Can I use a picklist/lookup as my primary attribute?

In my experience it's safe to say that CRM's approach of always needing the primary attribute of a custom entity to be an nvarchar attribute  unfortunately doesn't fit all business scenarios.

Take the example where an organisation has a complex product management scenario where the standard product functionality has to be suppressed and replaced with something more suitable. Within the Account record you may want to see all of the products owned by the organisation. If you have a standard catalogue of products, having to name each one whenever a customer acquires said product is far from ideal.

There are a couple of ways of dealing with this, but I generally like to use JavaScript to plug the 'gap'.

So say we want to have a picklist of 'Product' for our primary attribute on our new product entity, we could do the following:

1. Create the new entity, schema name of new_product.
2. In the new entity, give the primary attribute a name of new_productname (Name this 'Product Name').
3. Create a new pick-list attribute called new_productnamepicklist (Also name this 'Product Name').
4. Place the picklist attribute front & centre on your entity
5. Place the primary attribute elsewhere and disable it... I generally use a 'System' section on an 'Admin' tab.

Now we just need some JavaScript to automatically populate the new_productname attribute with the value from new_productnamepicklist attribute. Place the following code in the onChange event of the new_productnamepicklist attribute:

var CRM_FORM_TYPE_CREATE = 1;
var CRM_FORM_TYPE_UPDATE = 2;

if ((crmForm.FormType == CRM_FORM_TYPE_CREATE) || (crmForm.FormType == CRM_FORM_TYPE_UPDATE)){
    //get our value from the picklist - make sure you use SelectedValue, not DataValue as we want the text, not the item code.
    var recName = crmForm.all.new_productnamepicklist.SelectedValue;

    //Set the attribute name
    crmForm.all.new_productname.DataValue = recName;
    //Don't forget to force submit as the attribute is disabled on the form.
    crmForm.all.new_productname.ForceSubmit = true;    
}

Please be aware that while this particular approach is very simple to implement, it has its limitations. As the work is being done on the form, the onChange event will not fire if the record is updated as part of a bulk edit, or if it is created via an import or through the web services etc. If you need a more sophisticated solution to handle those scenarios, you will want to use a plugin - I'll try and write a follow-up with more detail on that approach when I get a chance.

Lastly, if you face this challenge, please be sure to give some thought to your views. If you look at a list of products, there are few things less helpful than seeing row after row of a single product. You will need to add extra attributes to your view columns to make it easy for your user to identify the data they need.