>Hi,
>I set the code in the Addnew button click event.
>theBindingSource.AllowNew = false
>
>but it return an error that "Item cannot be added to a read-only or fixed-size list."

Are you sure that that is the line throwing the exception rather than the attempt to actually add an item? The documentation only mentions exceptions when setting the AllowNew property to true :http://msdn.microsoft.com/en-us/library/system.windows.forms.bindingsource.allownew.aspx