ことに details

fun + to my surprise/regret/delight, X — fronts a reaction word to comment on the clause that follows

tanoshii koto ni

to my surprise/regret/delight, X — fronts a reaction word to comment on the clause that follows

驚おどろいたことに、彼かれは試験しけんに一発いっぱつで合格ごうかくした。

odoroita koto ni, kare wa shiken ni ippatsu de goukaku shita.

To my surprise, he passed the exam on his very first try. neutral

意外いがいなことに、あいつ、ちゃんと約束やくそく守まもったんだよ。

igai na koto ni, aitsu, chanto yakusoku mamotta n da yo.

Surprisingly, that guy actually kept his promise! casual

Examples

to my surprise/regret/delight, X — fronts a reaction word to frame the whole clause that follows as unexpected or notable

驚おどろいたことに、彼かれは試験しけんに一発いっぱつで合格ごうかくした。

odoroita koto ni, kare wa shiken ni ippatsu de goukaku shita.

To my surprise, he passed the exam on his very first try. neutral

意外いがいなことに、あいつ、ちゃんと約束やくそく守まもったんだよ。

igai na koto ni, aitsu, chanto yakusoku mamotta n da yo.

Surprisingly, that guy actually kept his promise! casual

嬉うれしいことに、雨あめがやんで、無事ぶじに運動会うんどうかいが行おこなわれた。

ureshii koto ni, ame ga yande, buji ni undoukai ga okonawareta.

Happily, the rain let up and the sports day went ahead without a hitch. neutral

幸さいわいなことに、大おおきな被害ひがいはございませんでした。

saiwai na koto ni, ooki na higai wa gozaimasen deshita.

Fortunately, there was no major damage. formal

限かぎられた反応はんのう動詞どうしのた形けい＋ことに（驚おどろいた・困こまった・呆あきれた）attaches to verb stem (special attachment)
{I}ことにattaches to i-adjective
{NA-stem}なことにattaches to na-adjective

てならない
Both intensify an emotion word, but ことに fronts the feeling as commentary on a SEPARATE clause that follows (驚おどろいたことに、彼かれは来こなかった — the surprise stands outside the reported event), while てならない makes the feeling itself the sentence's own main predicate (心配しんぱいでならない — the worry IS what's being said).

ことになる
The identical fragment ことに opens both, but here it is a bare noun こと＋に marking the whole clause as a fronted comment (残念ざんねんなことに), while ことになる／ことにする attach straight after a VERB to report a decision or arrangement (延期えんきすることになった) — skim past what precedes ことに and "surprisingly" reads as "it was decided."
ことか
Same こと, unrelated jobs — ことか closes a sentence as a rhetorical exclamation on the clause just stated (どれだけ嬉うれしかったことか), while ことに opens a sentence, fronting a feeling word to comment on the clause that follows (嬉うれしいことに、合格ごうかくした) — one wraps a sentence up, the other winds one up.

no other patterns in this meaning class yet