http://developer.51cto.com 2009-04-09 14:42 GWPBrian.net cnblogs
我要評論()個(gè)人認(rèn)為學(xué)習(xí)LINQ法就是通過實(shí)例來學(xué)習(xí)。光看書本上的理論效率是很慢的。我將作一個(gè)簡單的web應(yīng)用程序，實(shí)現(xiàn)對數(shù)據(jù)的增刪改操作。用到大家都熟悉的Northwind數(shù)據(jù)庫。
一.引用命名空間
System.Data.Linq
System.Data.Linq.Mapping （需要在項(xiàng)目中先引用System.Data.Linq）
二.為數(shù)據(jù)庫表創(chuàng)建實(shí)體類
Table(Name="Employees")]
public class Employee
{
[Column(IsDbGenerated=true,IsPrimaryKey=true)]
public int EmployeeID { get; set; }
[Column(Name="FirstName",DbType="varchar(20)")]
public string FirstName { get; set; }
[Column(Name = "LastName", DbType = "varchar(20)")]
public string LastName { get; set; }
}
常用的屬性聲明，可以很好的描述表中字段的屬性：
Name: 字段的名稱
DbType: 字段的數(shù)據(jù)類型
IsDbGenerated: 是否自動生成
CanBeNull: 字段是否為空
Storage: 保存數(shù)據(jù)的類字段名
三.創(chuàng)建一個(gè)強(qiáng)類型的數(shù)據(jù)環(huán)境
我們的數(shù)據(jù)庫系統(tǒng)可能會和多種類型的數(shù)據(jù)源打交道，所以應(yīng)該使我們的程序有和數(shù)據(jù)源進(jìn)行創(chuàng)建連接的能力。這里我們將創(chuàng)建的NorthwindDb類繼承DataContext基類。DataContext類表示LINQ to SQL 框架的主入口點(diǎn)。
其中有相關(guān)的處理LINQ to SQL的類，方法等。
public class NorthwindDb:DataContext
{
public NorthwindDb(string connectionString):base(connectionString)
{
}
public Table Employee;
}
四.創(chuàng)建Web From
首先為GridView綁定數(shù)據(jù)
private void BindGridView(string criteria)
{
string strConn = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
NorthwindDb db = new NorthwindDb(strConn);
IEnumerable results;
if (criteria == string.Empty)
{
results=db.Employee.ToArray();
}
else
{
results = (from c in db.Employee
where c.FirstName.Contains(criteria)
select c).ToArray();
}
GridView1.DataSource = results;
GridView1.DataBind();
}
搜索按鈕只需將參數(shù)傳進(jìn)去即可BindGridView(TextBox1.Text);
如果選中了GridView中的某一行，則需要將選中的數(shù)據(jù)綁定到DetailsView 中進(jìn)行編輯使用。
private void BindDetailsView()
{
int employeeID = (int)GridView1.SelectedValue;
string strConn = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
NorthwindDb db = new NorthwindDb(strConn);
var results = from emp in db.Employee
where emp.EmployeeID == employeeID
select emp;
DetailsView1.DataSource = results;
DetailsView1.DataBind();
}
protected void GridView1_SelectedIndexChanging(object sender, GridViewSelectEventArgs e)
{
GridView1.SelectedIndex = e.NewSelectedIndex;
}
protected void GridView1_SelectedIndexChanged(object sender, EventArgs e)
{
int employeeID = (int)GridView1.SelectedValue;
string strConn = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
BindDetailsView();
}
接下來就是對數(shù)據(jù)的增刪改操作：
protected void DetailsView1_ItemUpdating(object sender, DetailsViewUpdateEventArgs e)
{
string strConn = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
NorthwindDb db = new NorthwindDb(strConn);
var results = from emp in db.Employee
where emp.EmployeeID == (int)DetailsView1.SelectedValue
select emp;
results.First().FirstName = ((TextBox)DetailsView1.Rows[1].Cells[1].Controls[0]).Text;
results.First().LastName = ((TextBox)DetailsView1.Rows[2].Cells[1].Controls[0]).Text;
db.SubmitChanges();
BindGridView(string.Empty);
}
protected void DetailsView1_ItemInserting(object sender, DetailsViewInsertEventArgs e)
{
string strConn = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
NorthwindDb db = new NorthwindDb(strConn);
Employee emp = new Employee();
emp.FirstName = ((TextBox)DetailsView1.Rows[1].Cells[1].Controls[0]).Text;
emp.LastName= ((TextBox)DetailsView1.Rows[2].Cells[1].Controls[0]).Text;
db.Employee.InsertOnSubmit(emp);
db.SubmitChanges();
BindGridView(string.Empty);
}
protected void DetailsView1_ItemDeleting(object sender, DetailsViewDeleteEventArgs e)
{
string strConn = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
NorthwindDb db = new NorthwindDb(strConn);
var results = db.Employee.Single(emp => emp.EmployeeID==(int)DetailsView1.SelectedValue);
db.Employee.DeleteOnSubmit(results);
db.SubmitChanges();
BindGridView(string.Empty);
}
更新和添加的操作差不多，只是作了些小的改動。
ok，這就是在ASP.NET中利用LINQ對數(shù)據(jù)的操作。
