How to invoke SubCategories in dropdown on the basis of Category selected in first dropdown

Hi,

Requirement is I have 2 dropdowns on my page.
First one displays Categories fetched from database
e.g. Category dropdowns displays data like this:
Id     Value
1      Cat1
2      Cat2

Cat1 have subcategories like SubCat11 & SubCat12
& Cat2 have subcategories like SubCat21 & SubCat22

My requirement is when I select Cat1, SubCategory dropdown should only display SubCat11 & SubCat12
& when I select Cat2, SubCategory dropdown should only fetch SubCat21 & SubCat22

I am new to NopCommerce & Dot Net.
I am able to display Categories from database on cshtml page, able to get changed CatId, send it to service & get Subcats for selected Category. But after trying for 4-5 hrs also not getting how to display this Subcat data in dropdown.
Kindly help. Thanks in advance.

read these and see if they help

https://www.nopcommerce.com/boards/t/11858/sub-cat-is-display-when-page-is-load.aspx

https://www.nopcommerce.com/boards/t/11949/how-to-generate-neat-multi-level-category-menu.aspx

Thanks for your reply. I went thru the links given but problem is not solved. Can you please explain a bit.

I have created 1 new method in Controller which takes 2 params. Depending upon param it will return Cat List or SubCat List.But not able to call this method from Action. Its giving error.
Please help. Thanks.

I don't know what you're expecting when / (or) if you even have more than 2 levels (cat / sub cat / sub-sub cat / etc.)...
But, I would think that if you're working with (or replacing) Views\Catalog\CategoryNavigation.cshtml, that you could just loop through the model IList<CategoryNavigationModel>, and based on category.NumberOfParentCategories, populate your dropdowns.