title: Error collection is modified, cannot perform enumeration on sharepoint list
body: <p>not sure why i get the above error, i know its because of UpdateWorkflowAssociation is inside the foreach but i need it that way 
  A simple help will be highly appreciated </p>
  
  <pre><code>                        `siteName = "http://xyz";
  
                          newCleanupDays = 5;
                          assoCounter = 0;
                          using (wfSite = new SPSite(siteName))
                          {
                              using (wfWeb = wfSite.OpenWeb())
                              {
  
                                 //wfList = wfWeb.Lists[libraryName];
                                  SPListCollection collList = wfWeb.Lists; //Open Lists
                                  SPWorkflowAssociation _wfAssociation = null;
  
                                  foreach (SPList oList in collList)
                                  {
                                      if (oList.WorkflowAssociations.Count &gt; 0)
                                      {
                                          foreach (SPWorkflowAssociation a in oList.WorkflowAssociations)
                                          {
                                              if (a.Name != null || a.Name != string.Empty)
                                              {
                                                  a.AutoCleanupDays = newCleanupDays;
                                                  _wfAssociation = a;
                                                  assoCounter++;
                                              }
                                              else
                                              {
                                                  _wfAssociation = a;
                                              }
  
                                          }
                                          oList.UpdateWorkflowAssociation(_wfAssociation);
                                      }
  
                                  }
                                  System.Console.WriteLine("\n" + wfAssoName + ": " + assoCounter.ToString() + " workflow association(s) changed successfuly!\n");
                              }
                          }`
  </code></pre>