AngularJS ng-options with several fields

I have a collection of objects with user info.

"Id": "1",
"Firstname": "ABCDEF",
"Lastname": "GHIJK",
"Middlename": ""

In my select options I want to display two fields - Firstname Lastname. I don't get how to do it and how to bind it to ng-model.

You can try this :

<select 
  name="users" 
  ng-model="selectedUser" 
  ng-options="user.Id as user.Firstname + ' ' + user.Lastname for user in users">
</select>

More information here : http://docs.angularjs.org/api/ng.directive:select

Considering the format of your array object to be like this.

$scope.userInfo = [
                    {"Id": "1", "Firstname": "ACDEF", "Lastname": "GHIJK", "Middlename": ""},
                    {"Id": "2", "Firstname": "BADEF", "Lastname": "HIGJK", "Middlename": ""},
                    {"Id": "3", "Firstname": "CDBEF", "Lastname": "IIHJK", "Middlename": ""},
                ]

You can display two fields like this and and bind it to the model as shown below.

<select ng-model="userInfo" ng-options="s.Firstname +' '+ s.Lastname for s in userInfo" class="span2"> </select>