How to kill the test left UI object in C#?

Hi,

Could you please clarify what do you mean?

If you are wondering about the lifetime of the variables in your C# test code, it is following regular rules for .Net.

If you are wondering about UI objects of the tested application, then the flow is like this:

-- Tested application creates its UI objects as it is implemented by developers;

-- TestLeft's runtime engine monitors these objects and maintains its internal objects tree;

-- When your test code searches for an UI object, the reference to the object from the above objects tree is returned;

-- When the tested application destroys the referenced UI object, TestLeft's runtime engine invalidates it in the objects tree and this is (automatically) reflected in your test code.

https://support.smartbear.com/testleft/docs/using/creating-tests/searching-for-objects.html and https://support.smartbear.com/testleft/docs/using/creating-tests/object-identification/understanding-object-identification.html might help further.