gistfile1.txt

public XeroClient GetClient()
{
    var xeroConfig = new XeroConfiguration()
    {
        ClientId = _xeroConfig.Value.XeroConnect.ClientId,
        CallbackUri = new Uri(_xeroConfig.Value.XeroConnect.RedirectUri),
        Scope =
            "openid profile email offline_access files accounting.transactions accounting.contacts accounting.settings",
        State = "WinFormsApp"
    };
    return new XeroClient(xeroConfig);
}
private async Task<string> Refresh()
{
    var xeroClient = GetClient();
    var token = _xeroTokenStore.Find(p => p.TenantId == _xeroConfig.Value.XeroConnect.TenantId)
        .FirstOrDefault();
    token = await xeroClient.RefreshAccessTokenAsync(token) as DbXeroToken;
    _xeroTokenStore.Upsert(new DbXeroToken(_xeroConfig.Value.XeroConnect.TenantId, token));
    return token?.AccessToken;
}