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SafeHandle.IsInvalid Property

When overridden in a derived class, gets a value indicating whether the handle value is invalid.

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

'Declaration
Public MustOverride ReadOnly Property IsInvalid As Boolean
'Usage
Dim instance As SafeHandle
Dim value As Boolean

value = instance.IsInvalid

/** @property */
public abstract boolean get_IsInvalid ()

public abstract function get IsInvalid () : boolean

Not applicable.

Property Value

true if the handle value is invalid; otherwise, false.

Derived classes must implement the IsInvalid property so that the common language runtime can determine whether critical finalization is required. Derived classes must provide an implementation that suits the general type of handle they support (0 or -1 is invalid). These classes can then be further derived for specific safe handle types.

Unlike the IsClosed property, which reports whether the SafeHandle object has finished using the underlying handle, the IsInvalid property calculates whether the given handle value is always considered invalid. Therefore, the IsInvalid property always returns the same value for any one handle value.

The following example checks if a file was opened successfully. This code example is part of a larger example provided for the SafeHandle class.

// Determine if file is opened successfully.
if (_handle.IsInvalid)
    throw new Win32Exception(Marshal.GetLastWin32Error(), fileName);

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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