Export (0) Print
Expand All
Expand Minimize
0 out of 1 rated this helpful - Rate this topic

Do not call overridable methods in constructors

TypeName

DoNotCallOverridableMethodsInConstructors

CheckId

CA2214

Category

Microsoft.Usage

Breaking Change

Non Breaking

The constructor of an unsealed type calls a virtual method defined in its class.

When a virtual method is called, the actual type that executes the method is not selected until run time. When a constructor calls a virtual method, it is possible that the constructor for the instance that invokes the method has not executed.

To fix a violation of this rule, do not call a type's virtual methods from within the type's constructors.

Do not suppress a warning from this rule. The constructor should be redesigned to eliminate the call to the virtual method.

The following example demonstrates the effect of violating this rule. The test application creates an instance of DerivedType, which causes its base class (BadlyConstructedType) constructor to execute. BadlyConstructedType's constructor incorrectly calls the virtual method DoSomething. As the output shows, DerivedType.DoSomething() executes, and does so before DerivedType's constructor executes.

using System;

namespace UsageLibrary
{
    public class BadlyConstructedType
    {
        protected   string initialized = "No";

        public BadlyConstructedType()
        {
            Console.WriteLine("Calling base ctor.");
            // Violates rule: DoNotCallOverridableMethodsInConstructors.
            DoSomething();
        }
        // This will be overridden in the derived type. 
        public virtual void DoSomething()
        {
            Console.WriteLine ("Base DoSomething");
        }
    }

    public class DerivedType : BadlyConstructedType
    {
        public DerivedType ()
        {
            Console.WriteLine("Calling derived ctor.");
            initialized = "Yes";
        }
        public override void DoSomething()
        {
            Console.WriteLine("Derived DoSomething is called - initialized ? {0}", initialized);
        }
    }

    public class TestBadlyConstructedType
    {
        public static void Main()
        {
            DerivedType derivedInstance = new DerivedType();
        }
    }
}

This example produces the following output.

Calling base ctor. Derived DoSomething is called - initialized ? No Calling derived ctor.
Did you find this helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

ADD
Show:
© 2014 Microsoft. All rights reserved.