Edit Lookup Values with RadComboBox

RadDataForm gives you the opportunity to edit the current item's properties directly as well as displaying and using lookup ones. This is easily achievable by using a RadComboBox and defining its required properties.

For the purpose of this tutorial we will create two quite simple classes - Person and Country:

Example 1: Creating the Person and Country Classes

C#

	public class Person
	{
	    public string FirstName { get; set; }
	    public string LastName { get; set; }
	    public int CountryID { get; set; }
	}
	public class Country
	{
	    public int ID { get; set; }
	    public string Name { get; set; }
	}

VB.NET

	Public Class Person
	    Public Property FirstName() As String
	        Get
	            Return m_FirstName
	        End Get
	        Set(value As String)
	            m_FirstName = value
	        End Set
	    End Property
	    Private m_FirstName As String
	    Public Property LastName() As String
	        Get
	            Return m_LastName
	        End Get
	        Set(value As String)
	            m_LastName = value
	        End Set
	    End Property
	    Private m_LastName As String
	    Public Property CountryID() As Integer
	        Get
	            Return m_CountryID
	        End Get
	        Set(value As Integer)
	            m_CountryID = value
	        End Set
	    End Property
	    Private m_CountryID As Integer
	End Class
	Public Class Country
	    Public Property ID() As Integer
	        Get
	            Return m_ID
	        End Get
	        Set(value As Integer)
	            m_ID = value
	        End Set
	    End Property
	    Private m_ID As Integer
	    Public Property Name() As String
	        Get
	            Return m_Name
	        End Get
	        Set(value As String)
	            m_Name = value
	        End Set
	    End Property
	    Private m_Name As String
	End Class

Afterwards, we may add the source of the RadDataForm:

Example 2: Set the ItemsSource

C#

	InitializeComponent();
	List<Person> persons = new List<Person>();
	// A sample list of source objects for the RadDataForm. 
	persons.Add(new Person() { FirstName = "John", LastName = "Smith", CountryID = 1 });
	persons.Add(new Person() { FirstName = "Angelo", LastName = "Romano", CountryID = 2 });
	persons.Add(new Person() { FirstName = "Jean", LastName = "Michel", CountryID = 3 });
	this.RadDataForm1.ItemsSource = persons;

VB.NET

	InitializeComponent()
	Dim persons As New List(Of Person)()
	' A sample list of source objects for the RadDataForm. 
	persons.Add(New Person() With {
	 .FirstName = "John",
	 .LastName = "Smith",
	 .CountryID = 1
	})
	persons.Add(New Person() With {
	 .FirstName = "Angelo",
	 .LastName = "Romano",
	 .CountryID = 2
	})
	persons.Add(New Person() With {
	 .FirstName = "Jean",
	 .LastName = "Michel",
	 .CountryID = 3
	})
	Me.RadDataForm1.ItemsSource = persons

Now, in order to edit the lookup values we have to do two things:

• Create a source for the RadComboBox - we'll create a CountriesService class with a public static GetCountries() method

Example 3: Creating a CountriesService Class with a Static GetCountries() Method

C#

	public class CountriesService
	{
	    public static List<Country> GetCountries()
	    {
	        List<Country> countries = new List<Country>();
	        countries.Add(new Country() { ID = 1, Name = "USA" });
	        countries.Add(new Country() { ID = 2, Name = "Italy" });
	        countries.Add(new Country() { ID = 3, Name = "France" });
	        countries.Add(new Country() { ID = 4, Name = "Canada" });
	        return countries;
	    }
	}

VB.NET

	Public Class CountriesService
	    Public Shared Function GetCountries() As List(Of Country)
	        Dim countries As New List(Of Country)()
	        countries.Add(New Country() With {
	                .ID = 1,
	                .Name = "USA"
	            })
	        countries.Add(New Country() With {
	                .ID = 2,
	                .Name = "Italy"
	            })
	        countries.Add(New Country() With {
	                .ID = 3,
	                .Name = "France"
	            })
	        countries.Add(New Country() With {
	                .ID = 4,
	                .Name = "Canada"
	            })
	        Return countries
	    End Function
	End Class

• Define the RadComboBox as a field in the RadDataForm. To achieve this we have two options - to handle the AutoGeneratingField event and define a DataFormComboBoxField or create a template for the ReadOnlyTemplate, EditTemplate and NewItemTemplate:

1. Scenario 1 - handle the AutoGeneratingField:

Example 4: Handling the AutoGeneratingField Event

C#

	private void RadDataForm_AutoGeneratingField(object sender, Telerik.Windows.Controls.Data.DataForm.AutoGeneratingFieldEventArgs e)
	{
	    if (e.PropertyName == "CountryID")
	    {
	        e.DataField = new DataFormComboBoxField()
	        {
	            ItemsSource = CountriesService.GetCountries(),
	            SelectedValuePath = "ID",
	            DisplayMemberPath = "Name",
	            DataMemberBinding = new Binding("CountryID") { Mode = BindingMode.TwoWay }
	        };
	    }
	}

VB.NET

	Private Sub RadDataForm_AutoGeneratingField(sender As Object, e As Telerik.Windows.Controls.Data.DataForm.AutoGeneratingFieldEventArgs)
	    If e.PropertyName = "CountryID" Then
	        e.DataField = New DataFormComboBoxField() With {
	         .ItemsSource = CountriesService.GetCountries(),
	         .SelectedValuePath = "ID",
	         .DisplayMemberPath = "Name",
	         .DataMemberBinding = New Binding("CountryID") With {
	         .Mode = BindingMode.TwoWay
	         }
	        }
	    End If
	End Sub

Figure 1 shows the resulting RadDataForm:

Figure 1: The DataFormComboBoxField

2. Scenario 2 - define the template for the ReadOnlyTemplate, EditTemplate and NewItemTemplate:

Example 5: Defining the Template for ReadOnlyTemplate, EditTemplate and NewItemTemplate

XAML

	<UserControl.Resources>
	    <my:MyViewModel x:Key="MyViewModel" />
	</UserControl.Resources>
	<Grid x:Name="LayoutRoot" Background="White" DataContext="{StaticResource MyViewModel}">
	    <Grid.Resources>
	        <DataTemplate x:Key="MyTemplate">
	            <Grid>
	                <Grid.ColumnDefinitions>
	                    <ColumnDefinition/>
	                    <ColumnDefinition/>
	                </Grid.ColumnDefinitions>
	                <Grid.RowDefinitions>
	                    <RowDefinition/>
	                    <RowDefinition/>
	                </Grid.RowDefinitions>
	                <telerik:DataFormDataField Label="First Name" DataMemberBinding="{Binding FirstName, Mode=TwoWay}" Grid.Row="0" Grid.Column="0"/>
	                <telerik:DataFormDataField Label="Last Name" DataMemberBinding="{Binding LastName, Mode=TwoWay}" Grid.Row="0" Grid.Column="1"/>
	                <telerik:DataFormComboBoxField SelectedValuePath="ID" DisplayMemberPath="Name"
	                      Grid.Row="2" Grid.Column="1" DataMemberBinding="{Binding CountryID, Mode=TwoWay}"
	                      ItemsSource="{Binding Countries, Source={StaticResource MyViewModel}}" />
	            </Grid>
	        </DataTemplate>
	    </Grid.Resources>
	    <telerik:RadDataForm x:Name="RadDataForm1"
	        AutoGenerateFields="False"
	        Header="Person"
	        ItemsSource="{Binding Persons}"
	        ReadOnlyTemplate="{StaticResource MyTemplate}"
	        EditTemplate="{StaticResource MyTemplate}"
	        NewItemTemplate="{StaticResource MyTemplate}">
	    </telerik:RadDataForm>
	</Grid>

In this case the Countries and Persons collections used for the ItemsSources of the ComboBoxField and the RadDataForm are defined in the ViewModel class:

Example 6: Defining the Countries and Persons Collections in the ViewModel

C#

	public class MyViewModel
	{
	    private List<Country> countries;
	    private List<Person> persons;
	    public List<Country> Countries
	    {
	        get
	        {
	            if (this.countries == null)
	            {
	                this.countries = CountriesService.GetCountries();
	            }
	            return this.countries;
	        }
	    }
	    public List<Person> Persons
	    {
	        get
	        {
	            if (this.persons == null)
	            {
	                List<Person> persons = new List<Person>();
	                persons.Add(new Person() { FirstName = "John", LastName = "Smith", CountryID = 1 });
	                persons.Add(new Person() { FirstName = "Angelo", LastName = "Romano", CountryID = 2 });
	                persons.Add(new Person() { FirstName = "Jean", LastName = "Michel", CountryID = 3 });
	                this.persons = persons;
	            }
	            return this.persons;
	        }
	    }
	}

VB.NET

	Public Class MyViewModel
	    Private m_countries As List(Of Country)
	    Private m_persons As List(Of Person)
	    Public ReadOnly Property Countries() As List(Of Country)
	        Get
	            If Me.m_countries Is Nothing Then
	                Me.m_countries = CountriesService.GetCountries()
	            End If
	            Return Me.m_countries
	        End Get
	    End Property
	    Public ReadOnly Property Persons() As List(Of Person)
	        Get
	            If Me.m_persons Is Nothing Then
	                Dim persons__1 As New List(Of Person)()
	                persons__1.Add(New Person() With {
	                    .FirstName = "John",
	                    .LastName = "Smith",
	                    .CountryID = 1
	                })
	                persons__1.Add(New Person() With {
	                    .FirstName = "Angelo",
	                    .LastName = "Romano",
	                    .CountryID = 2
	                })
	                persons__1.Add(New Person() With {
	                    .FirstName = "Jean",
	                    .LastName = "Michel",
	                    .CountryID = 3
	                })
	                Me.m_persons = persons__1
	            End If
	            Return Me.m_persons
	        End Get
	    End Property
	End Class

The result will be same as the one in the first scenario.