设置列表字段为主键

转贴:Sample event handler to set a field as a pr imary key (enforce no duplicates)

Got this as a request from a reader- how to prevent users from adding items with same titles as ones that already exist in the list.

Code

using System;

using System.Collections.Generic;

using System.Text;

using Microsoft.SharePoint;

namespace SPSTIPS.SharePoint.EventHandlers

{

    public class TitlePrimaryEventHandler:SPItemEventReceiver

    {

        const string TITLE_QUERY = @"<Query><Where><Eq><FieldRef Name=""Title"" /><Value Type=""Text"">{0}</Value></Eq></Where></Query>";

        public override void ItemAdding(SPItemEventProperties properties)

        {

            if (properties.AfterProperties["Title"] != null)

            {

                //get the title of the new item

                string currentTitle = properties.AfterProperties["Title"].ToString();

                //get the web site object

                using (SPWeb web = properties.OpenWeb())

                {

                     //get the current list

                    SPList list = web.Lists[properties.ListId];

                    //query the list to check if there are items with the same title

                    SPQuery q = new SPQuery();

                    q.Query = string.Format(TITLE_QUERY, currentTitle);

                    SPListItemCollection itemsWithSameTitle = list.GetItems(q);

                    //if there are items, cancel the add, and show an error to the user.

                    if (itemsWithSameTitle.Count > 0)

                    {

                        properties.Cancel = true;

                        properties.ErrorMessage = "There is already an item with the title \"" + currentTitle + "\" in this list\".";

                    }

                }

            }

        }

    }

}






上面的代码中，已经写了使用方法，就是用SPWeb web = properties.OpenWeb()