Q:

NumericUpDown value binding

I have a problem.  How to bind a ItemsSource property to a NumericUpDown?  This way it does not work.  Thx! 
<DataGrid ItemsSource="{Binding Articles}">
    <DataGrid. Columns>
            <DataGridTemplateColumn MinWidth="100"
                                Header="Amount"
                                MaxWidth="{Binding MinWidth, RelativeSource={RelativeSource Self}}">
            <DataGridTemplateColumn. CellTemplate>
                <DataTemplate>
                    <mahApps:NumericUpDown Value="{Binding Amount, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}">
                        <i:Interaction. Triggers>
                            <i:EventTrigger EventName="ValueChanged">
                                <i:InvokeCommandAction CommandParameter="{Binding}"
                                                       Command="{Binding DataContext. RefreshValuesCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}" />
                            </i:EventTrigger>
                        </i:Interaction. Triggers>
                    </mahApps:NumericUpDown>
                </DataTemplate>
            </DataGridTemplateColumn. CellTemplate>
        </DataGridTemplateColumn>
    </DataGrid. Columns>
</DataGrid>

EDIT
FIRST: Cantidad (Spanish) = Amount (English)

A:

If the Amount property is defined in the same class as the Articles property you should bind to the DataContext (DataContext. Amount) of the DataGrid:
<mahApps:NumericUpDown Value="{Binding DataContext. Amount, UpdateSourceTrigger=PropertyChanged, 
    RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}">
    <i:Interaction. Triggers>
        <i:EventTrigger EventName="ValueChanged">
            <i:InvokeCommandAction CommandParameter="{Binding}"
                                   Command="{Binding DataContext. RefreshValuesCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}" />
        </i:EventTrigger>
    </i:Interaction. Triggers>
</mahApps:NumericUpDown>

If the Amount property is defined in the data object (Article or whatever you call it) class it is simply:
<mahApps:NumericUpDown Value="{Binding Amount}">

Edit: You should also set the UpdateSourceTrigger of the Binding to PropertyChanged:
<mahApps:NumericUpDown Value="{Binding Amount, UpdateSourceTrigger=PropertyChanged}" />

