How to Casting DataSource to List?

Question

I have the following method that load products on a DataGridView

private void LoadProducts(List<Product> products)
{
    Source.DataSource = products;  // Source is BindingSource
    ProductsDataGrid.DataSource = Source;
}

And now I'm trying to give me back to save them as shows below.

private void SaveAll()
{
   Repository repository = Repository.Instance;
   List<object> products = (List<object>)Source.DataSource; 
   Console.WriteLine("Este es el número {0}", products.Count);
   repository.SaveAll<Product>(products);
   notificacionLbl.Visible = false;
}

But I get an InvalidCastException on this line:

List<object> products = (List<object>)Source.DataSource;

So how can I cast the DataSource to an List?

What exactly does the exception say? – svick Jan 11 '13 at 14:17 — svick, Jan 11 '13 at 14:17

Dave Bish · Accepted Answer · 2013-01-11T14:49:14.883

24

You can't cast covariantly directly to List;

Either:

List<Product> products = (List<Product>)Source.DataSource;

or:

List<Object> products = ((List<Product>)Source.DataSource).Cast<object>().ToList();

edited Jan 11 '13 at 14:49

answered Jan 11 '13 at 14:20

Dave Bish

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For Line `List – Cristhian Boujon Jan 11 '13 at 14:30
You need a .ToList() at the end, my bad! – Dave Bish Jan 11 '13 at 14:49

Tilak · Answer 2 · 2013-01-11T16:33:00.710

6

So how can I cast the DataSource to an List?

You have plenty of options

var products = (List<Product>)Source.DataSource; // products if of type List<Product>

or

 List<Object> products = ((IEnumerable)Source.DataSource).Cast<object>().ToList();

or

List<Object>  products = ((IEnumerable)Source.DataSource).OfType<object>().ToList();

or

List<Object> products = new List<Object>();
((IEnumerable)Source.DataSource).AsEnumerable().ToList().ForEach( x => products.Add( (object)x));

edited Jan 11 '13 at 16:33

answered Jan 11 '13 at 14:25

Tilak

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`DataSource` doesn't implement `IEnumerable`, so you'll need to cast it to that first. – Servy Jan 11 '13 at 15:05
Same problem. `AsEnumerable` is an extension method of `IEnumerable`, not `object`. – Servy Jan 11 '13 at 15:09
Removed the last way. I was wondering How `Cast<>` can work and `AsEnumerable` cannot, while both accept `IEnumerable` as input? – Tilak Jan 11 '13 at 15:16
Neither can work, that's what I'm saying. You need to do `((IEnumerable)Source.DataSource).Cast – Servy Jan 11 '13 at 16:29

score 3 · Answer 3 · answered Jan 11 '13 at 14:19

3

Your List ist of type List<Product> which is different from List<object>. Try to cast to List<Product>

answered Jan 11 '13 at 14:19

CubeSchrauber

1,199
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score 0 · Answer 4 · edited Feb 13 '18 at 09:50

0

Convining the answers This is my solution:

private void SaveAll()
{
    Repository repository = Repository.Instance;
    List<Product> products = (List<Product>)Source.DataSource;
    IEnumerable<object> objects = products.Cast<object>();
    repository.SaveAll<Product>(objects.ToList<object>());
    notificacionLbl.Visible = false;
}

I accept constructive criticisms.

edited Feb 13 '18 at 09:50

daniele3004

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answered Jan 11 '13 at 14:39

Cristhian Boujon

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what exactly is the input parameter type of SaveAll? are you sure you need a List – Eren Ersönmez Jan 11 '13 at 14:43
The idea is that `SaveAll(List – Cristhian Boujon Jan 11 '13 at 14:47
1

then it would make more sense if the signature is `SaveAll(List ...`, or even better `SaveAll(IEnumerable ...`. – Eren Ersönmez Jan 11 '13 at 14:51

How to Casting DataSource to List?

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