Jmeter - Using GET/POST with single call - While loop

Why don't you just change your CSV file to include the HTTP Request method along with all other parameters like:

TC_name, login_id, excpecedCode, method
test_with_valid_login_id,2132537288,200,GET
test_with_valid_login_id,2132537288,200,POST
test_with_unknown_login_id,11111,200,GET
test_with_unknown_login_id,11111,200,POST
test_with_known_login_id,1,200,GET
test_with_known_login_id,1,200,POST
test_with_invalide_login_id,dsddfd,400,GET
test_with_invalide_login_id,dsddfd,400,POST
test_with_negative_login_id,-100,400,GET
test_with_negative_login_id,-100,400,POST

If the CSV file is not something you can control you can

1. Create a simple text file called methods.txt in the "bin" folder of your JMeter installation looking like:

   GET
   POST
   

2. Put the request(s) you want to repeat under the Loop Controller with 2 Loops

3. Use the following __groovy() function instead of ${method} in the HTTP Request sampler:

   ${__groovy(new File('methods.txt').readLines().get(vars.get('__jm__Loop Controller__idx') as int),)}