My company has an internal application where I need to pull/display pictures of all the employees from office 365 with out user intervention.
From what I read online I think I need to call Microsoft graph getphoto API in daemon application to achieve this as per this link (https://developer.microsoft.com/en-us/graph/docs/authorization/app_only).
Will this be a right approach? If yes please point me to any C# sample codes related to this.
Appreciate your responses.
Yes, this is exactly the type of application you will want to build. App-only (machine-to-machine) authentication should be used anytime you don't need a user present to execute functionality.
You can take a look at the ASP.NET Core App Only sample to get a sense of how to register and set up your app to use app-only authentication. The sample goes on to use this access token to set up webhooks, but you can replace this logic with your custom code. You will want to select the scope User.ReadBasic.All to have access to users' profile photos.