Hello,

I have a community portal where we want to let our customer Self-register. The controller which does this doesn't check if a contact with the same email exists in salesforce before creating the contact/user record. So, we new duplicate contacts area created.

/**
 * An apex page controller that supports self registration of users in communities that allow self registration
 */
public class CommunitiesSelfRegController {

    public String firstName {get; set;}
    public String lastName {get; set;}
    public String email {get; set;}
    public String password {get; set {password = value == null ? value : value.trim(); } }
    public String confirmPassword {get; set { confirmPassword = value == null ? value : value.trim(); } }
    public String communityNickname {get; set { communityNickname = value == null ? value : value.trim(); } }
    
    public CommunitiesSelfRegController() {
        String expid = ApexPages.currentPage().getParameters().get('expid');            
        if (expId != null) {
            Site.setExperienceId(expId); 
        }    
    }
    
    private boolean isValidPassword() {
        return password == confirmPassword;
    }

    public PageReference registerUser() {
    
           // it's okay if password is null - we'll send the user a random password in that case
        if (!isValidPassword()) {
            ApexPages.Message msg = new ApexPages.Message(ApexPages.Severity.ERROR, Label.site.passwords_dont_match);
            ApexPages.addMessage(msg);
            return null;
        }    

        String profileId = null; // To be filled in by customer.
        String roleEnum = null; // To be filled in by customer.
        String accountId = ''; // To be filled in by customer.
        
        String userName = email;

        User u = new User();
        u.Username = userName;
        u.Email = email;
        u.FirstName = firstName;
        u.LastName = lastName;
        u.CommunityNickname = communityNickname;
    u.ProfileId = profileId;
    
        String userId;

        try {
            userId = Site.createExternalUser(u, accountId, password);
        } catch(Site.ExternalUserCreateException ex) {
            List<String> errors = ex.getDisplayMessages();
            for (String error : errors)  {
                ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, error));
            }
            
            // This message is used for debugging. Do not display this in the UI to the end user.
            // It has the information around why the user creation failed.
            System.debug(ex.getMessage());
        }
        
        if (userId != null) { 
            if (password != null && password.length() > 1) {
                return Site.login(userName, password, ApexPages.currentPage().getParameters().get('startURL'));
            }
            else {
                PageReference page = System.Page.CommunitiesSelfRegConfirm;
                page.setRedirect(true);
                return page;
            }
        }
        return null;
    }
}

How can I modify this apex class to make sure that first it checks if the email given on the registration page exists and if exists use that contact to create the community user. If not, create a new contact (what it does now).

Thank you very much in advance for your help.