I am thinking about buying a EVGA GeForce GTX 1050 Ti SC Gaming P/N: 04G-P4-6253-KR.
 
Can I use this card in my Dell Optiplex 790? I have a Thermaltake 600w power supply.
 
Thank You

Welcome to the Forum djnolan
I see why not but ask this same question over on Dell's Website.
This card has no Power Connector and you only need 300Watt PSU.
It would be based on your Motherboard and CPU.
http://www.dell.com/support/home/us/en/04/product-support/product/optiplex-790/drivers/advanced
Current Bios is A18 so make sure you update your Dell to this Bios.
Also your Dell comes only with AMD So knowing this you may have issues.
Chipset Being that they are Intel and not AMD Chipset you may be in luck.

I personally think it won't work. Only one way to find out.