I am getting a DML not allowed error from my visual force page.

The error is caused by an update and insert call in a method which seems to be the constructor.

Can someone give me a solution to how I can update and insert this list of records without hitting this error?

Code snippet:

public with sharing class SalesInvoiceHelper
public static List<CTransaction_Item__c> generateSalesInvoiceLineItems(Id salesInvoiceId, List<OpportunityLineItem> prodList)
    List<CTransaction_Item__c> lineItems = new List<CTransaction_Item__c>();
    List<OpportunityLineItem> oneOffPayments = new List<OpportunityLineItem>();
    List<OpportunityLineItem> renewals = new List<OpportunityLineItem>();
    RenewalValues__c rv = RenewalValues__c.getOrgDefaults();

    for(OpportunityLineItem oli : prodList)
      //I removed the code in here from the snippet to keep my post from being too long, as it is quite long and not causing any problems.           

    **//This line is causing DML not allowed.**
    if(oneOffPayments.size() > 0)  {update oneOffPayments; oneOffPayments.clear();} 

    **//This line is causing DML not allowed.**
    if(renewals.size() > 0){ insert renewals; renewals.clear();}

    return lineItems; //Returns all of the items

1 Answer 1


You can perform a DML operation in an action method. apex:page's action method will be called after constructors but before the page renders:

<apex:page controller="SalesInvoiceHelper" action="{!generateLineItems}" ...>


<apex:page controller="Sales_Invoice__c" extensions="SalesInvoiceHelper" action="{!generateLineItems}" ...>
  • Hi, thanks for the reply. But my controller is not the SalesInvoiceHelper. The class is called later on in the code, but when I remove the update and insert lines, the page no longer throws the DML not allowed error. Feb 5, 2019 at 15:50
  • 1
    @AlexanderAtkinsoon Whatever class is the controller would need to have the method to be called. The point of my answer is that you simply need to call an action method.
    – sfdcfox
    Feb 5, 2019 at 15:51
  • The documentation discourages performing DML in the method specified by the action parameter of <apex:page>, but...eh. I just take that as a friendly suggestion. I suppose the behavior might not be well defined if, for example, you end up running into an uncatchable exception in executing the action method. Any input from you sfdcfox?
    – Derek F
    Feb 5, 2019 at 16:05
  • 2
    @DerekF The recommendation is based on the fact that it opens the possibility of CSRF-style attacks. Imagine someone embeds an image or iframe in an email with a URL to this page, and the user is already authenticated, it could result in unintended actions performed by the user. There's a very good reason why it should be avoided if possible. As far as undefined behavior, the action method on apex:page is the same as any other, uncaught exceptions result in the B+W VF error page.
    – sfdcfox
    Feb 5, 2019 at 16:11

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