asp向asp.net應用程序的轉變過程

2019-11-18 19:27:45

字體：大中小

來源：轉載

供稿：網友

下面示例中的第一個代碼塊對于某類 asp 應用程序是很典型的，該類應用程序使用 ADO 讀取和操作從單個 SQL 查詢返回的記錄集。它使用 ADO Recordset 對象讀取從用 Microsoft access 提供的 Northwind 示例數據庫返回的數據記錄。這些代碼將包含在具有 .asp 文件擴展名的文件中。
[Visual Basic]
<%@LANGUAGE=VBSCR ipT%>
<!
This ASP example uses ADO to read records from a database and PRint two
fields from all returned records to an ASP page. Connection to the Northwind database is through an ODBC system data source (DSN.
>
<html>
<body>
<%
 dim ADOconn, ADOrs, sqlstr
 sqlstr="SELECT * FROM Employees;"
 set ADOconn = Server.CreateObject("ADODB.Connection")
 ADOconn.Open "DSN = Test"
 set ADOrs = ADOconn.execute(sqlstr)
 if ADOrs.BOF and ADOrs.EOF then ' Query didn't return any records.
 Response.Write("No Records.")
 else
 ADOrs.MoveFirst
 Do While Not ADOrs.EOF
 Response.Write(ADOrs("FirstName") & " " _
 & ADOrs("LastName") & " ")
 ADOrs.MoveNext
 Loop
 Response.Write("End of data.")
 end if
 ADOrs.close
 set ADOrs = nothing
%>
</body>
</html>

下面的示例闡釋將前面示例轉換為 asp.net 應用程序所需的最低程度的更改。為了符合新的 Visual Basic 語法，大多數的更改都是必要的。此文件可以用 .aspx 文件擴展名重命名，并且將與 ASP.NET 一起運行。修改后的代碼行以粗體顯示。注意，在第一行上添加了具有 aspcompat=true 屬性的 <%@ Page > 指令。

[Visual Basic]
<%@Page aspcompat=true Language = VB%>
<!
This example uses ADO to read records from a database and print two
fields from all records in the database to an ASP.NET page.
The database is located on the server and connection is through an ODBC system data source (DSN.
>
<html>
<body>
<%
 dim objConn, rs, sqlstr
 sqlstr="SELECT * FROM Employees;"
 objConn = Server.CreateObject("ADODB.Connection") ' Set removed.
 objConn.Open("DSN=TEST") ' Parentheses added.
 rs = objConn.execute(sqlstr) ' Set statement removed.
 Response.Write("ADO Test")

if rs.BOF and rs.EOF then ' Query didn't return any records.
 Response.Write("No Records")
 else
 rs.MoveFirst
 Do While Not rs.EOF
 ' Specify Value property.
 Response.Write(rs("FirstName").Value _
 & " " & rs("LastName").Value & " ")
 rs.MoveNext
 Loop
 Response.Write("End of data")
 end if
 rs.close
 rs = nothing ' Set statement removed.
%>

下一個示例是一個 ASP.NET 應用程序，該程序使用 ADO.NET 從與前面示例相同的 Northwind 數據庫讀取記錄。這些代碼生成的輸出等效于前面示例的輸出，而且已被修改以符合 ASP.NET 代碼塊約定。

該示例創建一個 ADO.NET DataSet 對象，在此情況下此對象包含一個數據表，而該數據表的使用方式與 ADO 記錄集的使用方式幾乎相同。請注意，數據集可以由一個或多個構成內存駐留數據庫的 DataTables、DataRelations 和 Constraints 的集合組成，因此 ADO.NET 數據集比 ADO 記錄集靈活得多。

為了使用 ADO.NET，需要導入 System.Data 和 System.Data.OleDb 命名空間。如果數據源是 SQL Server 數據庫，則導入 System.Data.SqlClient 命名空間而不是 System.Data.OleDb。有關使用 ADO 和 SQL .NET 數據提供程序的連接對象的詳細信息，請參見管理連接。

[Visual Basic]
<%@Import Namespace="System.Data"%>
<%@Import Namespace="System.Data.OleDb"%>
<!
This example uses ADO.NET to read records from a database and print two
fields from all returned records to an ASP.NET page. The database
is located on the local server.
>
<html>
<Script Language=VB Runat=Server>
 Sub Page_Load(Sender As Object, e As EventArgs)
 Dim MyConnection As OleDbConnection
 Dim MyCommand As OleDbDataAdapter
 dim MyDataset As DataSet
 dim MyTable As DataTable
 dim loop1, numrows As Integer
 dim sqlstr As String

 sqlstr = "SELECT * FROM Employees;"

 ' Create a connection to the data source.
 MyConnection = New OleDbConnection("Provider=SQLOLEDB;" _
 & "server=localhost;"Integrated Security=SSPI;" _
 & "Initial Catalog=Northwind")

' Create a Command object with the SQL statement.
MyCommand = New OleDbDataAdapter(sqlstr, MyConnection)

' Fill a DataSet with data returned from the database.
 MyDataset = New DataSet
 MyCommand.Fill(MyDataset)

 ' Create a new DataTable object and assign to it
 ' the new table in the Tables collection.
 MyTable = New DataTable
 MyTable = MyDataset.Tables(0)
 ' Find how many rows are in the Rows collection
 ' of the new DataTable object.
 numrows = MyTable.Rows.Count
 If numrows = 0 then
 Response.Write("No records.")
 Else
 Response.Write("" & Cstr(numrows) & " records found.")
 For loop1 = 0 To numrows - 1
 ' Print the values of the two columns in the Columns
 ' collection for each row.
 Response.Write(MyTable.Rows(loop1).Item("FirstName") _
 & " " & MyTable.Rows(loop1).Item("LastName") & " ")
 Next loop1
 End If
 Response.Write("End of data.")
 End Sub
</Script>
</html>