I am trying to make a registration form so people can register on my website. However, everytime I actually try to save the new member, the application blows up in my face.

if (Membership.GetUserNameByEmail(txtEmail.Text) == null)
{
 //create a member
 MembershipUser newUser = Membership.CreateUser(txtUserName.Text.ToString(), txtPassWord.Text.ToString(), txtEmail.Text.ToString());
   Roles.AddUserToRole(txtUserName.Text, "websiteMember");
}

That is the code I am trying to use. I want to check if there already is a member using the given email address and if there isn't, I want to create a new member using the data supplied by the user. The "== null" part is probably wrong, but I tried a dozen of different things already and nothing works.

Stack trace error:

[NullReferenceException: Object reference not set to an instance of an object.]
   umbraco.cms.businesslogic.Content.CreateContent(ContentType ct) +188
   umbraco.cms.businesslogic.member.Member.MakeNew(String Name, String Email, MemberType mbt, User u) +601
   umbraco.providers.members.UmbracoMembershipProvider.CreateUser(String username, String password, String email, String passwordQuestion, String passwordAnswer, Boolean isApproved, Object providerUserKey, MembershipCreateStatus& status) +197
   System.Web.Security.Membership.CreateUser(String username, String password, String email, String passwordQuestion, String passwordAnswer, Boolean isApproved, Object providerUserKey, MembershipCreateStatus& status) +207
   System.Web.Security.Membership.CreateUser(String username, String password, String email) +30
   memberControls.memberControls.memberSignUp.btnSubmit_Click(Object sender, EventArgs e) +259
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +118
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +112
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5563

I am using Umbraco 4.5.1 and after some searching, I still have been unable to find an answer, maybe I missed it, but if I could be pointed in the right direction that would be great.

-Ferdy