How to check if object has been disposed in C

Question

Possible Duplicate    How does one tell if an IDisposable object reference is disposed        Is there a method to check if object has been disposed different then  try       myObj CallRandomMethod      catch  ObjectDisposedException e           now I know object has been disposed     In my case I m using TcpClient class that has Close   method which disposes object and this can happen in piece of code I don t have control of  In this case I would like to have better solution then catching exception

User · Answer

The reliable solution is catching the ObjectDisposedException.

The solution to write your overridden implementation of the Dispose method doesn't work, since there is a race condition between the thread calling Dispose method and the one accessing to the object: after having checked the hypothetic IsDisposed property , the object could be really disposed, throwing the exception all the same.

Another approach could be exposing a hypothetic event Disposed (like this), which is used to notify about the disposing object to every object interested, but this could be difficoult to plan depending on the software design.

User · Answer

If you re not sure whether the object has been disposed or not  you should call the Dispose method itself rather than methods such as Close  While the framework doesn t guarantee that the Dispose method must run without exceptions even if the object had previously been disposed  it s a common pattern and to my knowledge implemented on all disposable objects in the framework   The typical pattern for Dispose  as per Microsoft   public void Dispose          Dispose true           Use SupressFinalize in case a subclass        of this type implements a finalizer      GC SuppressFinalize this            protected virtual void Dispose bool disposing           If you need thread safety  use a lock around these         operations  as well as in your methods that use the resource      if    disposed                if  disposing                if   resource    null                   resource Dispose                    Console WriteLine  Object disposed                           Indicate that the instance has been disposed           resource   null           disposed   true               Notice the check on  disposed  If you were to call a Dispose method implementing this pattern  you could call Dispose as many times as you wanted without hitting exceptions

User · Answer

A good way is to derive from TcpClient and override the Disposing bool  method   class MyClient   TcpClient       public bool IsDead   get  set        protected override void Dispose bool disposing            IsDead   true          base Dispose disposing             Which won t work if the other code created the instance   Then you ll have to do something desperate like using Reflection to get the value of the private m CleanedUp member   Or catch the exception   Frankly  none is this is likely to come to a very good end   You really did want to write to the TCP port   But you won t  that buggy code you can t control is now in control of your code   You ve increased the impact of the bug   Talking to the owner of that code and working something out is by far the best solution   EDIT  A reflection example   using System Reflection  public static bool SocketIsDisposed Socket s       BindingFlags bfIsDisposed   BindingFlags Instance   BindingFlags NonPublic   BindingFlags GetProperty        Retrieve a FieldInfo instance corresponding to the field    PropertyInfo field   s GetType   GetProperty  CleanedUp   bfIsDisposed         Retrieve the value of the field  and cast as necessary    return  bool field GetValue s  null

User · Answer

Best practice says to implement it by your own using local boolean field  http   www niedermann dk 2009 06 18 BestPracticeDisposePatternC aspx

[c#] How to check if object has been disposed in C#

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