Create on behalf of token using managed identity

Hello,

I am trying to create an on behalf of token for one of the applications i am building.

I have been following microsoft doc,

and this is the code I see for creating confidential client applications. However, we do not use client secret for any of our entra apps. I wanted to know is there a work around for app services that use managed identity to create on behalf of tokens.

     _app = ConfidentialClientApplicationBuilder.Create(clientId)
            .WithClientSecret(clientSecret)
            .WithAuthority(new Uri($"https://login.microsoftonline.com/{tenantId}"))
            .Build();