How to loop rows of dataset in Reporting services rdl custom code

Question

How can I loop through the rows of a dataset in the custom code?
I have a report containing a dataset. I pass the dataset as a parameter to the custom code function. But what then? Where is a reference about the available members etc.?
Here is my dummy sample code so far:

Public Function ShowParameterValues(ByVal ds as DataSet) as object()
    Dim codes() As Object
    Array.Resize(codes,dc.???.Count)
    codes(0)=ds??(field???)(row??)
    return codes
End Function

Please note: this will be a very simple script (if it'll work), so I don't want to go into custom assemblies etc.