Powershell if condition to validate if a String with special charcs is NULL or EMPTY

Question

I have a github secret which has value like below

Azuresecret is  <publishData><publishProfile profileName="a00008dfdgdfhfg" - Web Deploy" publishMethod="MSDeploy" publishUrl="a00008w543tgddg" <databases /></publishProfile></publishData>

Now i am trying to validate if the secret is empty or Null using powershell However i get Many error messages like this

  ... g]::IsNullOrEmpty("<publishData><publishProfile profileName="a00008-a ...
   +                                                                  ~
   Missing ')' in method call.

 Missing closing ')' in expression.
      At E:\_temp\0007a890-9ecb-4cce-b1e.ps1:10 char:90
    + ... a><publishProfile profileName="a00008-accountsfunctionapp-dev - Web D ...
      +                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Missing closing ')' after expression in 'if' statement.

Any help will be highly appreciated