Delete row from two sql tables that join together

Revision 1
There are two tables:

Table1 : UserID Name Job
Table2 : BookID Book Car UserID

I load these two tables in one wpf datagrid:

da.SelectCommand = new SqlCommand("select Table1.UserID, Table1.Name, Table1.Job, Table2.Book, Table2.Car from Table1 inner join Table2 on Table1.UserID = Table2.UserID");

I want to delete one row from Table2 by DataGrid:

SqlCommand com = new SqlCommand("delete from Table2 where BookID=@BookID)",con);

but not work,

How can I do it?