HI, I try to create Document type using console application. but it says

Value cannot be null.

public int CreateNewDocumentType(string title, string alias, string description)
        {
           
            User u = new User(0);
            DocumentType newDocument = DocumentType.MakeNew(u, "aasds");
           // newDocument.Alias = alias;
            newDocument.Description = description;
            newDocument.IconUrl = "doc.png";
            newDocument.Save();
                Document.RePublishAll();
            return DocumentType.GetByAlias(alias).Id;
         
            return 0;
        }

How can i solve that problem?

thanks.