andrepaulo andrepaulo - 4 years ago 147
Vb.net Question

MVVM WPF datagrid Selected binding to combobox with complex object

I'm trying to implement a DataGrid wich one of the columns has a complex object and the comboBox (out of the grid) has a list of the same time object of this column. Using WPF and MVVM.

When I select the Line in the datagrid, I want the combo box to Show the corresponding value.

But I don't know what am I doing wrong.
Can anyone help?

<ComboBox x:Name="cmbResourceList"
HorizontalAlignment="Left"
ItemsSource="{Binding MainListSource}"
DisplayMemberPath="Description"
SelectedValue="{Binding Path=ScheduleVM.Schedule.ResourceList}"
Width="185"/>

<DataGrid x:Name="dgScheduleItems"
AutoGenerateColumns="False"
ItemsSource="{Binding Path=ScheduleSource}"
SelectionMode="Single"
IsReadOnly="True"
SelectedItem="SelectedSchedule">

<DataGrid.Columns>
<DataGridTextColumn Header="Id" Binding="{Binding Id}" Width="40"/>
<DataGridTextColumn Header="Resource List" Binding="{Binding ResourceList.Description}" Width="*"/>
<DataGridTextColumn Header="Task List" Binding="{Binding TaskList.Description}" Width="*"/>
<DataGridTextColumn Header="Description" Binding="{Binding Description}" Width="100"/>
</DataGrid.Columns>

</DataGrid>


And here The classes in Vb.Net

Public Class MainList
Public Property Id As Integer
Public Property Description As String
End Class


Public Class Schedule
Public Property Id As Integer
Public Property Description As String
Public Property ResourceList As MainList
Public Property TaskList As MainList
End Class


Public Class MainListRepository
Private _mainLists As List(Of MainList)

Public Sub New()
_mainLists = New List(Of MainList) From
{
New MainList() With {.Id = 1, .Description = "First List"},
New MainList() With {.Id = 2, .Description = "Second List"},
New MainList() With {.Id = 3, .Description = "Third List"}
}
End Sub

Public Function GetMainLists() As List(Of MainList)
Return _mainLists
End Function
End Class


Public Class ScheduleRepository
Private _schedules As List(Of Schedule)

Public Sub New()
_schedules = New List(Of Schedule) From
{
New Schedule() With {.Id = 1, .Description = "Schedule 1", .ResourceList = New MainList() With {.Id = 2, .Description = "Second List"}, .TaskList = New MainList() With {.Id = 1, .Description = "First List"}},
New Schedule() With {.Id = 2, .Description = "Schedule 2", .ResourceList = New MainList() With {.Id = 1, .Description = "First List"}, .TaskList = New MainList() With {.Id = 2, .Description = "Second List"}},
New Schedule() With {.Id = 3, .Description = "Schedule 3", .ResourceList = New MainList() With {.Id = 1, .Description = "First List"}, .TaskList = New MainList() With {.Id = 3, .Description = "Third List"}},
New Schedule() With {.Id = 4, .Description = "Schedule 4", .ResourceList = New MainList() With {.Id = 3, .Description = "Third List"}, .TaskList = New MainList() With {.Id = 1, .Description = "First List"}}
}
End Sub

Public Function GetSchedules() As List(Of Schedule)
Return _schedules
End Function
End Class

Public MustInherit Class ViewModelBase
Implements INotifyPropertyChanged

Protected Sub New()
End Sub

Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

Protected Overridable Sub OnPropertyChanged(ByVal propertyName As String)
Me.VerifyPropertyName(propertyName)

Dim handler As PropertyChangedEventHandler = Me.PropertyChangedEvent
If handler IsNot Nothing Then
Dim e = New PropertyChangedEventArgs(propertyName)
handler(Me, e)
End If
End Sub

Private privateThrowOnInvalidPropertyName As Boolean
Protected Overridable Property ThrowOnInvalidPropertyName() As Boolean
Get
Return privateThrowOnInvalidPropertyName
End Get
Set(ByVal value As Boolean)
privateThrowOnInvalidPropertyName = value
End Set
End Property
End Class

Public Class ScheduleVM
Inherits ViewModelBase

Private _Schedule As Schedule
Public Property Schedule() As Schedule
Get
Return _Schedule
End Get
Set(ByVal value As Schedule)
_Schedule = value

OnPropertyChanged("Schedule")
End Set
End Property

Public Sub New(schedule As Schedule)
_Schedule = schedule
End Sub

End Class


Friend Class SchedulePopupVM
Inherits ViewModelBase

Private _ScheduleSource As List(Of Schedule)
Public Property ScheduleSource() As List(Of Schedule)
Get
Return _ScheduleSource
End Get
Set(ByVal value As List(Of Schedule))
_ScheduleSource = value

OnPropertyChanged("ScheduleSource")
End Set
End Property

Private _MainListSource As List(Of MainList)
Public Property MainListSource() As List(Of MainList)
Get
Return _MainListSource
End Get
Set(ByVal value As List(Of MainList))
_MainListSource = value

OnPropertyChanged("MainListSource")
End Set
End Property


Private _SelectedSchedule As Schedule
Public Property SelectedSchedule() As Schedule
Get
Return _SelectedSchedule
End Get
Set(ByVal value As Schedule)
_SelectedSchedule = value
Me.ScheduleVM = New ScheduleVM(value)

OnPropertyChanged("SelectedSchedule")
End Set
End Property

Private _ScheduleVM As ScheduleVM
Public Property ScheduleVM() As ScheduleVM
Get
Return _ScheduleVM
End Get
Set(ByVal value As ScheduleVM)
_ScheduleVM = value

OnPropertyChanged("ScheduleVM")
End Set
End Property

Public Sub New()
Dim repo As ScheduleRepository = New ScheduleRepository()
Dim repoMain As MainListRepository = New MainListRepository()

_ScheduleSource = repo.GetSchedules()
_MainListSource = repoMain.GetMainLists()

End Sub

End Class

Answer Source

A few things.

Both of your SelectedValues (on your ComboBox) are bound to item collections. You do not want this, these properties are meant to be bound to individual items within the item collection.

Next, your binding for the SelectedItem of your DataGrid is wrong. Update it to (notice binding keyword and braces):

  <DataGrid x:Name="dgScheduleItems"   
      AutoGenerateColumns="False" 
      ItemsSource="{Binding Path=ScheduleSource}" 
      SelectionMode="Single"
      IsReadOnly="True"
      SelectedItem="{Binding SelectedSchedule}"
      Margin="0,106,0,0">

Next, for your ComboBoxes, you then want to bind to an individual value. Though, the value you are binding to for SelectedValue must be a reference to one of the values in its ItemsSource.

Update them to bind to a NEW property. Example:

   <ComboBox x:Name="cmbTaskList" 
            HorizontalAlignment="Left" 
            ItemsSource="{Binding MainListSource}"
            DisplayMemberPath="Description"
            SelectedValue="{Binding MainListSourceSelectedValue, Mode=TwoWay}"
            Margin="244,30,0,0" 
            VerticalAlignment="Top" 
            Width="185"/>

Then, set the NEW property (MainListSourceSelectedValue) when the SelectedSchedule property changes. Something like (in c#)

public MainList MainListSourceSelectedValue
{
    get { return _mainListSourceSelectedValue; }
    set
    {
        if (_mainListSourceSelectedValue == value) return; 
        _mainListSourceSelectedValue = value;

        RaisePropertyChanged();
    }
}

public Schedule SelectedSchedule
{
    get { return _selectedSchedule; }
    set
    {          
        if (_selectedSchedule == value) return;
        _selectedSchedule = value;

        foreach (var mainListItem in MainList)
        {
            if (mainListItem.Description.equals(_selectedSchedule.ResourseList.Description))
            {
                MainListSourceSelectedValue = mainListItem;
                break;
            }
        }

        RaisePropertyChanged();
    }
}
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