CODEWITHSUNDEEP
c#wpfdatagridobservablecollection
user2545071
user2545071

Reputation: 1410

ObservableCollection is null after remove item

Good day! I try to remove selected item from ObservableCollection, but after that- collection becomes null!

private void btDelParameter_Click(object sender, RoutedEventArgs e)
    {
        var selectedItem = dgParametrs.SelectedItem as Row;

        if (selectedItem != null)
        {


            if (_viewModel.ObjectViewNodel.RowInputColl != null)
            {
                if(_viewModel.ObjectViewModel.RowInputColl.Contains(selectedItem))
                    _viewModel.ObjectViewModel.RowInputColl.Remove(selectedItem); //after that RowInputColl is null!
            }
            else _viewModel.ObjectViewModel.RowInputColl = new ObservableCollection<Row>();


        }
    }

Some part of XAML code:

 <DataGrid AutoGenerateColumns="False" 
                          Name="dgParametrs"     

                              CanUserAddRows="False"
                              CanUserDeleteRows="False"
                              IsEnabled="True"
                              IsReadOnly="False"
                              SelectedItem="{Binding ObjectViewModel.RowInputColl,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
                          >
 ...

It is very strange for me,it works fine at last time.

Please, help me with that problem! What i should do, that collection does not becomes null after remove item!

Thank you!

SOLUTION: it was old code- so at that old code need to use SelectedItem. But, at now- i change SelectedItem to ItemsSource- and it works! Thank you!:)

Upvotes: 0

Views: 717

Answers (1)

Gaurav Sharma
Gaurav Sharma

Reputation: 586

I am slightly confused with you code looks. So from your Xaml code, I can see the you have binded SelectedItem to ObjectViewModel.RowInputColl. So I am assuming its an Item from a Collection

<DataGrid AutoGenerateColumns="False" 
                          Name="dgParametrs"
                              CanUserAddRows="False"
                              CanUserDeleteRows="False"
                              IsEnabled="True"
                              IsReadOnly="False"
                              *SelectedItem="{Binding ObjectViewModel.RowInputColl,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"*
                          >

But now, when I go to your C# code. You are trying to Remove from the same item you binded to SelectedItem ObjectViewNodel.RowInputColl. You need to Bind ItemsSource property to the collection and then create a selected Item property in your view model to bind to selected item. Then remove SelectedItem from collection.

var selectedItem = dgParametrs.SelectedItem as Row;

if (selectedItem != null)
{
    if (_viewModel.ObjectViewNodel.RowInputColl != null)
    {
        if(_viewModel.ObjectViewModel.RowInputColl.Contains(selectedItem))
            _viewModel.ObjectViewModel.RowInputColl.Remove(selectedItem); //after that RowInputColl is null!
    }
    else 
    {
        _viewModel.ObjectViewModel.RowInputColl = new ObservableCollection<Row>();
    }
}

Upvotes: 2

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