CODEWITHSUNDEEP
wpfmvvmbinding
Nicefsf
Nicefsf

Reputation: 140

Combobox SelectionChanged event binding

I have following xaml:

<DataGridTemplateColumn Header="123">
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Role}"/>
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>
<DataGridTemplateColumn.CellEditingTemplate>
    <DataTemplate>
        <ComboBox ItemsSource="{Binding Path=DataContext.Roles, 
                  RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGrid}}}">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="SelectionChanged">
                    <i:InvokeCommandAction Command="{Binding Path = DataContext.UpdateUserCommand}" /> // bind fails there
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </ComboBox>
    </DataTemplate>
</DataGridTemplateColumn.CellEditingTemplate>
</DataGridTemplateColumn>

The problem is that my command is not running on change, but if move combobox definition out of datagrid, my command is firing successfully. Seems like my bindging wrong, but i can't figure out what's wrong.

Upvotes: 1

Views: 580

Answers (2)

Clemens
Clemens

Reputation: 128061

Just bind the ComboBox's SelectedItem property to a SelectedRole property in your view model.

In order to run an async action when the view model property changes, just attach an async PropertyChanged event handler in the view model:

public class ViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public ViewModel()
    {
        PropertyChanged += async (s, e) =>
        {
            if (e.PropertyName == nameof(SelectedRole))
            {
                await SomeAsyncAction();
            }
        };
    }

    private Role selectedRole;

    public Role SelectedRole
    {
        get { return selectedRole; }
        set
        {
            selectedRole = value;
            PropertyChanged?.Invoke(this,
                new PropertyChangedEventArgs(nameof(SelectedRole)));
        }
    }

    private async Task SomeAsyncAction()
    {
        ...
    }
}

Upvotes: 1

Dean Chalk
Dean Chalk

Reputation: 20461

You could try this (not 100% sure it'll work because cannot see all of your code)

<i:InvokeCommandAction Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGrid}, Path=DataContext.UpdateUserCommand}" />

Upvotes: 0

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