Hyper -V 2012-R2 Expanding VHDX for VM did not expand the current file size
Increasing the vhdx doesn't increase the volume size inside the vm. So when you look at the c: drive size in the vm it will not change.
You need to open disk management and expand the volume to be the size of the vhdx. This won't instantly increase the file size on the host but it will show the extra available free space.
This link explains how to expand the volume in Windows 7 https://technet.microsoft.com/en-us/library/cc771473.aspx#BKMK_CMD