rspec/rules/S4039/csharp/rule.adoc

When a base type explicitly implements a public interface method, that method is only accessible in derived types through a reference to the current instance (namely ``++this++``). If the derived type explicitly overrides that interface method, the base implementation becomes inaccessible.


This rule raises an issue when an unsealed, externally visible type provides an explicit method implementation of a ``++public interface++`` and does not provide an alternate, externally visible method with the same name.


== Noncompliant Code Example

[source,csharp]
----
public interface IMyInterface
{
    void MyMethod();
}

public class Foo : IMyInterface
{
    void IMyInterface.MyMethod() // Noncompliant
    {
        MyMethod();
    }

    void MyMethod()
    {
        // Do something ...
    }
}

public class Bar : Foo, IMyInterface
{
    public void MyMethod()
    {
        // Can't access base.MyMethod()
        // ((IMyInterface)this).MyMethod() would be a recursive call
    }
}
----


== Compliant Solution

[source,csharp]
----
public interface IMyInterface
{
    void MyMethod();
}

public class Foo : IMyInterface
{
    void IMyInterface.MyMethod()
    {
        MyMethod();
    }

    protected void MyMethod() // or public
    {
        // Do something ...
    }
}

public class Bar : Foo, IMyInterface
{
    public void MyMethod()
    {
        // Do something
        base.MyMethod();
    }
}
----


== Exceptions

This rule does not report a violation for an explicit implementation of ``++IDisposable.Dispose++`` when an externally visible ``++Close()++`` or ``++System.IDisposable.Dispose(Boolean)++`` method is provided.

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== Implementation Specification
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