I'm working on a new project and in the last few weeks I learned some new things that I want to share with you. Now most things aren't new for blogging so I'm not going to write the how-to's but just mentioning some very useful articles that helped me along the way.

• Support and the 'hmm.. that's handy!'-things
• Building Custom Field Controls

Support and the 'hmm.. that's handy!'-things

• Do you 0x81070201?, post by Carloshm (MS IW Consultant from Spain). When you forgot to add the related files of your feature, the schema of the list definition, that should be placed in the solution schema (manifest.xml) you get that error while you attempt to create the list.
• Make sure if you are using U2U's CAML Query Builder that you use the latest version of the tool. Otherwise you will get the following error if you open up a list (using the tool) "field type <customfieldname>is not installed properly".
• If you get the same error in SharePoint itself then take a look at the following post :
• Sjoert Ebben - Sharepoint blog- field type field is not
• Looking for all the internal field names of the SharePoint columns? Like "LinkTitle, Edit, Created_x0020_By" there is a class called SPBuiltInFieldId which has all the FieldID's in them.

• Remember back in 2003 days when you wanted to get and set the value of a hyperlink column and you had to make sure that the string looked exactly like this "htp://portal, This is the portal" ? Well luckily for each 'exotic' SharePoint fieldtype/column there is a class. For the hyperlink field there is the "SPFieldUrlValue" class. Which has two properties which are "Description" and "URL".

SPFieldUrlValue url = new SPFieldUrlValue();
url.Description = contextWeb.Title;
url.Url = contextWeb.Url;
item["Url"] = url;

And to give another example, if you are using the Person/Group column there is the following class you can use : "SPFieldUserValue". Now if you have enabled the 'allow multiple users or groups' you have the following class to get those users and or groups : "SPFieldUserValueCollection"

SPFieldUserValueCollection Users = new SPFieldUserValueCollection(item.ParentList.ParentWeb, item["Users"].ToString());
foreach (SPFieldUserValue User in Users)
{
       string username = User.User.Name;
       string email = User.User.Email;                    
}                

• To use strings for identifying (custom) contenttypes is not very elegant. Therefore you can use the SPContentTypeID struct like this:

private SPContentTypeId CustomlTask = new SPContentTypeId("0x010022B9BB64405F4ab4A595E68AB308359B00fdba34def6d7466987f46892ec7fe880");

Building Custom Field Controls

• Jim Yang's Create custom field type in WSS V3 post
• Nick's Create custom field types for SharePoint  post
• U2U's article about Microsoft SharePoint 2007 custom field type for Microsoft CRM Dynamics 4.0