Multi tenancy System.NullReferenceException: 'TenantId claim not found' tenantClaim was null.

[mvmshakkir]

my code is
public static ClaimsPrincipal CreatePrincipal(IUserRetrieveService userRetriever, string username, string authType, int TenantId)
{
if (userRetriever is null)
throw new ArgumentNullException(nameof(userRetriever));

if (username is null)
    throw new ArgumentNullException(nameof(username));

var user = (UserDefinition)userRetriever.ByUsername(username);
if (user == null)
    throw new ArgumentOutOfRangeException(nameof(username));

if (authType == null)
    throw new ArgumentNullException(nameof(authType));

var identity = new GenericIdentity(username, authType);
identity.AddClaim(new Claim(ClaimTypes.NameIdentifier, user.Id));
identity.AddClaim(new Claim("TenantId", user.TenantId.ToInvariant())); // add tenant // Adding TenantId claim as string

    return new ClaimsPrincipal(identity);

}

using System;
using System.Linq;
using System.Security.Claims;
namespace DailyStandUp
{
public static class ClaimsPrincipalExtensions
{
public static int GetTenantId(this ClaimsPrincipal user)
{
if (user is null)
throw new ArgumentNullException(nameof(user));

        var tenantClaim = user.Claims.FirstOrDefault(x => x.Type == "TenantId");
        if (tenantClaim is null)
            throw new NullReferenceException("TenantId claim not found");

        return int.Parse(tenantClaim.Value);
    }
}

}
here it throwing error System.NullReferenceException: 'TenantId claim not found'

tenantClaim was null.