formAMPscriptMultiSelectPicklist.html

<script runat="server">
  Platform.Load("Core","1.1.1");
  try{
</script>
%%[
IF RequestParameter("submitted") == true THEN

 SET @preferences = CONCAT(
      Iif(RequestParameter("newsletters") == "on", "Newsletters;", ""),
      Iif(RequestParameter("events") == "on", "Events;", ""),
      Iif(RequestParameter("offers") == "on", "Special Offers;", ""),
      Iif(RequestParameter("surveys") == "on", "Surveys;", ""),
      Iif(RequestParameter("promotions") == "on", "Promotions", ""),
    )  

 if not Empty(@preferences) then
  SET @updateRecord = UpdateSingleSalesforceObject(
      "Contact", RequestParameter("subkey"),
      "FirstName", RequestParameter("firstname"),
      "LastName", RequestParameter("lastname"),
      "Email", RequestParameter("email"),
      "Preferences__c", @preferences)
  else
    SET @updateRecord = UpdateSingleSalesforceObject(
      "Contact", RequestParameter("subkey"),
      "FirstName", RequestParameter("firstname"),
      "LastName", RequestParameter("lastname"),
      "Email", RequestParameter("email"),
      "fieldsToNull", "Preferences__c")

  endif 
]%%

Your preferences have been updated.

%%[ELSE 
set @subscriberKey = AttributeValue(_subscriberKey)
set @subscriberRows = RetrieveSalesforceObjects(
   "Contact",
   "FirstName,LastName,Email,Preferences__c",
   "Id", "=", @subscriberKey)

if RowCount(@subscriberRows) == 1 then
  var @subscriberRow, @firstName, @lastName, @email
  set @subscriberRow = Row(@subscriberRows, 1)
  set @firstName = Field(@subscriberRow, "FirstName")
  set @lastName = Field(@subscriberRow, "LastName")
  set @email = Field(@subscriberRow, "Email")
  set @Preferences__c = Field(@subscriberRow, "Preferences__c")
  
IF NOT EMPTY(@Preferences__c) THEN
    SET @rs = BuildRowsetFromString(@Preferences__c,';')
    
    IF rowcount(@rs) > 0 THEN
    
     FOR @i=1 TO rowcount(@rs) DO
      SET @val = Field(Row(@rs,@i),1)
      IF @val == "Surveys" THEN
      SET @Surveys = "checked"
      ELSEIF @val == "Events" THEN
      SET @Events = "checked"
      ELSEIF @val == "Newsletters" THEN
      SET @Newsletters = "checked"
      ELSEIF @val == "Promotions" THEN
      SET @Promotions = "checked"
      ELSEIF @val == "Special Offers" THEN       
      SET @Offers = "checked"
      ENDIF
     NEXT @i
   
    ELSE
    
    SET @Newsletters = ""
    SET @Events = ""
    SET @Offers = ""
    SET @Survays = ""
    SET @Promotions = ""
    
    ENDIF
ENDIF

endif

]%%


      <h2>Please fill in the form:</h2>
      <form action="%%=RequestParameter('PAGEURL')=%%" method="post">
         <label>First name: </label><input type="text" name="firstname" required="" value="%%=v(@firstName)=%%"><br>
         <label>Last name: </label><input type="text" name="lastname" required="" value="%%=v(@lastName)=%%"><br>
         <label>Email: </label><input type="text" name="email" required="" value="%%=v(@email)=%%"><br><br>
        Pref: %%=v(@Preferences__c)=%%<br><br>
        <h2>Update your subscriptions:</h2>
      <input name="newsletters" type="checkbox" %%=v(@Newsletters)=%%><label>Newsletters</label><br>
      <input name="events" type="checkbox" %%=v(@Events)=%%><label>Events</label><br>
      <input name="offers" type="checkbox" %%=v(@Offers)=%%><label>Special Offers</label><br>
      <input name="surveys" type="checkbox" %%=v(@Surveys)=%%><label>Surveys</label><br>
      <input name="promotions" type="checkbox" %%=v(@Promotions)=%%><label>Promotions</label><br>
        <input name="subkey" type="hidden" value="%%=v(@subscriberKey)=%%"><br>
         <input name="submitted" type="hidden" value="true"><br>
         <input type="submit" value="Submit">
      </form>  


%%[ ENDIF ]%%
<script runat="server">
  }catch(e){
    Write(Stringify(e));
  }
</script>