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Core.DefaultValueAttribute Class (F#)

Den Delimarsky|Last Updated: 8/18/2017
1 Contributor

Adding this attribute to a field declaration means that the field is not initialized. During type checking a constraint is asserted that the field type supports null. If the Check value is false then the constraint is not asserted.

Namespace/Module Path: Microsoft.FSharp.Core

Assembly: FSharp.Core (in FSharp.Core.dll)


[<AttributeUsage(AttributeTargets.Field, AllowMultiple = false)>]
type DefaultValueAttribute =
new DefaultValueAttribute : bool -> DefaultValueAttribute
new DefaultValueAttribute : unit -> DefaultValueAttribute
member this.Check :  bool


This attribute is intended to be used on explicit fields in classes and structures. It shouldn't be used on records. For more information, see Records (F#) and Explicit Fields: The val Keyword (F#).

The .NET Framework namespace System.ComponentModel defines an attribute that has the same name: System.ComponentModel.DefaultValueAttribute. Therefore, you must fully qualify the F# attribute if you open the System.ComponentModel namespace.

You can also use the short form of the name, DefaultValue.


newCreates an instance of the attribute

Instance Members

CheckIndicates if a constraint is asserted that the field type supports 'null'


Windows 8, Windows 7, Windows Server 2012, Windows Server 2008 R2

Version Information

F# Core Library Versions

Supported in: 2.0, 4.0, Portable

See Also

Microsoft.FSharp.Core Namespace (F#)

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