One DataSource for multiple controls

Question

I have two ListBox in my winforms application, I assigne a datasource for both of them as follow:

private void MakeMeasurementUnits()
{
    var units = new List<MeasurementUnit>
                    {
                        new MeasurementUnit {Name = "Current", SiUnit = "A"},
                        new MeasurementUnit {Name = "Voltage", SiUnit = "V"},
                        new MeasurementUnit {Name = "Time", SiUnit = "s"},
                        new MeasurementUnit {Name = "Temprature", SiUnit = "°C"}
                    };

    lbxXunit.DataSource = units;
    lbxYunit.DataSource = units;
}

The strange thing is (or maybe because it is my first time!!), in the form when I click on items of one of these lisboxes, the same item in the second listbox gets selected as well. Is this a default behaviour? how to prevent this? If this is default behaviour, what is useful about it?

I found the quick remedy to be making two different datasources (same thing with another name)

Answer 1

The listbox seems to cache the binding source. This is default behavior. If you want to avoid this, the easy way is to create a copy of the list to bind to the second data source:

lbxXunit.DataSource = units;
lbxYunit.DataSource = units.ToList();

This is useful when you have multiple views of the same data and want to synchronize the selection of these items.

Answer 2

Yes, this is normal behaviour. It happens because the ListView control uses a BindingSource object to track the currently selected item. (A List has no way to track a selected item without a BindingSource.)

By default, a DataSource in a WinForms control uses a BindingSource created for it by the WinForms system itself.

You can read more about the BindingSource at: http://msdn.microsoft.com/en-us/library/system.windows.forms.bindingsource.aspx

There is an article here which might help too: http://blogs.msdn.com/b/bethmassi/archive/2007/09/19/binding-multiple-comboboxes-to-the-same-datasource.aspx

Answer 3

The behavior you have noted is the default/correct behavior for winforms controls. You can achieve what you are after by setting a new BindingContext for your second listbox control without creating a copy of your data source.

BindingContext

Answer 4

This is correct behaviour. The datasource management in WindowsForms keeps track of the selected item on control and manipulates binded data too.

The resolution you've found already: is assign 2 different data sources objects to these controls.