Tool evaluation criteria is very important for the success 
of Automation and it is done by the experts. Tool 
evaluation is part of the Test plan.

There are many factors to be considered for Tool evaluation.

1. What kind of projects needs automation?

i.  Automation is beneficial for long term projects.
ii. Projects with lots of functionality.
iii.Projects with lots of regression scenarios. 
iv. The application shoule be stable.
v.  There should be not be GUI changes.

Note: The application should be stable without any frequent 
GUI changes or else the automation scripts will fail.

2. When should be automation done?

A. Manual testing has to be done atleat once before 
automating the application. Manual testing would help in 
knowing the expecte results and actual results.

Note: This would help while creating check points in 
automation.

Once the above 2 questions conform with your project 
requirement for automation then tool evaluation criteria 
should consider:

i.  Project budget (As automation tools are very costly).
ii. Compatibility with the Application (Some tools need Add-
ins to be compatible with the application and to identify 
the objects).
iii. Number of licenses required.
iv.  Support given by the tool support team.
v.   Limitations and drawbacks of the tool.
vi.  Expereiced automation resources.

Regards,
Imthiyaz. Shaik

Thank you Imthiyaz.

Our organization is using UTP for .Net automation, you also 
can try . They have all the AddIns bundled with the 
product, so our company did not have to invest on AddIns 
separately.

http://www.sdtcorp.com/utp_solution.html