V3072. The 'A' class containing IDisposable members does not itself implement IDisposable.

The analyzer detected that a class, which does not implement 'IDisposable' interface, contains fields or properties of a type that does implement 'IDisposable'. Such code indicates that a programmer probably forgot to release resources after using an object of their class.

Consider the following example:

class Logger
{
  FileStream fs;
  public Logger() {
    fs = File.OpenWrite("....");
  }
}

In this code, the wrapper class, which allows writing the log to a file, does not implement 'IDisposable' interface. At the same time, it contains a variable of type 'FileStream', which enables writing to a file. In this case, the 'fs' variable will be holding the file until the Finalize method of the 'fs' object is called (it will happen when the object is being cleared by the garbage collector). As a result, we get an access error, behaving like a heisenbug and occurring, for example, when attempting to open the same file from a different stream.

This issue can be fixed in a number of ways. The most correct one is as follows:

class Logger : IDisposable
{
  FileStream fs;
  public Logger() {
    fs = File.OpenWrite("....");
  }
  public void Dispose() { 
    fs.Dispose();
  }
}

However, the program logic does not always allow you implement 'IDisposable' in the 'Logger' class. The analyzer checks many scenarios and reduces the number of false positives. In our code above, for example, we can simply close 'FileStream', which writes to a file, from a separate function:

class Logger
{
  FileStream fs;
  public Logger() {
    fs = File.OpenWrite("....");
  }
  public void Close() { 
    fs.Close();
  }
}