join问题

[lihong1232]

    public IQueryable<T1, T2, T3> Join<E1, E2>(Expression<Func<E1, E2, bool>> expression, JoinType join = JoinType.Inner) where E1 : class where E2 : class
    {
        var onExpression = ExpressionUtil.BuildExpression(expression, _param, _prefix, false);
        var table1Name = EntityUtil.GetTable<E1>().TableName;
        var table2Name = EntityUtil.GetTable<E2>().TableName;
        var joinType = string.Format("{0} JOIN", join.ToString().ToUpper());
        if (_tables.Count == 0)
        {
            _tables.Add(table1Name);
            _tables.Add(table2Name);
            Join(string.Format("{0} {1} {2} ON {3}", table1Name, joinType, table2Name, onExpression));
        }
        else if (_tables.Exists(a => table1Name == a))
        {
            _tables.Add(table2Name);
            Join(string.Format("{0} {1} ON {2}", joinType, table2Name, onExpression));
        }
        else
        {
            _tables.Add(table1Name);
            Join(string.Format("{0} {1} ON {2}", joinType, table1Name, onExpression));
        }
        return this;
    }

T1, T2, T3 三个实体 ，为什么表达式只有E1, E2两个参数，不应该有个E3吗?不然E3的表关联关系怎么表达呢？

[soul-soft]

通过Join两次就能解决