C# abstract classes and methods in aggregation situations - how?

The implementation of the class must have the same parameters:

public class AggregateClass : BaseAggregateClass
{
    private ComponentClass m_attribute;
    private bool m_valid;

    public override bool Valid
    {
        get
        {
            return m_valid;
        }
    }

    public override bool Check()
    {
        checkVal(m_attribute);
        return m_valid;
    }

    public override void checkVal(BaseComponentClass attrib)
    {
        if (attrib.Value == null)
            m_valid = false;
    }
}

You will then get a warning as you a testing an int for null which will always be false.