I hope what you are trying to do is insert the objects in the data table (which probably are returned from a query) in to a List.
public List
Just saw your addition to the question! I can't understand why you try to generate a list if your intention is just to display the data in a gird view, which you can do in a single line!!!
List obj = new List();
DataTable dt = new DataTable();
dt.Columns.Add("ID");
dt.Columns.Add("Name");
dt.Rows.Add("1", "AAA");
dt.Rows.Add("2", "BBB");
dt.Rows.Add("3", "CCC");
dataGridView1.DataSource = dt; // THIS IS ALL U NEED! Just bind the DataTable to the grid as data source!