Look at your code:
Books language = new Books()
{
Language = txtlanguage.Text.Trim(),
};
List<Books> l = modle1.GetBookbylanguage(language);
DataList1.DataSource = language;
Books is not a class that implements IListSource or IEnumerable - did you mean to declare
language
as a
OnlinebookCollection
instead? Or perhaps use
l
as your datasource?