How do I combat Necrons?

After another humiliating defeat at the hands of yet another Necron army I find myself caught between two possible courses of action. The first, it to learn from my mistakes and field more units to combat Necrons. The second option however, is to just not fight Necrons ever again and eliminate the possibility of losing to them ever again.

My opponent was equipped with the following:

Necron Lord x 1
Immortals x 10
Necron Warriors x 10
Necron Warriors x 10
Annihilation Barge x 1
Canoptek Wraiths x 5
Scarabs x 4
Canoptek Spider x 1
Tomb Blades x 6
Destroyer Squad x 3

Whilst I was equipped with:

Company Master x 1
Librarian x 1
Tactical Squad x 10
Deathwing Knights x 5
Deathwing Terminators (Storm Bolters) x 5
Dreadnought with Lascannon
Devastator Squad with Plasma cannons x 5
Ravenwing Command Squad x 3
Ravenwing Attack Squad x 3

The game began with almost no cover due to no other tables being available, what little cover there was I positioned neutrally along with our objective markers. I got initiative and went first, I moved in order to position my troops in the best positions available to gain objectives whilst seeking what little cover was possible.

I lost the game spectacularly due to objectives being constantly contested and my Ravenwing never making it to the objective I sent them to. Secondly the casualty rate was catastrophic due to the fact that my troops were completely annihilated.

Casualties:

Necron

6 Necrons Warriors
1 Canoptek Wraith
1 Scarab (Later rebuild by the Canoptek Spider)

Dark Angels

3 Ravenwing Command
3 Ravenwing Attack Squadron
5 Devastator Squad
1 Dreadnought
5 Deathwing Terminators
4 Tactical Squad

My Ravenwing were gunned down before they could even make it to cover despite my opening salvo taking out the majority of the Necron Warriors. My Deathwing Knights never made it to the battle due to deep strike mishap and my Terminators suffered a mishap and were positioned in perfect range of the Immortals and Necron Warriors. My Tactical Squad were set upon by Canoptek Wraiths and I only held out due to my psyker gaining an invulnerable save on the Perils of the Warp table. My Devastator squad however were wiped out by the Destroyer Squad and my Dreadnought fell to scarabs.

It seems impossible to win against Necrons so I ask you all as experienced players. How the hell do I fight Necrons and stand any sort of chance of winning?