Why am I getting duplicate ApexMessages when concatenating string in a try/catch

Question

I have two different approaches for adding an error to my visualforce page. The first approach I am concatenating a string at the end of exception. The second approach I am simply returning the message from the Exception itself.

However I'm not sure why the first one would display a duplicate and redudant error message. I want to use the first approach (with the record name at the end)... but I don't want the duplicate message in the beginning.

public PageReference saveChanges(){

    problematicIds = new Set<Id>();

    try{
        update InterBUoppz;
    }

    catch(DmlException de) {
    Integer numErrors = de.getNumDml();
    for(Integer i=0;i<numErrors;i++) {
        //Image 1: this gives a duplicate message on top (only for the first error)
        //ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, de.getDmlMessage(i)+' - Opportunity: '+oppListMap.get(de.getDmlId(i)).Name));

        //Image 2: this works fine but it is not as precise
        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, de.getDmlMessage(i)));
    }
    errorsFound = true;
    }

    return null;

}

Image 1 Image 2

Answer 1

The first message is provided to you "for free" when you try-catch a DMLException. Further, the reason why you only see one error in the second example is because duplicate messages are collapsed into a single instance. Therefore, even though you added it manually, there was no need to do so, because it was already added for you. If you don't want the first message to appear, you'll want to use the Database methods and not cause an exception.

---

problematicIds = new Set<Id>();
Database.SaveResult[] results = Database.update(InterBUoppz, false);
Integer numErrors = 0;
for(Database.SaveResult result: results) {
    if(!result.isSuccess()) {
        numErrors++;
        // Display your custom error message with ApexPages.addMessage...
    }
}

Answer 2

Couldn't you just add create a string and add your message to it? I may not understand the question well enough though

Integer numErrors = de.getNumDml();
Boolean errorsFound = false;
String errorMessage = '';

for(Integer i=0; i < numErrors; i++) 
{
    errorMessage +=   de.getDmlMessage(i) + '<br />  ';
    errorsFound = true;
}

if(errorsFound)
{
   ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR, errorMessage));
}