Artikel
11/17/2011

NullReferenceException Class

Microsoft Silverlight will reach end of support after October 2021. Learn more.

The exception that is thrown when there is an attempt to dereference a null object reference.

Inheritance Hierarchy

System.Object
  System.Exception
    System.SystemException
      System.NullReferenceException

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

Syntax

'Declaration
<ComVisibleAttribute(True)> _
Public Class NullReferenceException _
    Inherits SystemException

[ComVisibleAttribute(true)]
public class NullReferenceException : SystemException

The NullReferenceException type exposes the following members.

Constructors

	Name	Description
	NullReferenceException()	Initializes a new instance of the NullReferenceException class, setting the Message property of the new instance to a system-supplied message that describes the error, such as "The value 'null' was found where an instance of an object was required." This message takes into account the current system culture.
	NullReferenceException(String)	Initializes a new instance of the NullReferenceException class with a specified error message.
	NullReferenceException(String, Exception)	Initializes a new instance of the NullReferenceException class with a specified error message and a reference to the inner exception that is the cause of this exception.

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Properties

	Name	Description
	Data	Gets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception.)
	HResult	Gets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception.)
	InnerException	Gets the Exception instance that caused the current exception. (Inherited from Exception.)
	Message	Gets a message that describes the current exception. (Inherited from Exception.)
	StackTrace	Gets a string representation of the frames on the call stack at the time the current exception was thrown. (Inherited from Exception.)

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Methods

	Name	Description
	Equals(Object)	Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	GetBaseException	When overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception.)
	GetHashCode	Serves as a hash function for a particular type. (Inherited from Object.)
	GetType	Gets the runtime type of the current instance. (Inherited from Exception.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Creates and returns a string representation of the current exception. (Inherited from Exception.)

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Remarks

Note that applications throw the ArgumentNullException exception rather than the NullReferenceException exception discussed here.

The following Microsoft intermediate language (MSIL) instructions throw NullReferenceException :

callvirt
cpblk
cpobj
initblk
ldelem.<type>
ldelema
ldfld
ldflda
ldind.<type>
ldlen
stelem.<type>
stfld
stind.<type>
throw
unbox

NullReferenceException uses the HRESULT COR_E_NULLREFERENCE, which has the value 0x80004003.

For a list of initial property values for an instance of NullReferenceException, see the NullReferenceException constructors.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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.

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