asp.net - How do you remove invalid characters when creating a friendly url (ie how do you create a slug)? -

I have this webpage:

if the category Id = 1 is named "dogs" "I would like to convert the URL to something like this:

The problem is that the class name contains the foreign (or invalid for the URL) characters if the category Id = 2 is named" blond alldre " What should be the new URL, then?

Logically it should be:
äldre
But this will not work first because of space (which I I can change mash by example, for example) but what about foreign characters? I can use the URLEncode function in Asp.net which would have to give something like this:

But I really want to do this Can not say that it is better than the original url ()

Ideally I would like to generate this one but how can I do it automatically (i.e. foreign characters have 'safe' url characters To convert):