Using Cascading DropDown

[C# Programming]

I'm using a cascading dropdownlist using three tables. the code below works fine if my primary keys are numeric(integer) but my business rules want the primary keys to be alphernumeric(string).



[WebMethod]
public CascadingDropDownNameValue[] GetColors(string knownCategoryValues, string category)
{
StringDictionary kv = CascadingDropDown.ParseKnownCategoryValuesString(knownCategoryValues);
int colorId;
if (!kv.ContainsKey("Model") || !Int32.TryParse(kv["Model"],out colorId))
{
return null;
}

dsModelColorsTableAdapters.ModelColorsTableAdapter adapter = new dsModelColorsTableAdapters.ModelColorsTableAdapter();
dsModelColors.ModelColorsDataTable colors = adapter.GetColorsByModelId(colorId);

List values = new List();
foreach (DataRow dr in colors)
{
values.Add(new CascadingDropDownNameValue((string)dr["ColorName"], dr["ColorID"].ToString()));
}
return values.ToArray();
}

How do I use my string primary key using the above code?
Please help an ajax technology adict.

ML Lingwati