.NET Memory Profiler API Examples

The .NET Memory Profiler API allows you to automatically detect memory leaks and control the profiler from within the profiled process.

Potential memory leaks are detected by applying assertions to the code that should be tested. There are three ways of applying the assertions:

Using the old-style memory assertions. Click here for an example.
Using the AssertionsDefinition class. Click here for an example.
Using attributes to declaratively define the expected memory usage of a method. Click here for an example.

If the memory assertion fails, a dialog will be shown by the profiler. This dialog will present information about the failed assertion and allow you to decide on actions to perform.

Click the image to magnify.

Memory Assertion Examples

Below are three examples of how memory assertions can be performed. All three examples perform the same memory assertion, with different approaches. Even though the AssertionsDefinition approach is a bit more verbose, it is recommended over the old-style assertions, since it provides much more flexibility and more assertions, like MaxNewInstances, MaxInstances, and MaxNewBytes.

Detect Memory Leaks using the old-style Assertions

The code below shows how memory assertions can be used to detect whether new instances have unintentionally been created by an action. The action in this case is to show a dialog, and that action should not result in any new System.ComponentModel.Component instances.

        void ShowSomeDialog()

        {

          // Establish a base snapshot

          MemProfiler.FastSnapShot();

          using( SomeDialog dlg = new SomeDialog() )

          {

            dlg.ShowDialog();

          }

          // Assert that no new Component instances have been

          // created. The FastSnapshot collected at the
        
          // beginning of the method will be used as
        
          // reference.

          MemAssertion.NoNewInstances( typeof(Component), true );

        }

Detect Memory Leaks using `AssertionsDefinition`

The code below shows how the AssertionsDefinition class can be used to detect whether new instances have unintentionally been created by an action. The action in this case is to show a dialog, and that action should not result in any new System.ComponentModel.Component instances.

        void ShowSomeDialog()

        {

          // Establish a base snapshot

          MemProfiler.FastSnapShot();

          using( SomeDialog dlg = new SomeDialog() )

          {

            dlg.ShowDialog();

          }

          // Assert that no new Component instances have been

          // created. The FastSnapshot collected at the
        
          // beginning of the method will be used as
        
          // reference.

          using( MemAssertion.BeginAssertions() )

          {

            AssertionsDefinition ad = new AssertionsDefinition();

            ad.NoNewInstances( typeof( Component ), true );

            MemAssertion.Assert( ad );

          }

        }

Detect Memory Leaks using Attributes

The code below shows how an assertion attribute can be used to detect whether new instances have unintentionally been created by a method. In this example we have method that shows a dialog and closes it. After this method has been executed, no new instances of System.ComponentModel.Component should exist. This is declared by applying the NoNewInstances attribute to the method.

        [NoNewInstances(typeof( Component ), IncludeSubclasses = true )]

        void ShowSomeDialog()

        {

          using( SomeDialog dlg = new SomeDialog() )

          {

            dlg.ShowDialog();

          }

        }

Unit Testing

It is also possible to use the API together with a unit testing framework, like NUnit. All memory assertion methods return a boolean value, indicating whether the assertion was successful. This value can be used as argument to a unit testing assertion:

        [Test]

        void TestShowDialog()

        {

           MemProfiler.FastSnapshot();

           ShowDialog();

           Assert.IsTrue( MemAssertion.NoNewInstances(...) );

        }

By using command line arguments to the profiler, the profiler can run without any user interaction, allowing completely automated testing of memory leaks.