Why does var not work on DataGridViewSelectedRowCollectoin

Question

I am interestend in the reason why the var keyword does not work properlyin a foreach-loop on the DataGridViewSelectedRowCollection.

ex1:

var selectedRows = MyDataGridView.SelectedRows;
foreach (var row in selectedRows)
        { 
            var foo = row.DataBoundItem;
            _bindingSource.Remove(foo);
        }

ex1 the type of 'row' is object. Why is it not of type 'DataGridViewRow'

ex2 works perfectly:

var selectedRows = MyDataGridView.SelectedRows;
foreach (DataGridViewRow row in selectedRows)
        { 
            var foo = row.DataBoundItem;
            _bindingSource.Remove(foo);
        }

also if I access the item of the collection directly it works:

var selectedRows = MyDataGridView.SelectedRows;
var foo = selectedRows[0];
var bar = foo.GetType().Name; // bar == DataGridViewRow

I am interested in the reason why this happens.

Thanks in advance

Answer 1

The DataGridView.SelectedRows Property returns a DataGridViewSelectedRowCollection . The type declaration for DataGridViewSelectedRowCollection class is:

public class DataGridViewSelectedRowCollection : BaseCollection, 
    IList, ICollection, IEnumerable

Notice that the class implements IEnumerable , but not IEnumerable<DataGridViewRow> . The IEnumerator.Current Property that is returned as the item of a foreach loop is of type System.Object . Therefore, the IDE/compiler is assigning var row an object type and technically the type inference is working as specified.

The reason var foo = selectedRows[0]; works , is that the DataGridViewSelectedRowCollection.Item Property returned by the C# indexer is typed as a DataGridViewRow, so the type inference picks that up.