Generics in Blazor component

I am writing a component that requries a generic parameter to be declared. I do not have my code in the page within a code block, but instead use a partial class.

All the examples I've found show that in the page it takes the form:

@typeparam TItem;@code {    [Parameter]    public TItem ExampleList { get; set; }....

how can I declare this using a class file? If I declare typeparam in the page and place my parameter declaration in the partial class, 'TItem' is not recognised. and I do not seem to be able to declare typeparam in the code behind.