Silverlight bind collection to Combobox in DataForm using MVVM
I have this problem, I've got Silverlight app written using MVVM. I need to create DataForm which is binded to property on ViewModel and I want to add ComboBox and fill it with values from other collection in the same ViewModel.
Code:
<dataFormToolkit:DataForm CurrentItem="{Binding NewUser, Mode=TwoWay}" AutoGenerateFields="False" Height="298">
<dataFormToolkit:DataForm.EditTemplate>
<DataTemplate>
<StackPanel>
<dataFormToolkit:DataField Label="Email">
<TextBox Text="{Binding Email, Mode=TwoWay}"/>
</dataFormToolkit:DataField>
<dataFormToolkit:DataField Label="Język">
<ComboBox ItemsSource="{Binding Path=Languages, Mode=TwoWay}"/>
</dataFormToolkit:DataField>
</StackPanel>
</DataTemplate>
</dataFormToolkit:DataForm.EditTemplate>
</dataFormToolkit:DataForm>
All this is handled by NewAccountVM which has these properties:
private User newUser;
public User NewUser {
get
{
return newUser;
}
set
{
if (value != newUser)
{
newUser = value;
RaisePropertyChanged("NewUser");
}
}
}
private ObservableCollection<Language> languages;
public ObservableCollection<Language> Languages
{
get { return languages; }
set
{
if (languages != value)
{
languages = value;
RaisePropertyChanged("Languages");
}
}
}
Now, all this works besides adding ItemsSource to ComboBox. I've found many examples showing how fill CB in CodeBehind, but like I said I want to do this in MVVM-Style :) I understand that, ComboBox inherited DataContext from DataForm, and this ItemsSource="{Binding Path=Languages, Mode=TwoWay}" will not work, but I have no idea how to achieve my goal.
Can somebody help me?
1) Declare the viewmodel to the view in the resources section.
<UserControl.Resources>
<local:MyViewModel x:Key="myViewModel" />
</UserControl.Resources>
2) Bind the ComboBox to the collection property on the viewmodel.
<ComboBox ItemsSource="{Binding Path=Languages,
Source={StaticResource myViewModel},
Mode=TwoWay}"/>
您可以将XAML中的数据上下文设置为静态资源，如下所示：
<UserControl.DataContext>
<Binding Source="{StaticResource myViewModel}" />
</UserControl.DataContext>
Scenario A: 1. Assume you wish to populate a combo with all the membership Roles, and allow the client to select the role and assign to the User : ie ObjectA : Aspnet_Role ie ObjectB : User
Let us say User.MembershipRoleId is to be bound to Aspnet_Role.RoleId
Dataform is bound to ObjectB
In XAML write the following:
<Combobox DisplayMemberPath="RoleName" SelectedValue="{Binding MembershipRoleId,Mode=TwoWay}" SelectedValuePath="RoleId" />
here the mapping is, ObjectB.MembershipRoleId=ObjectA.RoleId
Scenario B: 1. If you do not want to explicitly define by the way in ScenarioA, then in that case, define a ForeignKey-PrimaryKey relationship between the tables in the database like ForeignKey -> User.MembershipId PrimaryKey -> Aspnet_Roles.RoleId 2. From the ADO.NET (.edmx) file, update the model from the database, you will observe that in the User entity there is an association made upon entity Aspnet_Roles 3. In XAML write the code as below to bind the combobox, to the desired field of the Dataform
<Combobox DisplayMemberPath="RoleName" SelectedItem="{Binding MembershipRoleId,Mode=TwoWay}" .... />