Integrate Graph API in Existing Asp.net Mvc 5 Application

I have Asp.net MVC 5 application which is live.Now there is an need of integrating Microsoft Graph API to get/post Contact record from/to Office 365.
As i am using my Custom Authentication and authorization in my application,Now how can i excape Graph API Authentication (OWIN) extra stuff to work with Graph API.

Every time i login to my application,and calling Graph API endpoint ,popups open and i enter hotmail credentials . I am using this example : https://docs.microsoft.com/en-us/learn/modules/msgraph-build-aspnetmvc-apps/

it give me error.

IDX21323: RequireNonce is '[PII is hidden]'. OpenIdConnectProtocolValidationContext.Nonce was null, OpenIdConnectProtocol.ValidatedIdToken.Payload.Nonce was not null. The nonce cannot be validated. If you don't need to check the nonce, set OpenIdConnectProtocolValidator.RequireNonce to 'false'. Note if a 'nonce' is found it will be evaluated.