LINQ to SQL 可以做到的功能
LINQ to SQL 支援 SQL 開發人員需要的所有重要功能。 您可以查詢資訊，以及在資料表中插入、更新和刪除資訊。
選取
選取 (「投影」(Projection)) 的方式很簡單，只要以您自己的程式語言撰寫 LINQ 查詢，再執行該查詢來擷取結果即可。 LINQ to SQL 會將所有必要的作業轉譯成熟悉的 SQL 作業。 如需詳細資訊，請參閱 LINQ to SQL。
在下列範例中，會擷取 London 客戶的公司名稱，並將它們顯示在主控台視窗中。
' Northwnd inherits from System.Data.Linq.DataContext.
Dim nw As New Northwnd("c:\northwnd.mdf")
' or, if you are not using SQL Server Express
' Dim nw As New Northwnd("Database=Northwind;Server=dschwart7;Integrated Security=SSPI")
Dim companyNameQuery = _
From cust In nw.Customers _
Where cust.City = "London" _
Select cust.CompanyName
For Each customer In companyNameQuery
Console.WriteLine(customer)
Next
// Northwnd inherits from System.Data.Linq.DataContext.
Northwnd nw = new Northwnd(@"northwnd.mdf");
// or, if you are not using SQL Server Express
// Northwnd nw = new Northwnd("Database=Northwind;Server=server_name;Integrated Security=SSPI");
var companyNameQuery =
from cust in nw.Customers
where cust.City == "London"
select cust.CompanyName;
foreach (var customer in companyNameQuery)
{
Console.WriteLine(customer);
}
插入
若要執行 SQL Insert，只要將物件加入至所建立的物件模型，並在 DataContext 上呼叫 SubmitChanges 即可。
在下列範例中，會使用 InsertOnSubmit 將新的客戶與該客戶的相關資訊加入至 Customers 資料表。
' Northwnd inherits from System.Data.Linq.DataContext.
Dim nw As New Northwnd("c:\northwnd.mdf")
Dim cust As New Customer With {.CompanyName = "SomeCompany", _
.City = "London", _
.CustomerID = 98128, _
.PostalCode = 55555, .Phone = "555-555-5555"}
nw.Customers.InsertOnSubmit(cust)
' At this point, the new Customer object is added in the object model.
' In LINQ to SQL, the change is not sent to the database until
' SubmitChanges is called.
nw.SubmitChanges()
// Northwnd inherits from System.Data.Linq.DataContext.
Northwnd nw = new Northwnd(@"northwnd.mdf");
Customer cust = new Customer();
cust.CompanyName = "SomeCompany";
cust.City = "London";
cust.CustomerID = "98128";
cust.PostalCode = "55555";
cust.Phone = "555-555-5555";
nw.Customers.InsertOnSubmit(cust);
// At this point, the new Customer object is added in the object model.
// In LINQ to SQL, the change is not sent to the database until
// SubmitChanges is called.
nw.SubmitChanges();
更新
若要更新 (Update) 資料庫項目，請先擷取該項目，然後直接在物件模型中編輯該項目。 修改物件之後，再於 DataContext 上呼叫 SubmitChanges 以更新資料庫。
在下列範例中，會擷取所有來自 London 的客戶， 然後將城市的名稱從 "London" 變更為 "London - Metro"。 最後，會呼叫 SubmitChanges，以將變更傳送至資料庫。
Dim nw As New Northwnd("c:\northwnd.mdf")
Dim cityNameQuery = _
From cust In nw.Customers _
Where cust.City.Contains("London") _
Select cust
For Each customer In cityNameQuery
If customer.City = "London" Then
customer.City = "London - Metro"
End If
Next
nw.SubmitChanges()
Northwnd nw = new Northwnd(@"northwnd.mdf");
var cityNameQuery =
from cust in nw.Customers
where cust.City.Contains("London")
select cust;
foreach (var customer in cityNameQuery)
{
if (customer.City == "London")
{
customer.City = "London - Metro";
}
}
nw.SubmitChanges();
刪除
若要刪除 (Delete) 項目，請從項目所屬的集合中移除該項目，然後在 DataContext 上呼叫 SubmitChanges，以認可變更。
.gif "注意事項") 注意事項 |
|---|
LINQ to SQL 無法辨識串聯刪除作業。如果您要刪除有條件約束之資料表中的資料列，請參閱 HOW TO：從資料庫刪除資料列 (LINQ to SQL)。 |
在下列範例中，會從資料庫中擷取 CustomerID 為 98128 的客戶。 然後會在確認已擷取該客戶的資料列之後，呼叫 DeleteOnSubmit，以從集合中移除該物件。 最後，會呼叫 SubmitChanges，以將刪除轉送至資料庫。
Dim nw As New Northwnd("c:\northwnd.mdf")
Dim deleteIndivCust = _
From cust In nw.Customers _
Where cust.CustomerID = 98128 _
Select cust
If deleteIndivCust.Count > 0 Then
nw.Customers.DeleteOnSubmit(deleteIndivCust.First)
nw.SubmitChanges()
End If
Northwnd nw = new Northwnd(@"northwnd.mdf");
var deleteIndivCust =
from cust in nw.Customers
where cust.CustomerID == "98128"
select cust;
if (deleteIndivCust.Count() > 0)
{
nw.Customers.DeleteOnSubmit(deleteIndivCust.First());
nw.SubmitChanges();
}