V3068. Calling overrideable class member from constructor is dangerous.


The analyzer detected a potential error inside a class constructor - invoking an overridable method (virtual or abstract). The following example shows how such call can lead to an error:

abstract class Base
{
    protected Base()
    {
        Initialize();
    }

    protected virtual void Initialize()
    {
    ...
    }
}

class Derived : Base
{
    Logger _logger;
    public Derived(Logger logger)
    {
        _logger = logger;
    }

    protected override void Initialize()
    {
        _logger.Log("Initializing");
        base.Initialize();
    }
}

In this code, the constructor of abstract class Base contains a call to virtual method Initialize. In the Derived class, which is derived from the Base class, we override the Initialize method and utilize the _logger field in this overridden method. The _logger field itself is initialized in the Derived class's constructor.

However, when creating an instance of the Derived class, the constructor of the less derived type in the inheritance sequence will be executed first (Base class in our case). But when calling to the Initialize method from Base's constructor, we'll be executing the Initialize method of the object created at runtime, i.e. the Derived class. Note that when executing the Initialize method, the _logger field will not be initialized yet, so creating an instance of the Derived class in our example will cause a NullReferenceException.

Therefore, invoking overridable methods in a constructor may result in executing methods of an object whose initialization is not complete yet.

To fix the analyzer warning, either mark the method you are calling (or the class that contains it) as sealed or remove the virtual keyword from its definition.

If you do want the program to behave as described above when initializing an object and you want to hide the analyzer's warning, mark the message as a false positive. For details about warning-suppression methods, see the documentation.


Bugs Found

Checked Projects
334
Collected Errors
12 668