LinQ To Entity的增删改查

本示例程序采用Northwind 示例数据库，下面开始编写代码对Customers表进行增、删、改、查等等操作。

1.新增Customers记录
using (NorthwindEntities myDb = new NorthwindEntities())
{
Customers customer = new Customers();

Random rm = new Random();

customer.CustomerID = "A" + rm.Next(9999).ToString();
customer.CompanyName = "EntLib.com Forum";
customer.Address = "http://www.EntLib.com";

myDb.AddToCustomers(customer);

int count = myDb.SaveChanges();

txtCustomerID.Text = customer.CustomerID;
}

2.更新Customers记录
using (NorthwindEntities myDb = new NorthwindEntities())
{
var query = from customer in myDb.Customers
where customer.CustomerID == txtCustomerID.Text.Trim()
select customer;

foreach (var row in query)
{
row.CompanyName = "Updated Company Name";
}

myDb.SaveChanges();
}

3.删除Customers记录
using (NorthwindEntities myDb = new NorthwindEntities())
{
var query = from customer in myDb.Customers
where customer.CustomerID == txtCustomerID.Text.Trim()
select customer;

foreach (var row in query)
{
myDb.DeleteObject(row);
}

myDb.SaveChanges();
}

4.查询Customers，返回所有记录
using (NorthwindEntities myDb = new NorthwindEntities())
{
dataGridView1.DataSource = myDb.Customers;
}