Code inspection: Cast expression can be replaced with explicit variable type

C-style cast expression in C# can be both a static upcast and a dynamic downcast, both having the same syntax. Without keeping the type hierarchies in mind, there is no way to tell if the cast is a safe upcast or a runtime downcast. Moreover, a static upcast can be accidentally turned into a dynamic downcast during a refactoring. To avoid these problems and make code less fragile, this inspection suggests using an explicit type instead of the cast where possible.

            
interface IBase;
interface IDerived : IBase;
class Derived : IDerived;

class Sample
{
    public Sample()
    {
        var derivedInstance = new Derived();

// upcast:
        var baseReference = (IBase) derivedInstance;

// downcast:
        var derivedReference = (IDerived) baseReference;
    }
}

        

            
interface IBase;
interface IDerived : IBase;
class Derived : IDerived;

class Sample
{
    public Sample()
    {
        var derivedInstance = new Derived();

// implicit upcast:
        IBase baseReference = derivedInstance;

// downcast:
        var derivedReference = (IDerived) baseReference;
    }
}

        

Such initialization of baseReference will not compile if the derivedInstance variable changes its type so that it is no longer compatible with IBase.

Last modified: 25 July 2024