如何在LINQ-to-SQL中编写此交叉应用查询？

I have the following tables:

我有以下表格：

create table TableA (
    Id int primary key identity,
    Key int not null
)

create table TableB (
    Id int primary key identity,
    TableA_Id int not null foreign key references TableA(Id),
    Value varchar(80) not null
)
create