Namespace: System

AttributeUsageAttribute Class

Applies a user-defined attribute to an assembly, type, method, property, event, or parameter.

Namespace: System

Assembly: mscorlib (in mscorlib.dll)

Inheritance: Object
Attribute
AttributeUsageAttribute

Derived classes: None. Sealed.

Interfaces: None.

Syntax

[AttributeUsage(AttributeTargets.All, Inherited = true, AllowMultiple = false)]
public sealed class AttributeUsageAttribute : Attribute

Remarks

The AttributeUsageAttribute class is used to define custom attributes. When you create a custom attribute class, you can apply AttributeUsageAttribute to your attribute class to specify how the custom attribute can be used.

The AttributeUsageAttribute class has three properties:

AttributeUsageAttribute.AttributeUsageAttribute.AttributeTargets: Specifies the valid declaration in which the attribute can be applied.
AttributeUsageAttribute.Inherited: Specifies whether the attribute is inherited by derived classes and overrides.
AttributeUsageAttribute.AllowMultiple: Specifies whether the attribute can be applied more than once to the same declaration.

Constructors

AttributeUsageAttribute(AttributeTargets): Initializes a new instance of the AttributeUsageAttribute class with specified attribute usage information.

Properties

AllowMultiple (inherited from Attribute): Gets a value that indicates whether one or more instances of the attribute can be applied to the same assembly, type, or member.
AttributeTargets: Gets the declaration that is permitted to be decorated with the attribute.
Inherited (inherited from Attribute): Gets a value that indicates whether the attribute is inherited by derived classes and overrides.

Methods

GetHashCode() (inherited from Object): Returns the hash code for this instance.
GetType() (inherited from Object): Gets the Type of the current instance.
IsDefaultAttribute() (inherited from Attribute): Determines whether the specified attribute is the default attribute for this attribute type.
Match(Object) (inherited from Attribute): When overridden in a derived class, determines whether the specified attribute matches the current attribute.
ToString() (inherited from Object): Returns a string that represents the current object.

Example

The following example demonstrates how to create a custom attribute named CodeDescriptionAttribute and apply the AttributeUsageAttribute to it. This custom attribute can be applied to any code element, is not inherited, and can be applied multiple times.

using System;

[AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)]
public class CodeDescriptionAttribute : Attribute
{
    private string description;

    public CodeDescriptionAttribute(string description)
    {
        this.description = description;
    }

    public string Description
    {
        get { return description; }
    }
}

public class ExampleClass
{
    [CodeDescription("This is a sample method.")]
    [CodeDescription("Another description for the same method.")]
    public void SampleMethod()
    {
        // Method implementation
    }
}

Explanation:

AttributeTargets.All: The attribute can be applied to any declaration (class, method, property, etc.).
Inherited = false: The attribute is not inherited by derived classes.
AllowMultiple = true: The attribute can be applied more than once to the same declaration.

Microsoft Docs