Question

Suppose we have a factory for returning partials containing the logic to select a certain one. I would like some to delegate that responsibility to a factory and then write a neat code inside the controller:

    [HttpGet]
    public PartialViewResult GetQueryItemForCategory(string categoryName, bool campaignSelected)
    {
        return QueryItemBuilderFactory.BuildPartial(categoryName, campaignSelected);
    } 

But I really cannot call the PartialView() method inside that factory.

public static class QueryItemBuilderFactory
{
    private static Dictionary<string, Func<bool, PartialViewResult>> _builderActions =
        new Dictionary<string, Func<bool, PartialViewResult>>();
    static QueryItemBuilderFactory()
    {
        _builderActions.Add("Data Field", campaignSelected =>
                                            {
                                                return  PartialView("_DataFieldQueryItemPartial");
                                            });
    }

    public static PartialViewResult BuildPartial(string categoryName, bool campaignSelected)
    {
        return _builderActions[categoryName](campaignSelected);
    }
}

Is there any way to implement it?

Answer 1

The protected PartialView methods is defined on the base Controller class:

public abstract class Controller : ControllerBase, IActionFilter,
    IAuthorizationFilter, IDisposable, IExceptionFilter, IResultFilter
{
    ...

    protected internal PartialViewResult PartialView()
    {
        ...
    }

    protected internal PartialViewResult PartialView(object model)
    {
        ...
    }

    protected internal PartialViewResult PartialView(string viewName)
    {
        ...
    }

    ...
}

So inheriting from this Controller class enables you to use this method, whereas it’s not available in other situations.
However, as you can see the PartialView methods return PartialViewResult objects so replacing

return PartialView("_DataFieldQueryItemPartial");

in your example with

return new PartialViewResult(){ ViewName = "_DataFieldQueryItemPartial" };

will do the trick.