Question

I have a DataGrid in WPF (a class that extends DataGrid), and I would like to edit the items in it. But of course I am getting the following error:

Operation is not valid while ItemsSource is in use. 
Access and modify elements with ItemsControl.ItemsSource instead.

I have tried changing the itemsSource of the DataGrid, and then adding the items, but I still get the same error. Something like:

public class MyDG:DataGrid{

    public void add(){
        List<TimesheetRecord> records = new List<TimesheetRecord>();

        foreach(TimesheetRecord rec in this.Items){
            records.Add(rec);
        }

        //DO SOME STUFF, ADD MORE ITEMS TO records

        ItemCollection col = this.Items;
        this.ItemsSource = records;
        col.Clear();

       foreach(TimesheetRecord rec in records){
            col.add(red);//exception thrown here
        }

        this.ItemsSource = col;
    }

}

I don’t understand why I am getting that error, when I have already changed the itemsSource to a different list…?

I can’t (easily) add the items to the list which is originally bound as the itemsSource, because that list exists in a different class. Would it be best for me to just have a global variable in the MyDG class that is List<TimesheetRecord> myItems = new List<TimesheetRecord>(); and then in the constructor for MyDG go this.ItemsSource = myItems

Or do you have any other suggestions how I should go about doing this? I am open to anything, as this is the first time I have used databinding, so I am probably doing something wrong…

Answer 1

Decalre records collection as:

ObservableCollection<TimesheetRecord> records = new ObservableCollection<TimesheetRecord>();

and keep it data-bound to the DataGrid. Manipulate records collection as needed, data binding will take care of keeping UI in sync with the collection.