How to bind Dictionary with ComboBox and textbox?

I have a Dictionary<String,Person>, where Person is a class, defined below

String role;

public class Person
{ 
  public string firstname{ get; set; } 
  public string lastname{ get; set; } 

  public string city{ get; set; } 
} 

My question is how to bind the Dictionary key: String with a ComboBox, meanwhile. have the Dictionary value: Person connected with thr开发者_运维问答ee textboxes. That is, once a key is selected in the ComboBox, the corresponding value, firstname, lastname, city are shown in the three textboxes respectively?

Thanks in advance!

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Note: Not copy-pastable code... exists solely to get the point across.

View

I see some controls with the databinding as shown below in the Window/View...

<Combobox ItemsSource="{Binding Path=AlphabeticalIds}" Text="{Binding Path=SelectedId}"/>
<TextBox Text="{Binding Path=SelectedPerson.FirstName}"/>
<TextBox Text="{Binding Path=SelectedPerson.LastName}"/>
<TextBox Text="{Binding Path=SelectedPerson.City}"/>

ViewModel

An instance of this class is set as the datacontext of the view. It has the following members. (They're exposed as .NET Properties ; NotifyPropertyChange calls identify the properties that require change notification)

_mapIdToPerson = Dict...

_alphabeticalIds = _map...Keys.Sort();

_selectedId;
set 
{
  _selectedId = value;
  _selectedPerson = _mapIdToPerson[_selectedId];
  NotifyPropertyChange("SelectedId");
  NotifyPropertyChange("SelectedPerson");
}

_selectedPerson;