一、用LINQ技术查询关系型数据库，需要使用LINQ to ADO.NET
分为：LINQ to sql,LINQ to Dataset ，LINQ to Entities
LINQ to sql 是通过开发者建立一个映射sqlserver中的数据表，被称作实体类的类型，来完成对数据库的查询、修改、删除等操作
LINQ to Dataset 用来查询Dataset 或从数据库断开连接的数据表
LINQ to Entities的用途跟LINQ to sql 类似，但比LINQ to sql 功能要更加复杂和强大。ex:在一个实体类中映射多个数据表格和他们的关系，以及查询除sqlserver 系列产品以外的关系数据库等。注：LINQ to Entities 需要安装ServerPack 才能使用
二、.实例：
1.数据库里新建一个表（比如一个人的姓名，年龄，住址，职位等通讯簿信息。）表名：TabAddressBook
2.新建一个LINQ-sql 的类，后缀名为.dbml，名称为：AddressBookClasses
3.在服务器资源管理器，中把该表格拖到AddressBookClasses.dbml文件上，保存；
接下来我们需要写一个类是用来把界面和LINQ-sql搭建起来，实现一个通讯录的新增，删除，保存
代码如下：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
namespace MainForm
{
/// <summary>
/// 电话簿类(负责用(LINQ to sql)在界面和数据库之间进行数据传递）
/// </summary>
class AddressBookController
{
/// <summary>
/// LINQ to sql 数据库上下文
/// </summary>
public AddressBookClassesDataContext dataContext;
/// <summary>
/// 提供给控件的数据绑定对象
/// </summary>
public IBindingList BookBindingList { get; private set; }
public AddressBookController()
{
this.dataContext = new AddressBookClassesDataContext();
this.BookBindingList = this.dataContext.TabAddressBook.GetNewBindingList();
}
/// <summary>
/// 析构函数
/// </summary>
~AddressBookController()
{
if (this.dataContext != null)
this.dataContext.dispose();
}
/// <summary>
/// 增加
/// </summary>
/// <param name="item"></param>
public void New(TabAddressBook item)
{
if (item != null)
{
this.dataContext.TabAddressBook.InsertOnSubmit(item);
this.dataContext.SubmitChanges();
this.BookBindingList = this.dataContext.TabAddressBook.GetNewBindingList();
}
}
/// <summary>
/// 修改
/// </summary>
/// <param name="item"></param>
public void Update(TabAddressBook item)
{
if (item != null)
{
var query = from i in this.dataContext.TabAddressBook where i.ab_id == item.ab_id select i;
foreach (var q in query)
{
q.ab_add = item.ab_add;
q.ab_age = item.ab_age;
q.ab_com = item.ab_com;
q.ab_position = item.ab_position;
q.ab_name = item.ab_name;
q.ab_sex = item.ab_sex;
q.ab_tel = item.ab_tel;
}
this.dataContext.SubmitChanges();
this.BookBindingList = this.dataContext.TabAddressBook.GetNewBindingList();
}
}
/// <summary>
/// 删除
/// </summary>
/// <param name="item"></param>
public void Delete(TabAddressBook item)
{
if (item != null)
{
var query = from v in this.dataContext.TabAddressBook where v.ab_id == item.ab_id select v;
foreach (var q in query)
this.dataContext.TabAddressBook.DeleteOnSubmit(q);
this.dataContext.SubmitChanges();
this.BookBindingList = this.dataContext.TabAddressBook.GetNewBindingList();
}
}
/// <summary>
/// 搜所
/// </summary>
/// <param name="p"></param>
/// <returns></returns>
public IEnumerable<TabAddressBook> Search(string p)
{
var query = from v in this.dataContext.TabAddressBook where v.ab_name.IndexOf(p) > -1 select v;
return query;
}
}
}
界面如下：
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace MainForm
{
public partial class Form1 : Form
{
/// 初始化电话簿控制类
private AddressBookController abc = new AddressBookController();
//存储正在操作的数据
private TabAddressBook NowItem = null;
public Form1()
{
InitializeComponent();
Bindct(abc.BookBindingList);
}
/// <summary>
/// 控件数据绑定
/// </summary>
/// <param name="datasource"></param>
private void Bindct(object datasource)
{
this.lstAdd.DataSource = null;
this.lstAdd.DataSource = datasource;
this.lstAdd.displayMember = "ab_name";
this.txtAge.DataBindings.Clear();
this.txtAge.DataBindings.Add(new Binding("Text",datasource,"ab_age",true));
this.txtName.DataBindings.Clear();
this.txtName.DataBindings.Add(new Binding("Text","ab_name"));
this.txtAddress.DataBindings.Clear();
this.txtAddress.DataBindings.Add(new Binding("Text","ab_add"));
this.txtCompany.DataBindings.Clear();
this.txtCompany.DataBindings.Add(new Binding("Text","ab_com"));
this.txtPosition.DataBindings.Clear();
this.txtPosition.DataBindings.Add(new Binding("Text","ab_position"));
this.txtTel.DataBindings.Clear();
this.txtTel.DataBindings.Add(new Binding("Text","ab_tel"));
this.cbSex.DataBindings.Clear();
this.cbSex.DataBindings.Add(new Binding("Text","ab_sex"));
}
/// <summary>
/// 新建 /// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnAdd_Click(object sender,EventArgs e)
{
TabAddressBook tb = new TabAddressBook() { ab_name = txtName.Text,ab_add = txtAddress.Text,ab_position = txtPosition.Text,ab_com = txtCompany.Text,ab_tel = txtTel.Text,ab_sex = cbSex.SelectedText,ab_age = Convert.ToByte(txtAge.Text) };
this.NowItem = tb;
this.abc.New(tb);
this.Bindct(abc.BookBindingList);
}
/// <summary>
/// 保存
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnSave_Click(object sender,EventArgs e)
{
this.NowItem = this.lstAdd.SelectedItem as TabAddressBook;
TabAddressBook tb = new TabAddressBook() {ab_id = this.NowItem.ab_id,ab_name = txtName.Text,ab_age = Convert.ToByte(txtAge.Text) };
this.NowItem = tb;
this.abc.Update(tb);
this.Bindct(abc.BookBindingList);
}
/// <summary>
/// 删除 /// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btnDelete_Click(object sender,EventArgs e)
{
//转到控制器中使用LINQ to sql 从数据库删除
if (this.lstAdd.SelectedItem != null)
{
this.abc.Delete((TabAddressBook)this.lstAdd.SelectedItem);
this.Bindct(abc.BookBindingList);
}
}
private void txtSearch_TextChanged(object sender,EventArgs e)
{
if (this.txtSearch.Text.Length > 0)
{
//使用LINQ搜索
IEnumerable<TabAddressBook> book = this.abc.Search(this.txtSearch.Text);
this.Bindct(book);
}
}
}
}
版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 [email protected] 举报，一经查实，本站将立刻删除。
