== Why is this an issue?

Needing to cast from an ``++interface++`` to a concrete type indicates that something is wrong with the abstractions in use, likely that something is missing from the ``++interface++``. Instead of casting to a discrete type, the missing functionality should be added to the ``++interface++``. Otherwise there is a risk of runtime exceptions.


=== Noncompliant code example

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

public class MyClass1 : IMyInterface
{
  public int Data { get { return new Random().Next(); } }

  public void DoStuff()
  {
    // TODO...
  }
}

public static class DowncastExampleProgram
{
  static void EntryPoint(IMyInterface interfaceRef)
  {
    MyClass1 class1 = (MyClass1)interfaceRef;  // Noncompliant
    int privateData = class1.Data;

    class1 = interfaceRef as MyClass1;  // Noncompliant
    if (class1 != null)
    {
      // ...
    }
  }
}
----


=== Exceptions

Casting to ``++object++`` doesn't raise an issue, because it can never fail.

[source,csharp]
----
static void EntryPoint(IMyInterface interfaceRef)
{
  var o = (object)interfaceRef;
  ...
}
----


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== Implementation Specification
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== Comments And Links
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include::../comments-and-links.adoc[]

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