Question

Having a weird problem with two WPF datagrids bound to separate ObservableCollections.

Here’s my XAML:

<Grid Name="gridShifts">
<Grid.ColumnDefinitions>
    <ColumnDefinition/>
    <ColumnDefinition/>
</Grid.ColumnDefinitions>
    <Custom:C1DataGrid Name="dgShift1"
                       HorizontalAlignment="Left" AutoGenerateColumns="False" CanUserAddRows="False" CanUserRemoveRows="False" CanUserReorderColumns="False" Grid.Column="0">
        <Custom:C1DataGrid.Columns>
            <Custom:DataGridTextColumn Binding="{Binding Path=Type, Mode=TwoWay}" IsReadOnly="True"  Header="Work Center"/>
            <Custom:DataGridTextColumn Binding="{Binding Path=RegularSkill, Mode=TwoWay }" Header="Personnel"/>
        </Custom:C1DataGrid.Columns>
    </Custom:C1DataGrid>
    <Custom:C1DataGrid Name="dgShift2"
                       HorizontalAlignment="Left" AutoGenerateColumns="False" CanUserAddRows="False" CanUserRemoveRows="False" CanUserReorderColumns="False" Grid.Column="1">
        <Custom:C1DataGrid.Columns>
            <Custom:DataGridTextColumn Binding="{Binding Path=Type, Mode=TwoWay}" IsReadOnly="True"  Header="Work Center"/>
            <Custom:DataGridTextColumn Binding="{Binding Path=RegularSkill, Mode=TwoWay }" Header="Personnel"/>
        </Custom:C1DataGrid.Columns>
    </Custom:C1DataGrid>
</Grid>

And here’s my code behind:

public partial class MainWindow : Window
{
    AMMData.Manpower mp = new AMMData.Manpower();

    public MainWindow()
    {
        InitializeComponent();

        gridShifts.DataContext = mp;
        dgShift1.ItemsSource = mp.WorkShifts[0].WCList;
        dgShift2.ItemsSource = mp.WorkShifts[1].WCList;

    }
}

EDIT: Here is the Manpower class:

public enum WCSpecialty
{
    Indirect,
    Airframes,
    AviationLifeSupport,
    PeriodicMaintenance,
    Electronics,
    Electrical_Instruments,
    Armaments,
    Reconnaissance,
    Line,
    NA
}

public class Manpower : ComponentDataWrapper
{
    #region Private Properties

    private ObservableCollection<WCCollection> workShifts = new ObservableCollection<WCCollection>();

    #endregion

    #region Public Properties

    public ObservableCollection<WCCollection> WorkShifts { set { workShifts = value; NotifyPropertyChanged("WorkShifts"); } get { return workShifts; } }

    #endregion


    public Manpower()
    {
        Name = "New Work Center Structure";
        Description = "New Work Center Personnel Description";
        LastChanged = System.DateTime.Now;

        var wcc1 = new AMMData.WCCollection();
        var wcc2 = new AMMData.WCCollection();

        var wc1 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Indirect, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc2 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Airframes, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc3 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.AviationLifeSupport, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc4 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.PeriodicMaintenance, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc5 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Electronics, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc6 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Electrical_Instruments, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc7 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Armaments, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc8 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Reconnaissance, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc9 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.Line, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };
        var wc10 = new AMMData.WorkCenter { Type = AMMData.WCSpecialty.NA, RegularSkill = 0, MedSkill = 999, HighSkill = 999 };

        wcc1.WCList.Add(wc1);
        wcc1.WCList.Add(wc2);
        wcc1.WCList.Add(wc3);
        wcc1.WCList.Add(wc4);
        wcc1.WCList.Add(wc5);
        wcc1.WCList.Add(wc6);
        wcc1.WCList.Add(wc7);
        wcc1.WCList.Add(wc8);
        wcc1.WCList.Add(wc9);
        wcc1.WCList.Add(wc10);

        wcc2.WCList.Add(wc1);
        wcc2.WCList.Add(wc2);
        wcc2.WCList.Add(wc3);
        wcc2.WCList.Add(wc4);
        wcc2.WCList.Add(wc5);
        wcc2.WCList.Add(wc6);
        wcc2.WCList.Add(wc7);
        wcc2.WCList.Add(wc8);
        wcc2.WCList.Add(wc9);
        wcc2.WCList.Add(wc10);

        WorkShifts.Add(wcc1);
        WorkShifts.Add(wcc2);

    }
}

public class WCCollection : ComponentDataWrapper
{
    private ObservableCollection<WorkCenter> wcList = new ObservableCollection<WorkCenter>();

    public ObservableCollection<WorkCenter> WCList { set { wcList = value; NotifyPropertyChanged("WCList"); } get { return wcList; } }
}

    public class WorkCenter : ComponentDataWrapper
{
    #region private

    private WCSpecialty type;
    private int regularSkill;
    private int highSkill;
    private int medSkill;

    #endregion

    #region public

    public WCSpecialty Type { set { type = value; NotifyPropertyChanged("Type"); } get { return type; } }
    public int RegularSkill { set { regularSkill = value; NotifyPropertyChanged("RegularSkill"); } get { return regularSkill; } }
    public int HighSkill { set { highSkill = value; NotifyPropertyChanged("HighSkill"); } get { return highSkill; } }
    public int MedSkill { set { medSkill = value; NotifyPropertyChanged("MedSkill"); } get { return medSkill; } }

    public int RegularWholePeople { get { return regularSkill / 10; } }

    #endregion
}

My problem is that when I edit one datagrid, the other’s values also change. I’ve tried setting the datacontext for both grids to their respective ObservableCollections, but the same thing happens. I feel like I’m moderately familiar with how WPF databinding works at this point, but I’m completely stumped on this issue. Thanks for any help.

Answer 1

It looks like your items are being added to your ObservableCollections by reference, not by value.

This means both collections contain a reference to the same object in memory, so updating an object in one collection is actually updating the single object reference, which causes the other collection to update as well