Do you think guys, that the purposes behind China's investment are to have shorter route to Arabian Sea and friendship that these two countries share?
Does anybody have the idea about the actual rationales behind this development?

Very beneficial for China, but since Pakistan is a cave man in front of China, I'd take the deal. What's the worst that can happen? China takes over Pakistan and we become the New Mexico of South Asia.

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For China it would provide a shorter, alternative route to major oil-producing countries than south east Asia’s strait of Malacca, an overcrowded, relatively shallow sea lane troubled by pirates.
For me nothing worst is happening. Best for both countries. Pakistan will also get benefits. Pakistan is independent country with strong army and whole world know this, so nothing to be worried.

yeh its really help to grow pakistan ........

Guys, the point to discuss was not to worry about it.
I think the purpose, for China, behind all this is far higher than just to have shorter route.
China is an emerging super power which have to supersede the America in this regard. Pakistan being a main ally of US in this region has been dependent on it since almost its inception. China is fully aware of all these facts that without independent Pakistan in all the walks of life, It can't lessen the influence of America from the region. The investment of $46 billion and export of 8 submarines to Pakistan would be the second step after the formation of Asian Infrastructure Investment Bank (AIIB) to diminish the influence of USA from the region.

Guys my detailed point of view regarding this is as under, please comment and let me know the weaknesses of this piece of writing.

Topic: "Game Changer - China's commiseration for Pakistan"

Since childhood, we have been brought up studying that Pakistan has an important strategic location in the region but practically it was never realized. As we were not fully aware of Pakistan’s geographic significance, our neighbours had too been underestimating us in this regard. Firstly, India’s top brass is often witnessed saying “Pakistan being a small territory has nothing to do with regional politics or strategy in large spectrum” and Afghanistan has given preference to India over Pakistan in several issues.
If we keenly observe the map of Asia and its contiguous continents, having three major actors of world polity the United States of America, the Russian Federation and the People's Republic of China in mind, we definitely have clear image of the strategic position that Pakistan has.
From its inception, Pakistan seemed strategically most critical country to USA and he longed to hold Pakistan to have Asia, Middle East, Eurasia and some parts of Africa under his influence and Uncle Sam has been successful in his mission. As discussed several times that Pakistan’s economy has been depending on foreign aid particularly from USA, Pakistan has been vulnerable to others’ interests. “If you aid it, it would be all yours”, USA’s policy towards Pakistan has been drawn on these very lines and it has been paying less and gaining a lot.
But now world’s polity is rapidly changing its shape as China is emerging as one of the major powers and Russia being a rival to USA too has been seeking to protect its interests in the region. Nevertheless China is an old friend of Pakistan, now there are seemingly other interests lying in the upcoming investment of $46 billion and export of eight submarines to Pakistan. China and Russia are so polite to Pakistan these days that it never happened ever before. Actually the reason behind this commiseration is that these two major actors of world politics are changing and adopting foreign strategic policy towards Islamabad for lessening the influence of USA from the region, and the period of next five to ten years would be proved as “game changer” for the region.
Developing Pakistan would be the second step of the immediate world political players after the formation of Asian Infrastructure Investment Bank (AIIB) that may alter the recent line of course.

China wants to exploit resources of Africa, so it can make iphones at cheaper cost and sell it to Americans. Pakistan would provide a shorter route to China.

We get to benefit from the trade route that crosses through our country.