Sharepoint Development

in order to get an additional field you need to edit the

C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\TEMPLATE\XML\FLDTYPES.XML

the file lookes like this



   
   
        Related Categories Field
        Note
        Related Categories Field
        My Description
        TRUE
        TRUE
        TRUE
        TRUE
        TRUE
       
           blabla.SharePoint.CustomFields.RelatedCategoriesField, RealCommerce.SharePoint.CustomFields, Version=1.0.0.0, Culture=neutral, PublicKeyToken=109625d57bdfbe68
       
   


this section :


           blabla.SharePoint.CustomFields.RelatedCategoriesField, RealCommerce.SharePoint.CustomFields, Version=1.0.0.0, Culture=neutral, PublicKeyToken=109625d57bdfbe68
       
refers to the FieldClass that you need to build in this manner:

namespace Blabla.SharePoint.CustomFields
{
    ///

    ///

    public class RelatedCategoriesField : SPFieldMultiLineText
    {
        public RelatedCategoriesField(SPFieldCollection fields, string fieldName)
            : base(fields, fieldName)
        { }

        public RelatedCategoriesField(SPFieldCollection fields,
                           string typeName,
                           string displayName)
            : base(fields, typeName, displayName)
        { }

        public override BaseFieldControl FieldRenderingControl
        {
            get
            {
                BaseFieldControl fldControl = new RelatedCategoriesFieldControl();
                fldControl.FieldName = InternalName;
                return fldControl;
            }
        }
    }

}

and the FieldControl:


namespace BlaBla.SharePoint.CustomFields
{
    public class RelatedCategoriesFieldControl : AjaxBaseFieldControl
    {

        #region Members

        protected RelatedCategoriesUC m_RelatedCategoriesUC;
        protected ResourceMgr m_Resource;

        #endregion

        #region Properties

        public ResourceMgr oResource
        {
            get
            {
                if (m_Resource == null)
                {
                    m_Resource = new ResourceMgr(ResourceMgr.ResourceFiles.CmsResources);
                }
                return m_Resource;
            }
        }

        public override object Value
        {
            get
            {
                return m_RelatedCategoriesUC.Value;
            }
            set
            {
                m_RelatedCategoriesUC.Value = value;
            }

        }

        #endregion

        #region Events

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);
           // In This Case we load a UserControl
            m_RelatedCategoriesUC = Page.LoadControl("~/_CONTROLTEMPLATES/CustomField/RelatedCategoriesUC.ascx") as RelatedCategoriesUC;
            m_RelatedCategoriesUC.IsRequired = this.Field.Required;
        }

        protected override void CreateChildControls()
        {
            base.CreateChildControls();

            //load the usercontrol
            this.Controls.Add(m_RelatedCategoriesUC);
        }

        ///

        /// if the field is required,
        /// Make sure that at least one site was choosen
        /// by calling function Validate in the UserControl
        ///

        public override void Validate()
        {
            bool bIsValid = this.IsValid;

            if (this.ControlMode == SPControlMode.Display)
            {
                return;
            }

            base.Validate();

            if (this.IsValid && this.Field != null && this.Field.Required)
            {
                //if the field is required, call function Validate in the usercontrol
                //to make sure that the field is filled
                bIsValid = this.m_RelatedCategoriesUC.Validate();
            }

            if (bIsValid == false)
            {
                //field is not valid
                this.IsValid = false;
                //Init ErrorMessage from Rescource                                       
                this.ErrorMessage = oResource.GetValue("RequiredField_ChooseSite");

            }
            else
            {
                // The field is not empty or not required.
                // The data is valid.
            }
        }

        ///

        /// special care for display mode
        /// show urls and sequences if exisiting
        /// (the field is not required, so there can be no selections)
        ///

        ///
        protected override void RenderFieldForDisplay(System.Web.UI.HtmlTextWriter output)
        {
            RelatedCategoriesFieldValue oRelatedCategoriesFieldValue;
            string sHtml;

            if (this.ItemFieldValue != null)
            {
                //there is a selection- render it by calling function RenderFieldForDisplay of RelatedCategoriesUC
                sHtml = m_RelatedCategoriesUC.RenderFieldForDisplay(this.ItemFieldValue.ToString());
                output.Write(sHtml);
            }
            else
            {
                //no selection
                output.Write("none");
            }
        }


        #endregion
    }
}

Hope This Helps