Duplicate user insertion on membership user created event

i use below event on login control created event to add user to sepecific role.
Code
 protected void CreateUserWizard1_CreatedUser(object sender, EventArgs e)     {         string userName = CreateUserWizard1.UserName;         Roles.AddUserToRole(userName, "User");     }

web config:
    <membership defaultProvider="CustomizedProvider">             <providers>                 <add name="CustomizedProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="DBConnection" applicationName="ats"  maxInvalidPasswordAttempts="20" minRequiredNonalphanumeric ...