Sending a Email Template from APEX

Question

I'm attempting send a Text email from Apex code, Email is sending without body.

I have created a new LWC button and Placed in custom Object Detailed page. On Clicking of the button this Apex method will be called and Send email to the User.( Email address are stored in Same Custom Object).

I'm successfully receiving the email, subject is coming across as I expect, but the body has some dynamic value.(Now the body coming as plain text)

public static void sendEnrollmentForm(Id EnrollmentId){

    //Get Email Address
    Enrollment__c Enrollment = [select  Id, Family_Email__c from Enrollment__c WHERE Id=:EnrollmentId]; 

    // get an email template
    EmailTemplate tpl = (EmailTemplate)[select Id, Subject, Body FROM EmailTemplate 
                                        WHERE Name = 'Enroll Email' limit 1];

    Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
    String[] toAddresses = new String[] {Enrollment.Family_Email__c};


    mail.setTemplateId(tpl.Id);
    mail.setToAddresses(toAddresses);
    mail.setReplyTo('support@safarikid.com');
    mail.setSenderDisplayName('Safari Kid');
    mail.setSubject(tpl.Subject);
    mail.setPlainTextBody(tpl.Body);
    mail.setBccSender(false);
    mail.setSaveAsActivity(false);
    mail.setUseSignature(false);

    //send the email
    List<Messaging.SendEmailResult> results = Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });

    // we can then check for success
    if (results[0].success) {
        System.debug('The email was sent successfully.');
    } else {
        System.debug('The email failed to send:  ' +  results[0].errors[0].message);
    }
}

Answer 1

First you didnt query body field from EmailTemplate object. Second you are not setting setHtmlBody or setPlainTextBody in your code either.

e.g.

Query

EmailTemplate tpl = (EmailTemplate)[SELECT Id, Subject, Body FROM EmailTemplate WHERE Name = 'Enroll Email' LIMIT 1];

Setting the body

mail.setPlainTextBody = 'This is test email message.'; Or

mail.setPlainTextBody = tpl.Body;

Answer 2

You should populate WhatId when you use EmailTemplate in order to merge fields :

message.setWhatId(account.Id);

Here is link for example : example