the APIs to allow trimming naturally.

Constructors

FeatureSwitchDefinitionAttribute(String)

Initializes a new instance of the FeatureSwitchDefinitionAttribute class

with the specified feature switch name.

Properties

SwitchName	The name of the feature switch that provides the value for the specified property.
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)

Applies to

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