test.cs

private void textControl1_SubTextPartEntered(object sender, SubTextPartEventArgs e)
{
    UserInfo userInfo;

    // deserialize the JSON string to a UserInfo object if data is available
    if (e.SubTextPart.Data != null)
    {
        userInfo = JsonSerializer.Deserialize<UserInfo>(e.SubTextPart.Data);

        MessageBox.Show(userInfo.Name);
    }
}