I have a wiki page and I want to retrieve an url of this page in an edit mode. The problem is that a url of this page in edit and display modes are the same. It doesn't change. How can I solve this problem? Thank you!
You need to pass the parameter ControlMode=Edit and DisplayMode=Design to the aspx page if you like to open it in edit mode.
@Stefan The page you mentioned is not a Wiki Page and its a Publishing Page(Placed in wiki Sub-site) and perhaps Publishing Pages is fine with this but for Wiki Pages that placed in SitePages Library use this query string:
When you create a new Wiki page via SharePoint 2013 UI, you will be redirected to the page with that query string.
For WebPart Pages use this query string: