In my application I work with criterias. I have one base Criteria interface and and other interfaces who inherits from this base interface:

               ICriteria
                  |
                  |
        ----------------------
         |                  |
    ITextCriteria        IChoices

What I'd like to know is, what is the best way to know what Type the class is?

In my code I have a dropdown box and based on that I have to determine the type:

// Get selected criteria
var selectedCriteria = cmbType.SelectedItem as ICriteria;

if (selectedCriteria is IChoices)
{
    //selectedCriteria = cmbType.SelectedItem as IChoices; Doesn't work
    IChoices criteria = selectedCriteria as IChoices;//cmbType.SelectedItem as IChoices;

    SaveMultipleChoiceValues(criteria);

    //_category.AddCriteria(criteria);
}
else
{
    //ICriteria criteria = selectedCriteria; //cmbType.SelectedItem as ICriteria;

    if (selectedCriteria.GetCriteriaType() == CriteriaTypes.None)
    {
        return;
    }

    //_category.AddCriteria(criteria);
}

_category.AddCriteria(selectedCriteria);

selectedCriteria.LabelText = txtLabeltext.Text;

this.Close();

My question is, is this the best way? Or is there a better way to achieve this?

The chance is big that there are coming more interfaces based on ICriteria.