I am in manual testing from last 5+ years and having a sound experience in it. Now I want to switch in automation testing and want to start with Selenium.
I don't have any programming experience or knowledge in either Java and C#.
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Sign up to join this communityRobotframework-seleniumLibrary is a good choice, if you want to get involved with less coding and more test automation.
Python or Java may be a good choice to start with, if you want to focus on test automation.
Python is widely considered best language for beginners, much simpler than Java or C#.
Once you understand programming in Python, it will be easier to learn other languages (and you will understand why Python is easier).
But before all this, you should learn how to use Google. This exact question is asked on this exact forum every week.
Everything has a context.
Will you join or start an automation project? Follow the language of this project.
Do you want a fast learning curve on the basics of programming and automation? Take a look in Python; do a Codeacademy-like course and play with each entry on the Learn X in Y Minutes site - try run and change things to see what happens. After that, learn the Page Object pattern auto-critically, always checking if you are building something extendable, using good OO programming. The Python tutorials and courses lack sometimes this sort of critic.
Do you want to look at the market? Java is more used than C# by big companies, because they have dev people used to Java - Javascript is closely used, depending on the region you are. The con here is that the community for automation in these language is not so strong.
Do you want to experiment with dozen of open source tools built-upon Selenium? Take a look at Ruby; the Cucumber environment is extremely active and the integration with Rails is the focus. Javascript's community is as active as Ruby's. These languages have lots of 'magic programming', few lines of code that do bunch of things. I love them for it, but I know these sort of elegant code can be difficult to catch if you are novice and/or learned to strict C-like programming.