New SPField shows in the view of my SPList but doesn't appear in any forms (edit, new)

Question

I add a new column to a SharePoint list (the list is built on a content type) like this:

        SPField textfield = list.Fields.CreateNewField(SPFieldType.Text.ToString(), "new column");
        list.Fields.Add(textfield);            
        list.Update();

        //the new field must be editable!
        SPField newField = list.Fields["new column"];
        newField.ShowInEditForm = true;
        newField.ShowInViewForms = true;
        newField.ShowInDisplayForm = true;
        newField.ShowInNewForm = true;
        newField.Update();

        //update the view
        SPView view = list.DefaultView;
        view.ViewFields.Add(language);
        view.Update(); 

The new column appears in the default view of the list and everything appears to work just fine. However, when I try to add a new item or edit an existing item, my new column doesn't appear in the form. A quick look in PowerShell reveals that "CanBeShowInEditForm" is set to true. What am I missing here?

Answer 1

Your missing adding the field as fieldlink to the Lists version for the content type

var ct = list.ContentTypes["NameOfCT"];
var fieldLink = new SPFieldLink(newField);
ct.FieldLinks.Add(fieldLink);
ct.Update()

When you're using content types in a list only the fields corresponding to the content type is shown in forms. But all fields can be shown in views.