S3909 — Collections should implement the generic interface

Why is this an issue?

The NET Framework 2.0 introduced the generic interface System.Collections.Generic.IEnumerable<T> and it should be preferred over the older, non generic, interfaces.

This rule raises an issue when a public type implements System.Collections.IEnumerable.

Noncompliant code example

using System;
using System.Collections;

public class MyData
{
  public MyData()
  {
  }
}

public class MyList : CollectionBase // Noncompliant
{
  public void Add(MyData data)
  {
    InnerList.Add(data);
  }

  // ...
}

Compliant solution

using System;
using System.Collections.ObjectModel;

public class MyData
{
  public MyData()
  {
  }
}

public class MyList : Collection<MyData>
{
  // Implementation...
}