CA1001: Types that own disposable fields should be disposable

Cause

A class declares and implements an instance field that is a System.IDisposable type and the class does not implement IDisposable.

Rule Description

A class implements the IDisposable interface to dispose of unmanaged resources that it owns. An instance field that is an IDisposable type indicates that the field owns an unmanaged resource. A class that declares an IDisposable field indirectly owns an unmanaged resource and should implement the IDisposable interface. If the class does not directly own any unmanaged resources, it should not implement a finalizer.

How to Fix Violations

To fix a violation of this rule, implement IDisposable and from the IDisposable.Dispose method call the Dispose method of the field.

When to Suppress Warnings

Do not suppress a warning from this rule.

Example

The following example shows a class that violates the rule and a class that satisfies the rule by implementing IDisposable. The class does not implement a finalizer because the class does not directly own any unmanaged resources.

Imports System
Imports System.IO

Namespace DesignLibrary

   ' This class violates the rule. 
   Public Class NoDisposeMethod

      Dim newFile As FileStream

      Sub New()
         newFile = New FileStream("c:\temp.txt", FileMode.Open)
      End Sub 

   End Class 

   ' This class satisfies the rule. 
   Public Class HasDisposeMethod 
      Implements IDisposable

      Dim newFile As FileStream

      Sub New()
         newFile = New FileStream("c:\temp.txt", FileMode.Open)
      End Sub 

      Overloads Protected Overridable Sub Dispose(disposing As Boolean)

         If disposing Then 
            ' dispose managed resources
            newFile.Close()
         End If 

         ' free native resources 

      End Sub 'Dispose


      Overloads Public Sub Dispose() Implements IDisposable.Dispose

         Dispose(True)
         GC.SuppressFinalize(Me)

      End Sub 'Dispose

   End Class 

End Namespace

using System;
using System.IO;

namespace DesignLibrary
{
   // This class violates the rule. 
   public class NoDisposeMethod
   {
      FileStream newFile;

      public NoDisposeMethod()
      {
         newFile = new FileStream(@"c:\temp.txt", FileMode.Open);
      }
   }

   // This class satisfies the rule. 
   public class HasDisposeMethod: IDisposable
   {
      FileStream newFile;

      public HasDisposeMethod()
      {
         newFile = new FileStream(@"c:\temp.txt", FileMode.Open);
      }

      protected virtual void Dispose(bool disposing)
      {
         if (disposing)
            {
               // dispose managed resources
               newFile.Close();
            }
          // free native resources
      }

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

Related Rules

CA2213: Disposable fields should be disposed

CA2216: Disposable types should declare finalizer

CA2215: Dispose methods should call base class dispose

CA1049: Types that own native resources should be disposable