Question

I have interface IDoc and an abstract class that implements it named Doc. I then have a class named BookDoc that inherits from Doc and another class JournalDoc that also inherits from Doc.

Now what I would like to do is bind either a BindingList<BookDoc> or BindingList<JournalDoc> to a custom DataGridView. I then want to be able to access an Errors property the they both inherit from the Doc class.

semi working Example:

var dataSource = this.DataSource as BindingSource;

BindingList<BookDoc> tempBookDocs = dataSource.DataSource as BindingList<BookDoc>;

var Docs = new List<IDoc>();

foreach (var tempDoc in tempBookDocs)
{
    Docs.Add(tempDoc);
}

The above example works and i get a list of Docs that is populated and i can access the Errors property but still have to hard code the type of list that was originally bound.

What i would like to do is something like this though I’m not sure it is possible.

var dataSource = this.DataSource as BindingSource;

BindingList<Doc> Docs = dataSource.DataSource as BindingList<Doc>;

This gives me a null Docs list though.

Answer 1

If you’re using .NET 4.0, you can take advantage of covariance using IEnumarable<>:

IEnumarable<Doc> tempBookDocs = dataSource.DataSource as IEnumarable<Doc>;

var Docs = new List<IDoc>();

foreach (var tempDoc in tempBookDocs)
{
    Docs.Add(tempDoc);
}

If you’re using .NET 3.5, you can use LINQ OfType extension method:

IEnumarable<Doc> myDocs = ((IEnumarable)dataSource.DataSource).OfType<Doc>();

var Docs = new List<IDoc>();

foreach (var tempDoc in myDocs)
{
    Docs.Add(tempDoc);
}