DefaultValueAttribute Class (System.ComponentModel)

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.NET Framework Class Library
DefaultValueAttribute Class

Specifies the default value for a property.

Inheritance Hierarchy

System.Object
  System.Attribute
    System.ComponentModel.DefaultValueAttribute

Namespace:  System.ComponentModel
Assembly:  System (in System.dll)
Syntax

Visual Basic
<AttributeUsageAttribute(AttributeTargets.All)> _
Public Class DefaultValueAttribute _
	Inherits Attribute
C#
[AttributeUsageAttribute(AttributeTargets.All)]
public class DefaultValueAttribute : Attribute
Visual C++
[AttributeUsageAttribute(AttributeTargets::All)]
public ref class DefaultValueAttribute : public Attribute
F#
[<AttributeUsageAttribute(AttributeTargets.All)>]
type DefaultValueAttribute =  
    class
        inherit Attribute
    end

The DefaultValueAttribute type exposes the following members.

Constructors

  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Boolean) Initializes a new instance of the DefaultValueAttribute class using a Boolean value.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Byte) Initializes a new instance of the DefaultValueAttribute class using an 8-bit unsigned integer.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Char) Initializes a new instance of the DefaultValueAttribute class using a Unicode character.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Double) Initializes a new instance of the DefaultValueAttribute class using a double-precision floating point number.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Int16) Initializes a new instance of the DefaultValueAttribute class using a 16-bit signed integer.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Int32) Initializes a new instance of the DefaultValueAttribute class using a 32-bit signed integer.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Int64) Initializes a new instance of the DefaultValueAttribute class using a 64-bit signed integer.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Object) Initializes a new instance of the DefaultValueAttribute class.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(Single) Initializes a new instance of the DefaultValueAttribute class using a single-precision floating point number.
Public method Supported by the XNA Framework Supported by Portable Class Library DefaultValueAttribute(String) Initializes a new instance of the DefaultValueAttribute class using a String.
Public method DefaultValueAttribute(Type, String) Initializes a new instance of the DefaultValueAttribute class, converting the specified value to the specified type, and using an invariant culture as the translation context.
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Properties

  Name Description
Public property TypeId When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)
Public property Supported by the XNA Framework Supported by Portable Class Library Value Gets the default value of the property this attribute is bound to.
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Methods

  Name Description
Public method Supported by the XNA Framework Supported by Portable Class Library Equals Returns whether the value of the given object is equal to the current DefaultValueAttribute. (Overrides Attribute.Equals(Object).)
Protected method Supported by the XNA Framework Supported by Portable Class Library Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method Supported by the XNA Framework Supported by Portable Class Library GetHashCode Returns the hash code for this instance. (Overrides Attribute.GetHashCode().)
Public method Supported by the XNA Framework Supported by Portable Class Library GetType Gets the Type of the current instance. (Inherited from Object.)
Public method 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.)
Public method Supported by the XNA Framework Match When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected method Supported by the XNA Framework Supported by Portable Class Library MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Protected method SetValue Sets the default value for the property to which this attribute is bound.
Public method Supported by the XNA Framework Supported by Portable Class Library ToString Returns a string that represents the current object. (Inherited from Object.)
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Explicit Interface Implementations

  Name Description
Explicit interface implemetation Private method _Attribute.GetIDsOfNames Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfo Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.GetTypeInfoCount Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetation Private method _Attribute.Invoke Provides access to properties and methods exposed by an object. (Inherited from Attribute.)
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Remarks

You can create a DefaultValueAttribute with any value. A member's default value is typically its initial value. A visual designer can use the default value to reset the member's value. Code generators can use the default values also to determine whether code should be generated for the member.

Note Note

A DefaultValueAttribute will not cause a member to be automatically initialized with the attribute's value. You must set the initial value in your code.

For more information, see Extending Metadata Using Attributes.

Examples

The following example sets the default value of MyProperty to false.

Visual Basic


    Private MyVar as Boolean = False
    <DefaultValue(False)> _
    Public Property MyProperty() As Boolean
        Get
            Return MyVar
        End Get
        Set
            MyVar = Value
        End Set 
    End Property



C#


private bool myVal=false;

[DefaultValue(false)]
 public bool MyProperty {
    get {
       return myVal;
    }
    set {
       myVal=value;
    }
 }


Visual C++

private:
   bool myVal;

public:
   [DefaultValue(false)]
   property bool MyProperty 
   {
      bool get()
      {
         return myVal;
      }

      void set( bool value )
      {
         myVal = value;
      }
   }


The next example checks the default value of MyProperty. First the code gets a PropertyDescriptorCollection with all the properties for the object. Next it indexes into the PropertyDescriptorCollection to get MyProperty. Then it returns the attributes for this property and saves them in the attributes variable.

The example then prints the default value by retrieving the DefaultValueAttribute from the AttributeCollection, and writing its name to the console screen.

Visual Basic

' Gets the attributes for the property.
Dim attributes As AttributeCollection = _
    TypeDescriptor.GetProperties(Me)("MyProperty").Attributes

' Prints the default value by retrieving the DefaultValueAttribute
' from the AttributeCollection. 
Dim myAttribute As DefaultValueAttribute = _
    CType(attributes(GetType(DefaultValueAttribute)), DefaultValueAttribute)
Console.WriteLine(("The default value is: " & myAttribute.Value.ToString()))


C#

// Gets the attributes for the property.
 AttributeCollection attributes = 
    TypeDescriptor.GetProperties(this)["MyProperty"].Attributes;

 /* Prints the default value by retrieving the DefaultValueAttribute 
  * from the AttributeCollection. */
 DefaultValueAttribute myAttribute = 
    (DefaultValueAttribute)attributes[typeof(DefaultValueAttribute)];
 Console.WriteLine("The default value is: " + myAttribute.Value.ToString());


Visual C++

// Gets the attributes for the property.
AttributeCollection^ attributes = TypeDescriptor::GetProperties( this )[ "MyProperty" ]->Attributes;

/* Prints the default value by retrieving the DefaultValueAttribute 
      * from the AttributeCollection. */
DefaultValueAttribute^ myAttribute = dynamic_cast<DefaultValueAttribute^>(attributes[ DefaultValueAttribute::typeid ]);
Console::WriteLine( "The default value is: {0}", myAttribute->Value );


Version Information

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library
Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
See Also

Reference