Handling multiple role from IdentityServer4 on the client

MultipleRole.cs

/*
When IdentityServer4 returns role in access-token JSON the type of the "role" member value differs depending on how many roles are present. Two cases:

1) Single role - the value is a string, e.g. "role": "patient".
2) Multiple roles - the value is an array-of-string, e.g. "role": ["patient", "agent"]

The AspNetCore framework on the client side does not like the second case, and it assumes a string, giving an error saying that it can't cast from Newtonsoft.Json.Linq.JArray to Newtonsoft.Json.Linq.JToken.

You can work around this by checking the type of the role JSON in OpenIdConnectOptions.
*/

o.Events.OnUserInformationReceived = context =>
{
    if (context.User.TryGetValue(JwtClaimTypes.Role, out var role))
    {
        var roleNames = role.Type == JTokenType.Array 
            ? role.Select(x => (string)x) 
            : new[] { (string)role };
        var claims = roleNames.Select(rn => new Claim(JwtClaimTypes.Role, rn));
        var id = context.Principal.Identity as ClaimsIdentity;
        id?.AddClaims(claims);
    }
    return Task.CompletedTask;
};

/*
This replaces any existing role-claim configuration, e.g.

o.ClaimActions.Add(new JsonKeyClaimAction(JwtClaimTypes.Role, JwtClaimTypes.Role, JwtClaimTypes.Role));
*/