Attribute.IsDefaultAttribute Method

When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

public virtual bool IsDefaultAttribute()

Return Value

Type: System.Boolean
true if this instance is the default attribute for the class; otherwise, false.

The default implementation of this class returns false, and must be implemented in the derived class to be useful to that class.

The implementation of this method in a derived class compares the value of this instance to a standard default value, then returns a Boolean value that indicates whether the value of this instance is equal to the standard value. The standard value is typically coded as a constant in the implementation, or stored programmatically in a field used by the implementation.

The following code example illustrates the use of IsDefaultAttribute.

using System;
using System.Reflection;

namespace DefAttrCS 
{
    // An enumeration of animals. Start at 1 (0 = uninitialized). 
    public enum Animal 
    {
        // Pets.
        Dog = 1,
        Cat,
        Bird,
    }

    // A custom attribute to allow a target to have a pet. 
    public class AnimalTypeAttribute : Attribute 
    {
        // The constructor is called when the attribute is set. 
        public AnimalTypeAttribute(Animal pet) 
        {
            thePet = pet;
        }

        // Provide a default constructor and make Dog the default. 
        public AnimalTypeAttribute() 
        {
            thePet = Animal.Dog;
        }

        // Keep a variable internally ... 
        protected Animal thePet;

        // .. and show a copy to the outside world. 
        public Animal Pet 
        {
            get { return thePet; }
            set { thePet = Pet; }
        }

        // Override IsDefaultAttribute to return the correct response. 
        public override bool IsDefaultAttribute() 
        {
            if (thePet == Animal.Dog)
                return true;

            return false;
        }
    }

    public class TestClass 
    {
        // Use the default constructor.
        [AnimalType]
        public void Method1()
        {}
    }

    class DemoClass 
    {
        static void Main(string[] args) 
        {
            // Get the class type to access its metadata.
            Type clsType = typeof(TestClass);
            // Get type information for the method.
            MethodInfo mInfo = clsType.GetMethod("Method1");
            // Get the AnimalType attribute for the method.
            AnimalTypeAttribute atAttr = 
                (AnimalTypeAttribute)Attribute.GetCustomAttribute(mInfo,
                typeof(AnimalTypeAttribute));
            // Check to see if the default attribute is applied.
            Console.WriteLine("The attribute {0} for method {1} in class {2}",
                atAttr.Pet, mInfo.Name, clsType.Name); 
            Console.WriteLine("{0} the default for the AnimalType attribute.", 
                atAttr.IsDefaultAttribute() ? "is" : "is not");
        }
    }
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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