Combobox ItemSource not binding with data from ViewModel

Question

I have a Combobox:

<ComboBox   Height="23" 
            Name="DriveSelection" Width="120"
            ItemsSource="{Binding Path=FixedDrives}"
            DisplayMemberPath="fixedDrives"
            SelectedItem="{Binding Path=DriveSelection_SelectionChanged}"
            IsSynchronizedWithCurrentItem="True"/>

Here code for ItemsSource:

private ObservableCollection<DriveInfo> fixedDrives;
public ObservableCollection<DriveInfo> FixedDrives
{
    get
    {
        if(fixedDrives==null)
        {
           var query =
                from driveInfo in DriveInfo.GetDrives()
                //where driveInfo.DriveType == DriveType.Fixed
                select driveInfo;
           fixedDrives= new ObservableCollection<DriveInfo>(query);
           return fixedDrives;
        }

        return fixedDrives;
    }
}

and here event handler:

private void DriveSelection_SelectionChanged()
{
    if (page.DriveSelection.IsEnabled)
    {
        this.UpdatePathManager();
    }
}

I checked similiar questions like this one or this one and didnt find there any answers.

I know that ViewModel is bounded to View. Other binds to buttons etc are working.

After Updates:

private DriveInfo driveSelection;
public DriveInfo DriveSelection_SelectionChanged
{
    get
    {
        return driveSelection;
    }
    set
    {
        if (value == driveSelection) return;
        driveSelection = value; 
        NotifyOfPropertyChange(() => UpdatePathManager()); //UpdatePatchmanager is my function and it exists.
        //Notify... throws does not exists in currenct context
    }
}

XAML:

<ComboBox  Height="23" 
           Name="DriveSelection" 
           Width="120" 
           ItemsSource="{Binding Path=FixedDrives}" 
           DisplayMemberPath="Name" 
           SelectedItem="{Binding Path=DriveSelection_SelectionChanged}" 
           IsSynchronizedWithCurrentItem="True" />

and binding the ViewModel:

public PathSelectionPage()
{
    InitializeComponent();
    this.DataContext = new PathSelectionPageViewModel(this);
}

After all thouse updates Combobox is still without any options and its greyed out.

And NotifyOfPropertyChange is throwing does not exists in current context and:

class PathSelectionPageViewModel : ObservableObject, INavigable, INotifyPropertyChanged

Answer 1

DisplayMemberPath应该是DriveInfo类中的属性名称，而不是DisplayMemberPath="fixedDrives"而SelectedItem应该是DriveInfo类型的VM上的属性，而不是函数

Answer 2

Your DisplayMemberPath Should be a property of your Collection not the Collection Itself.

From this to:

 DisplayMemberPath="fixedDrives"

Something Like this:

<ComboBox Height="23" 
        Name="DriveSelection" Width="120"
        ItemsSource="{Binding Path=FixedDrives}"
        DisplayMemberPath="Property1"
        SelectedItem="Property"
        IsSynchronizedWithCurrentItem="True"/>

Answer 3

You don't need write event handler because it is nor MVVM way. You must write something like this

   <ComboBox Height="23" 
        Name="DriveSelection" Width="120"
        ItemsSource="{Binding Path=FixedDrives}"
        DisplayMemberPath="PropertyOfDriveInfo"
        SelectedItem="{Binding Path=SelectedInfo}" />

class ViewModel: INotifyPropertyChanged
{
    private ObservableCollection<DriveInfo> fixedDrives;
    public ObservableCollection<DriveInfo> FixedDrives
    {
        get
        {
            if(fixedDrives==null)
            {
               var query =
                from driveInfo in DriveInfo.GetDrives()
                //where driveInfo.DriveType == DriveType.Fixed
                select driveInfo;
               fixedDrives= new ObservableCollection<DriveInfo>(query);
               return fixedDrives;
            }
            return fixedDrives;
         }
    }

    private DriveInfo _selectedInfo
    public DriveInfo SelectedInfo
    {
        get { return _electedInfo; }
        set
        {
            if (value == _electedInfo) return;
            _selectedInfo= value;
            NotifyOfPropertyChange(() => SelectedInfo);//must be implemented
        }
    }
}