Update not working in SalesForce API

Question

I'm trying to update a record via the SalesForce API (Enterprise WSDL).

The code below executes fine, and the saveResult returned says that the operation was successful.

Yet, when I look in SalesForce - the record has not been updated. The only thing that I can think of is that I am using the wrong Id - But I have quintuple checked this and checked it again and then re-checked it.

Has anybody encountered something like this before? Alternatively, I will be so pleased if someone can point out the stupid mistake that I've probably made somewhere :-)

sforce.Participant__c updateParticipant = new sforce.Participant__c();

        updateParticipant.Id = participant.Id.Length == 15? participant.Id : participant.Id.Substring(0, 15);

        if (updateType == "pre")
        {
            updateParticipant.Manual_Download_Date__c = DateTime.Now;
            updateParticipant.Manual_Download__c = true;
        }
        else if (updateType == "post")
        {
            updateParticipant.Post_Class_Manual_Download__c = true;
            updateParticipant.Post_Class_Manual_Downloaded_Date__c = DateTime.Now;
        }

        sforce.SaveResult[] result = SFLib.sfdc.update(new sforce.sObject[] { updateParticipant });
        if (result == null || result.Length <= 0)
            return false;
        else
        {
            if (result[0].success == true)
                return true;
            else
                throw new Exception("Update participant failed", new Exception(result[0].errors[0].message));
        }

Answer 1

When using .Net to call the Update method on the API, you need to set the *fieldname__cSpecified* field explicitly. E.g.

updateParticipant.aDateField_StartDate__c = DateTime.Now;
updateParticipant.aDateField_StartDate__cSpecified = true;