I don't see a hook here to click your ads. If I'm looking for a C# programmer, why would I choose you? What's the incentive to click your ad?
> a) We are now in bad times to sell programming.
I don't think there's any bad times to sell anything. The demand may be lower but you are looking to attract those looking for your products or services.
You may want to look over your keywords. Some negatives may help such as "job" for those looking for jobs as developers.
> c) Are you sure programming contractors click in ads to rent a coder?
That could be part of the problem. Another reason to focus on keywords for those looking to hire as opposed to those hiring. I'm not sure that the hirers will search that much, they'll use other methods.
I'm also thinking that few hirers will know they want a C# or other language programmer. They know they want or need A programmer but not specifically say a VB programmer, especially a small business. If small businesses are your target, you'll need to rethink your strategy.
I would not use the content network for this.
There was mentioned in one post of ad blindness. Could be but I highly doubt it in this case. What I do suspect however is that you need to be in the top three ads. It's more a right-hand side blindness.