Implementing IDisposable correctly

Question

In my classes I implement IDisposable as follows  public class User   IDisposable       public int id   get  protected set        public string name   get  protected set        public string pass   get  protected set         public User int UserID                id   UserID            public User string Username  string Password                name   Username          pass   Password                Other functions go here         public void Dispose                    Clear all property values that maybe have been set            when the class was instantiated         id   0          name   String Empty          pass   String Empty           In VS2012  my Code Analysis says to implement IDisposable correctly  but I m not sure what I ve done wrong here  The exact text is as follows   CA1063 Implement IDisposable correctly Provide an overridable implementation of Dispose bool  on  User  or mark the type as sealed  A call to Dispose false  should only clean up native resources  A call to Dispose true  should clean up both managed and native resources  stman   User cs 10  For reference  CA1063  Implement IDisposable correctly I ve read through this page  but I m afraid I don t really understand what needs to be done here  If anyone can explain in more layman s terms what the problem is and or how IDisposable should be implemented  that will really help

User · Answer

This would be the correct implementation, although I don't see anything you need to dispose in the code you posted. You only need to implement IDisposable when:

You have unmanaged resources
You're holding on to references of things that are themselves disposable.

Nothing in the code you posted needs to be disposed.

public class User : IDisposable
{
    public int id { get; protected set; }
    public string name { get; protected set; }
    public string pass { get; protected set; }

    public User(int userID)
    {
        id = userID;
    }
    public User(string Username, string Password)
    {
        name = Username;
        pass = Password;
    }

    // Other functions go here...

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposing) 
        {
            // free managed resources
        }
        // free native resources if there are any.
    }
}

User · Answer

You have no need to do your User class being IDisposable since the class doesn t acquire any non-managed resources  file  database connection  etc    Usually  we mark classes as  IDisposable if they have at least one IDisposable field or and property     When implementing IDisposable  better put it according Microsoft typical scheme   public class User  IDisposable           protected virtual void Dispose Boolean disposing        if  disposing             There s no need to set zero empty values to fields           id   0           name   String Empty           pass   String Empty           TODO  free your true resources here  usually IDisposable fields               public void Dispose         Dispose true        GC SuppressFinalize this

User · Answer

IDisposable exists to provide a means for you to clean up unmanaged resources that won t be cleaned up automatically by the Garbage Collector   All of the resources that you are  cleaning up  are managed resources  and as such your Dispose method is accomplishing nothing   Your class shouldn t implement IDisposable at all   The Garbage Collector will take care of all of those fields just fine on its own

User · Answer

You need to use the Disposable Pattern like this   private bool  disposed   false   protected virtual void Dispose bool disposing        if    disposed                if  disposing                           Dispose any managed objects                                          Now disposed of any unmanaged objects                          disposed   true           public void Dispose         Dispose true       GC SuppressFinalize this           Destructor  YourClassName         Dispose false

User · Answer

I see a lot of examples of the Microsoft Dispose pattern which is really an anti-pattern   As many have pointed out the code in the question does not require IDisposable at all   But if you where going to implement it please don t use the Microsoft pattern   Better answer would be following the suggestions in this article   https   www codeproject com Articles 29534 IDisposable-What-Your-Mother-Never-Told-You-About  The only other thing that would likely be helpful is suppressing that code analysis warning     https   docs microsoft com en-us visualstudio code-quality in-source-suppression-overview view vs-2017

User · Answer

Idisposable is implement whenever you want a deterministic  confirmed  garbage collection   class Users   IDisposable                Users                         Dispose false                      public void Dispose                         Dispose true               GC SuppressFinalize this                  This method will remove current object from garbage collector s queue                 and stop calling finilize method twice                         public void Dispose bool disposer                        if  disposer                                   dispose the managed objects                              dispose the unmanaged objects                   When creating and using the Users class use  using  block to avoid explicitly calling dispose method    using  Users  user   new Users                                     do user related work                 end of the using block created Users object will be disposed by implicit invoke of dispose method

User · Answer

First of all  you don t need to  clean up  strings and ints - they will be taken care of automatically by the garbage collector   The only thing that needs to be cleaned up in Dispose are unmanaged resources or managed recources that implement IDisposable   However  assuming this is just a learning exercise  the recommended way to implement IDisposable is to add a  safety catch  to ensure that any resources aren t disposed of twice   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    disposed                if  disposing                            Clear all property values that maybe have been set                when the class was instantiated             id   0              name   String Empty              pass   String Empty                        Indicate that the instance has been disposed           disposed   true

User · Answer

The following example shows the general best practice to implement IDisposable interface  Reference   Keep in mind that you need a destructor finalizer  only if you have unmanaged resources in your class  And if you add a destructor you should suppress Finalization in the Dispose  otherwise it will cause your objects resides in memory for two garbage cycles  Note  Read how Finalization works   Below example elaborate all above   public class DisposeExample          A base class that implements IDisposable          By implementing IDisposable  you are announcing that         instances of this type allocate scarce resources       public class MyResource  IDisposable                  Pointer to an external unmanaged resource           private IntPtr handle             Other managed resource this class uses           private Component component   new Component               Track whether Dispose has been called           private bool disposed   false              The class constructor           public MyResource IntPtr handle                        this handle   handle                        Implement IDisposable              Do not make this method virtual              A derived class should not be able to override this method           public void Dispose                         Dispose true                  This object will be cleaned up by the Dispose method                  Therefore  you should call GC SupressFinalize to                 take this object off the finalization queue                 and prevent finalization code for this object                 from executing a second time              GC SuppressFinalize this                         Dispose bool disposing  executes in two distinct scenarios              If disposing equals true  the method has been called directly             or indirectly by a user s code  Managed and unmanaged resources             can be disposed              If disposing equals false  the method has been called by the             runtime from inside the finalizer and you should not reference             other objects  Only unmanaged resources can be disposed           protected virtual void Dispose bool disposing                           Check to see if Dispose has already been called               if  this disposed                                   If disposing equals true  dispose all managed                     and unmanaged resources                   if disposing                                           Dispose managed resources                      component Dispose                                          Call the appropriate methods to clean up                     unmanaged resources here                      If disposing is false                      only the following code is executed                  CloseHandle handle                   handle   IntPtr Zero                      Note disposing has been done                  disposed   true                                       Use interop to call the method necessary             to clean up the unmanaged resource           System Runtime InteropServices DllImport  Kernel32            private extern static Boolean CloseHandle IntPtr handle               Use C  destructor syntax for finalization code              This destructor will run only if the Dispose method             does not get called              It gives your base class the opportunity to finalize              Do not provide destructors in types derived from this class           MyResource                            Do not re-create Dispose clean-up code here                  Calling Dispose false  is optimal in terms of                 readability and maintainability              Dispose false                       public static void Main                    Insert code here to create             and use the MyResource object

[c#] Implementing IDisposable correctly

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