Exact match formula for Multiple select field when value has comma

[Samvel_Siradegh]

I need a formula to check if there is exact matching for multiple select field when values can have comma. Here is a sample multiple select I can have:

• a
• b
• c
• a,b

I need to check if users selection is exactly 'c' and 'a,b'. All solutions I found (like using FIND) are not working with comma.

[Sho]

How about this formula.

IF(
  AND(
    FIND("a,b",{select}),
    FIND("c",{select}),
    LEN({select})=LEN('"a,b", c')
  )
  ,1
)

also this formula

IF(
  OR(
    '"a,b", c'={select},
    'c, "a,b"'={select}
  )
  ,1
)

Hmmm, Is there any better way?

[Samvel_Siradegh]

Thanks for response @Sho , but this will not work, as in my case 2 of 4 items can be selected (or 1, or 3, or all 4) and 

LEN({select})=LEN('"a,b", c')

will not be true, as for this sample {select} is 'a,b,c,"a,b"'

[Sho]

Did you try it?

"LEN()" part checks to see if any other options have been selected.

In the case of 'a,b,c, "a,b"'

IF(
  AND(
    FIND("a",{select}),
    FIND("b",{select}),
    FIND("c",{select}),
    FIND("a,b",{select}),
    LEN({select})=LEN('a, b, c, "a,b"')
  )
  ,1
)

[Samvel_Siradegh]

Of course I tried it.
Let me explain more visual way.
This is my multiple select:

You can see there are 4 options.
This is selection I want to check:

Hope this is more accurate description.

[Sho · Accepted solution]

Ah, I see why the FIND function is not working.
Multi-select is difficult to process because it's just text.

How about this formula?

IF(
  AND(
    REGEX_MATCH("##"&REGEX_REPLACE({select},", ","##")&"##","##c##"),
    REGEX_MATCH("##"&REGEX_REPLACE({select},", ","##")&"##",'##"a,b"##'),
    LEN({select})=LEN('c, "a,b"')
  )
  ,1
)

[Samvel_Siradegh]

I removed LEN and looks like it works, will try some corner cases and will update here.
Here is formula I am trying

IF(
  AND(
    REGEX_MATCH("##"&REGEX_REPLACE({select},", ","##")&"##","##c##"),
    REGEX_MATCH("##"&REGEX_REPLACE({select},", ","##")&"##",'##"a,b"##')
  )
  ,1
)

[Sho]

If you remove the LEN, it will contain "c" and "a,b" and will match any other choice.
OK if not a problem!

[Samvel_Siradegh]

@Sho you are right, this is not exact matching. Your version was correct, I just had typo on my side. Will do some more tests and will accept as solution.