Question

I ask myself how do I create a view model correctly.

For instance, I have an edit view with some text boxes and a dropdownlist.

Should I separate the dropdown list into a new view model or shoud the edit view have one viewmodel with a list for the dropdownlist?

Or generally speaking, should I separate special input fields in separate view models?

When should a view have more than one view model and when not?

Answer 1

There’s no clear rule of how to create and organize your view models correctly. Your question is too vague to be answered because you provided too little context.

I usually group view models according to functional blocks/parts of the screen they represent. So for example imagine that you have a complex form composed of multiple sections/fieldsets like contact details, delivery address, billing information, etc… An address could be composed of street, zip, city and country dropdown. I would create an address view model containing those four properties so that it can be reused in multiple views/partial views. This will also make validation easier as dependent properties will be packed into the same view model like validate for example that the given zip corresponds to the city and that the city belongs to the selected country.

For instance, I have an edit view with
some text boxes and a dropdownlist.

Should I separate the dropdown list
into a new view model or shoud the
edit view have one viewmodel with a
list for the dropdownlist?

I would say no, if those fields are somehow functionally related.

Conclusion: you will have to find the right balance between having a view model per field on the screen and having a single view model per application.