protected void Button1_Click(object sender, EventArgs e)
{
//查询部分列
//通过在select中加入匿名类
StudyEntities db = null;
if (HttpContext.Current.Items["db"] == null)
{
db = new StudyEntities();
HttpContext.Current.Items["db"] = db;
}
else
{
db = HttpContext.Current.Items["db"] as StudyEntities;
}
var userInfoList = from u in db.UserInfo
where u.UserId == 1039
select new { UName = u.UserName, UPwd = u.UserPwd };
foreach (var item in userInfoList)
{
Response.Write(item.UName);
//Response.Write(UserInfo.)
}
}
/// <summary>
/// 删除
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button4_Click(object sender, EventArgs e)
{
StudyEntities studyEntities = new StudyEntities();
//var userInfoList = from u in studyEntities.UserInfo
// where u.UserId == 1166
// select u;
//UserInfo userInfo = userInfoList.FirstOrDefault();//返回第一个元素，如果没有则返回NULL
//if (userInfo != null)
//{
// //studyEntities.UserInfo.Remove(userInfo);
// studyEntities.Entry<UserInfo>(userInfo).State = EntityState.Deleted;
// studyEntities.SaveChanges();
//}
//else
//{
// Response.Write("删除的数据不存在");
//}
//若要用Remove 则UserInfo对象需从EF中获取才可用；
//而通过设置State的方式则不需要如此；
UserInfo userInfo = new UserInfo()
{
UserId = 1162
};
//studyEntities.UserInfo.Remove(userInfo);
studyEntities.Entry <UserInfo>(userInfo).State = EntityState.Deleted;
studyEntities.SaveChanges();
}
protected void Button4_Click(object sender, EventArgs e)
{
StudyEntities db = new StudyEntities();
var userInfoList = db.UserInfo.Where(u => u.UserId > 0).ToList();
int i = 0;
int count = userInfoList.Count();
Response.Write(count);
}
/// <summary>
/// 更新
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button5_Click(object sender, EventArgs e)
{
StudyEntities db = new StudyEntities();
var userInfoList = from u in db.UserInfo
where u.UserId == 1163
select u;
var userInfo = userInfoList.FirstOrDefault();
userInfo.UserPwd = "666666";
db.Entry <UserInfo>(userInfo).State = EntityState.Modified;
db.SaveChanges();
}
protected void Button2_Click(object sender, EventArgs e)
{
//查询
StudyEntities studyEntities = new StudyEntities();
//linq表达式
var userInfoList = from u in studyEntities.UserInfo
where u.UserId == 1166
select u;
int i = 0;
//延迟加载机制 数据使用到的时候吗，才会进行查询，否则不会进行查询
foreach (var item in userInfoList)
{
Response.Write(item.UserName);
}
}
/// <summary>
/// 分页排序查询
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
protected void Button2_Click(object sender, EventArgs e)
{
StudyEntities db = new StudyEntities();
int pageIndex = 2;
int pageSize = 2;
//排序OrderBy 分页 Skip(跳过几条数据)Take(取出几条数据)
var userInfoList = db.UserInfo.Where(t => t.UserId > 0).OrderByDescending(u => u.UserId).ThenByDescending(t => t.UserPwd).Skip((pageIndex - 1) * pageIndex).Take(pageSize);
//var userInfoList = (from u in db.UserInfo
// where u.UserId > 0
// orderby u.UserId ascending//descending降序
// select u).Skip((pageIndex - 1) * pageIndex).Take(pageSize);//分页与lambda表达式一样的处理
foreach (var item in userInfoList)
{
Response.Write(item.UserName);
}
}
protected void Button1_Click(object sender, EventArgs e)
{
//新增
UserInfo userInfo = new UserInfo();
userInfo.UserName = "******";
userInfo.UserPwd = "123456";
userInfo.RegDate = DateTime.Now;
StudyEntities db = new StudyEntities();
//将数据添加到EF 并且添加了添加标记(Add)
db.UserInfo.Add(userInfo);
//更新到数据库
//返回受影响的行数
db.SaveChanges();
Response.Write(userInfo.UserId);
}