How to pass queryParams to API post request using Angular 8

Hi, I have a API call to the server in the below format


I am trying to make API call like below.

return< any >
(this.url + classId + ‘/message’, body, {params: -----------})

But I’m not getting to pass the params value like above format (userIds=userId,rollNo&userIds=userId,rollNo&userIds=userId,rollNo). How can i achieve this?

Thank You.