Adding a field to claim for Azure AD in ASP.NET Core 6 - asp.net-core

Question

My MVC web application previously used cookie based authentication handled by identity framework and usernames and passwords stored in my db. However, I have since moved to Azure AD for authentication and it is working great however I use a field in my database for each user called InternalUserNumber and this is used in many stored procedures and table valued functions called from my web application's dapper queries. So on authenticating to Azure AD the user is redirected to the homepage which on load I was planning to run a sql query using the preferred_username (email address) against our database to get the UserID and I was going to store it as a session variable which I can use later in my code. However, this got me thinking I use to store the UserID as a claim in the cookie as follows:
new Claim(ClaimTypes.Name, user.InternalUserNumber.ToString())
Is this still doable using the Azure AD cookie which is generated after logging in? I do not have access to the admin panel in Azure AD so this has to be all code based. Or is my only option storing this in the session as a variable and if so whats the best route for that? I would note i do plan to implement SignalR which I read you cannot use session if you are going to use SignalR so theres that potential issue for that route.
Thanks
Edit :
I have actually added some code which uses an event passed in program.cs. I was trying to implement a service to do the following code but I failed to be able to figure it out but instead put directly inside the event code as shown below. My issue is I cannot access the preferred_username in HttpContext object as it returns null? I am able to use HttpContext in my controllers so why am I not able to use it here in Program.CS during this event being triggered?
builder.Services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
.AddMicrosoftIdentityWebApp(options =>
{
builder.Configuration.Bind("AzureAd", options);
options.Events = new OpenIdConnectEvents
{
OnTokenValidated = context =>
{
//var service = context.HttpContext.RequestServices.GetRequiredService<ISomeService>();
//var result = await service.DoSomethingAsync();
string query = "select dbo.A2F_0013_ReturnUserIDForEmail(#Email) as UserID";
string connectionString = builder.Configuration.GetValue<string>("ConnectionStrings:DBContext");
string signInEmailAddress = context.HttpContext.User.FindFirstValue("preferred_username");
using (var connection = new SqlConnection(connectionString))
{
var queryResult = connection.QueryFirst(query, new { Email = signInEmailAddress });
// add claims
var claims = new List<Claim>
{
new Claim("UserID", queryResult.UserID.ToString())
};
var appIdentity = new ClaimsIdentity(claims);
context.Principal.AddIdentity(appIdentity);
}
return Task.CompletedTask;
},
};
})
.EnableTokenAcquisitionToCallDownstreamApi(initialScopes)
.AddMicrosoftGraph(builder.Configuration.GetSection("DownstreamApi"))
.AddInMemoryTokenCaches();