After a long time going through lots of different forum entries and tutorials, I finally managed to piece together a little bit of Razor code to generate a multilangue dropdown. I am using a multi site structure and wanted to link relations if available in the corresponding language. The culture settings from ASP weren't formatted the way I wanted and hence I decided to create a property on my top level language folder (just below the content folder). In that property I add the language names my preferred spelling.

If a page is not yet translated in a certain language, then I still want all available languages to be diplayed. If a page cannot be accessed via a relation then the top level page should be displayed for the chosen language.

Here is my razor script:

@using umbraco.MacroEngines;
@using umbraco.cms.businesslogic.relation;
@using umbraco.cms.businesslogic.member;
@inherits umbraco.MacroEngines.DynamicNodeContext

@{
  var TopLanguageNode = Model.AncestorOrSelf(1);
    DynamicNode contentRoot = new DynamicNode(-1);
    RelationType relationType = RelationType.GetByAlias("relateDocumentOnCopy");
    Relation[] relations = Relation.GetRelations(Model.Id, relationType);
}  

<select name="langselection" onchange="window.open(this.options[this.selectedIndex].value,'_top')">
 @foreach (DynamicNode LanguageRoots in contentRoot.Descendants("Lang Top Folder Alias"))
  {
     var curLanguage = LanguageRoots.GetProperty("Language Property Alias").Value.ToString();
      var curUrl = LanguageRoots.Url;
       
      foreach(Relation relation in relations)
       {
         int relationId = relation.Parent.Id;
          if(relationId == Model.Id)
            {
             relationId = relation.Child.Id;
           }
         var TopLangPage = Model.NodeById(relationId).AncestorOrSelf(1);
           
          if(curLanguage == TopLangPage.Language)
           {
             curUrl = Model.NodeById(relationId).Url;
          }
     }   
      
      if(curLanguage == TopLanguageNode.Language)
       {
         <option value="@curUrl" selected="selected">@curLanguage</option>
     }
     else
      {
         <option value="@curUrl">@curLanguage</option>
     }
 }
</select>

Any feedback would be much appreciated. I used Vizioz relations to make the page relations visible in the backend.

When copying the language folders a missing feature in my opinion is that all existing relations should be analysed when copying a language folder structure. e.g. if page a is related to page b then page b is copied to create page c, then c and a should also be related, if the relation checkbox was selected.