How to make a generic list equal another generic list
<p>This is my set up,</p>

<pre><code>class CostPeriodDto : IPeriodCalculation
{
    public decimal? a { get; set; }
    public decimal? b { get; set; }
    public decimal? c { get; set; }
    public decimal? d { get; set; }
}

interface IPeriodCalculation
{
    decimal? a { get; set; }
    decimal? b { get; set; }
}

class myDto
{
    public List&lt;CostPeriodDto&gt; costPeriodList{ get; set; }

    public List&lt;IPeriodCalculation&gt; periodCalcList
    {
        get
        {
            return this.costPeriodList;  // compile error   
        }
    }
}
</code></pre>

<p>What would be the best way of doing this?</p>
