And i guess the いっしょに行く part is implied. But what if I wanted to explicitly include it for the sake of learning. I have read that adding the の particle can convert a verb to a noun. So is the following sentence grammatically correct.
(I am aware i could get away with 行きましょうか but please help me out with the above sentence)
I don’t think there is any such implication. That to me would imply you had to go to the concert together (as in you shared a ride together, though I could be wrong on this). Whereas いっしょにいかがですか is more like asking simply if they’ll join you at the concert, but you could go towards and arrive separately at the event. Though obviously in English you could translate both as 'How about going to the concert with me?"
If you say like this, you’re offering someone else to join you at a concert that you will attend. This kind of implies you’ll end up at the concert even if the other person declines the offer.
If you like to suggest to go to a concert you can simply ask:
(いっしょに) コンサートに行きましょうか or
I go with @Milgram, to me it feels more natural. In case you’d be very eager to go you can say:
(いっしょに) コンサートに行きましょうか。どうですか。…and make very happy smiling face so the other person gets the hint
In case you’re talking with a friend you can make it more casual… but I’m bad with casual japanese, sorry.
tl;tr: 「ごいっしょにいかがですか。」/「いっしょにどうですか。」=> “Would you like to join?”,「～するのはどうですか？」=> "Why not～?"
I like the following question (and response) on Japanese stackexchange because it is short, but I will give some more links to other articles as well since they don’t have examples with いっしょに.
will be the same. This seems to be supported by, for example weblio, where they have example sentence for 「ごいっしょにいかがですか。」 and 「いっしょにどうですか。」both saying "Would you like to join?" or slightly less formal “Do you want to join?”
A very nice and short summary in Japanese you may find on this blog post. It is for Japanese people who’d like to learn English, so they explain certain English grammar pattern and what it would mean in Japanese: Would you like some coffee? Would you like to join us?
=> in the 今回の英語 section they are describing the two patterns
In section 1-1 they give some examples when to use 「一緒にどう？」.
In section 1-2 they give some examples when to use 「~ない？/ ~ませんか。」. All the examples seem to have more casual Japanese expression.
In section 2 you’ll see an example for the「[noun] はどう？」pattern but I’ll give you one more article which might be better for that one…
This How about～ article is all about different patterns with 「どうですか？」and what they mean in English. They give lot’s of example sentences in English and what they mean in Japanese. They also talk about the 「～するのはどうですか？」pattern and translate it to 「Why not～?」.
=> So, if you say 「コンサート(いっしょ)に行くのはどうですか。」you’ll suggest to go to a concert together. …and you can probably shorten it to 「コンサートはどう？」in case the context already makes it clear that you’re talking about going there.
It kind of implies that going to the concert would be your preferred option but in case the other person says no you may offer to do something else.
I guess it is not perfect answer and definitely not easy one but I hope it gives you some help where to look