Earlier this year I worked on a workflow project that required the fields of a list item be hidden based on the status of the record and the users application rights. After some digging around I found the ListFieldIterator class (see http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.webcontrols.listfielditerator_methods.aspx) which has a IsFieldExcluded method (see http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.webcontrols.listfielditerator.isfieldexcluded.aspx).  This allows you to exclude fields from being displayed when iterating over the fields in a list item.

The next problem was how to create my own field iterator  and use it with my content type. This led me to Custom Form Templates: Form Templates are the method by which SharePoint displays a content type in display, new, and edit form. By default lists all use the same template. The template is a combination of HTML markup and server control references; some of the controls are standard ASP.Net control and some are SharePoint TemplateBasedcControl controls (see http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.webcontrols.templatebasedcontrol.aspx). The TemplateBasedControls can take a template which is a combination of HTML markup, ASP.Net server controls and SharePoint TemplateBasedControl controls - and so it repeats. This is the way in which SharePoint builds the UI. You can find the templates, all of which have a name, in the 12\Template\ControlTemplates directory; most of them in one file - defaulttemplates.ascx.

Searching through this file you can find template for laying out such things as document items, standard toolbars, view selectors etc. You can modify the default behavior for a given template by creating a new template with the same name and deploying it to the 12 hive and restarting IIS. You should never modify the installed files in the 12 hive as the files are used by all sites on the farm and you could break functionality.

By creating custom form layouts it is possible to layout list items in any way you need, for example the SharePoint KPI edit pages are just custom layout forms. You can change the markup and control order in the template, additionally  you can define alternate templates for use with a particular control - this separation of UI markup from the control code is very powerful and flexible.

Attaching a Form template to a content type

For our application we were defining new content types using CAML and a feature definition. Attaching the custom form is achieved by adding some additional CAML markup to the type declaration:

<Elements  xmlns="http://schemas.microsoft.com/sharepoint/" >
    <ContentType Description="Licensing Task Content Type"
                 ID="0x01008F4414E2376E47d2A84745642AFA85E3"
                 Name="LicensingTask"
                 Group="Syrinx"
                 Version="0">

...
        <XmlDocuments>
            <XmlDocument NamespaceURI="http://schemas.microsoft.com/sharepoint/v3/contenttype/forms">
                <FormTemplates xmlns="http://schemas.microsoft.com/sharepoint/v3/contenttype/forms">
                    <Display>LicenseDisplayForm</Display>
                    <Edit>LicenseEditForm</Edit>
                    <New>LicenseEditForm</New>
                </FormTemplates>
            </XmlDocument>

In the above example the LicensingTask content type uses a form called LicenseEditForm for new and edit and LicenseDisplay form for displaying items.

The content of the template is :

   1:  <SharePoint:RenderingTemplate ID="LTCLicenseEditForm" runat="server">

   2:      <Template>

   3:          <wssuc:ToolBar CssClass="ms-formtoolbar" id="toolBarTbltop" RightButtonSeparator="&nbsp;" runat="server">

   4:              <template_rightbuttons>

   5:                  <SharePoint:SaveButton runat="server"/>

   6:                  <SharePoint:GoBackButton runat="server"/>

   7:              </template_rightbuttons>

   8:          </wssuc:ToolBar>

   9:          <table class="ms-formtable" style="margin-top: 8px;" border="0" cellpadding="0" id="formTbl"

  10:              cellspacing="0" width="100%">

  11:              <ltc:TaskListFieldIterator runat="server" />

  12:          </table>

  13:          <SharePoint:CreatedModifiedInfo ID="CreatedModifiedInfo1" runat="server" />

  14:          <wssuc:ToolBar CssClass="ms-formtoolbar" id="toolBarTblbottom" RightButtonSeparator="&nbsp;"

  15:              runat="server">

  16:              <template_rightbuttons>

  17:                  <SharePoint:SaveButton runat="server"/>

  18:                  <SharePoint:GoBackButton runat="server"/>

  19:              </template_rightbuttons>

  20:          </wssuc:ToolBar>

  21:      </Template>

  22:  </SharePoint:RenderingTemplate>

  23:   

Line 11 is where the use of the custom field iterator is defined. The prefix ltc is used to identify the control to be used is from a specific assembly and namespace, at the top of the template ascx file there is a prefix definition:

<%@ Register TagPrefix="ltc" Assembly="Licensing, Version=1.0.0.0, Culture=neutral, PublicKeyToken=6c1fd21dbc7fb55e"
    Namespace="syrinx.SharePoint.Licensing.WebControls" %>

For more information on layout forms see http://msdn.microsoft.com/en-us/library/aa544142.aspx 

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