昨日はディナーに招待してくれてありがとう。
この間は楽しかったよ、ありがとう。
のような表現はどう言えばいいのでしょうか？
どなたか教えて下さい。

Thank you for the dinner last night. I had so much fun.

or I enjoyed the dinner very much.

or It was a slice of bread! ----slice of bread=fun,good time
(sometimes we would say "It was a loaf of bread" or "it was a bakery" :)
　

Ｋｉｋｉさん
教えていただいてありがとうございます！
さっそく使わせていただきます! 　

We would NEVER say "It was a slice of bread", "It was a loaf of bread", or "It was a bakery". The correct idiom is: "It was a slice." And, the original meaning was that something was easy to do. 　

Thank you for the correction!
and Sorry to Topi-nushi san(><) 　

As far as I’m concerned, Hans’ suggestion, "it was a slice," is no more correct than Kiki’s suggestion, "it was a slice of bread." In 28 years of living in North America I have never heard either expression. Of course, that doesn’t mean either is incorrect; I just don’t think there is any need for Kiki to apologize.　両方聞いたことがないからKikiさんが謝る必要わけないと思いますが。

「非常に簡単なこと」という意味を表す「a piece of cake」という熟語が一般的に使われているけれど。
（例）
A: How was the yesterday’s test?（昨日のテストはどうでしたか？）
B: It was a piece of cake. (非常に簡単だったよ。）

かなりトピずれになっていますが。 　

Thank you,田舎ボーイsan for saying(writing?)that I didn’t need to apologize. But I was wrong. I remembered incorrectly.
My husband told me you don’t say it was a slice of bread. just say it was a slice. and also he told me this is kind of inside joke between our group especially "loaf of bread" and "whole bakery"part. so no wonder you’ve never heard of it.
I was very embarrassed when I found out I was wrong here. I felt I shouldn’t have said anything in first place but your Res made me feel better. Thanks again. and sorry for the confusion!