Question

I am writing WPF application using MVVM. I have ObservableCollection of my items:

public ObservableCollection<VarValue> Values;

public class VarValue: INotifyPropertyChanging, INotifyPropertyChanged
{
    public double value
    {
        get
        {
            return this._value;
        }
        set
        {
            if (this._value != value)
            {
                this.OnvalueChanging(value);
                this.SendPropertyChanging();
                this._value = value;
                this.SendPropertyChanged("value");
                this.OnvalueChanged();
            }
        }
    }
}

which is binded to dataGrid1:

dataGrid1.ItemsSource = Values;

<DataGrid EnableColumnVirtualization="true" EnableRowVirtualization="true" Name="dataGrid1" DockPanel.Dock="Top" AutoGenerateColumns="False" Height="120" Width="Auto" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserResizeRows="False" CanUserSortColumns="False" SelectionUnit="Cell">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate><TextBlock Text='{Binding Values.value}'/></DataTemplate></DataGridTemplateColumn.CellTemplate>
    <DataGridTemplateColumn.CellEditingTemplate>
        <DataTemplate><TextBox Text='{Binding Values.value, Mode=TwoWay}'/></DataTemplate></DataGridTemplateColumn.CellEditingTemplate>
</DataGrid>

When user edits dataGrid1 cell, I need to create new VarValue object, and insert it into existing collection. For example:

• datagrid contains one cell with value=1
• user changes it to value=2
• now in table must be two cells: with 1 and 2 values.

How can i achieve that?

Answer 1

You could create a wrapper around VarValue and bind it in your grid:

public class VarValueVM : INotifyPropertyChanged
{
    private VarValue _value;
    private ObservableCollection<VarValueVM> _values;

    public VarValueVM(VarValue value, ObservableCollection<VarValueVM> values)
    {
        _value = value;
        _values = values;
    }

    public double value
    {
        get
        {
            return _value.value;
        }
        set
        {
            if (this._value.value != value)
            {
                _values.Add(new VarValueVM(new VarValue() { value = value }, _values));
                this.SendPropertyChanged("value"); //In order to tell the grid that value did not change finally...
            }
        }
    }
}