关于Expression<Func<T,bool>>表达式目录树的形式的强类型 lambda 表达式的拼接

当前在封装类EF的Where条件的表达式的解析逻辑，遇到的问题是：运用过程中可能需要将复杂的条件在不同的处理逻辑中Expression表达式进行拼接。

针对于遇到的问题写了示例进行记录，主要为了能够将Lambda表达式转为可执行的SQL语句，例子如下：

（相关的Lambda表达式转为SQL语句的整理待有空的时候再整理，这边先记录一下表达式的拼接）

            // f or f2 or f3
            Expression<Func<SimplifyClass, bool>> f = SC => SC.id > 0 && string.IsNullOrEmpty(SC.name);
            Expression<Func<SimplifyClass, bool>> f2 = SC => SC.sourcename != "AA" && SC.text == "CC";
            Expression<Func<SimplifyClass, bool>> f3 = SC => SC.sourcename.Contains("D");

            ParameterExpression pp = Expression.Parameter(typeof(SimplifyClass), "SC");
            MemberExpression fleftL = Expression.Property(pp, typeof(SimplifyClass).GetProperty("id"));
            ConstantExpression fleftR = Expression.Constant(0);
            BinaryExpression where1 = Expression.LessThan(fleftR, fleftL);

            MemberExpression frightR = Expression.Property(pp, typeof(SimplifyClass).GetProperty("name"));
            MethodCallExpression where2 = Expression.Call(typeof(string).GetMethod("IsNullOrEmpty"), frightR);
            where1 = Expression.And(where1, where2);

            MemberExpression f2leftL = Expression.Property(pp, typeof(SimplifyClass).GetProperty("sourcename"));
            ConstantExpression f2leftR = Expression.Constant("AA");
            BinaryExpression where3 = Expression.NotEqual(f2leftL, f2leftR);

            MemberExpression f2rightL = Expression.Property(pp, typeof(SimplifyClass).GetProperty("text"));
            ConstantExpression f2rightR = Expression.Constant("CC");
            BinaryExpression where4 = Expression.Equal(f2leftL, f2rightR);
            where3 = Expression.And(where3, where4);
            where1 = Expression.Or(where1, where3);

            MemberExpression f3leftR = Expression.Property(pp, typeof(SimplifyClass).GetProperty("sourcename"));
            ConstantExpression f3rightR = Expression.Constant("D");
            MethodCallExpression where5 = Expression.Call(f3leftR, typeof(string).GetMethod("Contains"), f3rightR);
            where1 = Expression.Or(where1, where5);

            Expression<Func<SimplifyClass, bool>> lambda = Expression.Lambda<Func<SimplifyClass, bool>>(where1, pp);
            //lambda转为SQL语句为：((@P0 < [id]) AND (ISNULL([name],'')<>'')) OR (([sourcename] <> @P1) AND ([text] = @P2)) OR ([sourcename] LIKE '%D%')