 Using a transacted C# component (leveraging COM+)
发信人: Jobs (温少), 信区: DotNET
标 题: Using a transacted C# component (leveraging COM+)
发信站: BBS 水木清华站 (Wed May 9 00:04:56 2001)
Using a transacted C# component (leveraging COM+) from ASP.NET
Scott Guthrie
January 4, 2001
Level: Beginner/Intermediate
Several people have asked questions like "is COM+ dead", "how does
COM+ relate to .NET", etc. The answer is that COM+ is definitely not
gone. It remains and will continue to be an important part of the
overall programming model, and it can be fully leveraged from ASP.NET
and the overall .NET Framework. You can continue to create COM+
components using VS6 and other compilers and then call them from ASP.NET
pages. You can also take advantage of COM+ services with new classes
built using the .NET Framework.
You will find that leveraging these services, for example: COM+
transactions and COM+ object pooling, has become a whole lot easier
using ASP.NET and the .NET Framework. For example, it is now possible to
avoid having to manually install a transacted component using the
COM+ Component Services Administration tool. Instead, if you want a
component to support transactions, you can simply add a "Transaction"
attribute to the top of a class and copy the compiled component into the
"bin" directory of your ASP.NET web application. When the class is
first activated, it will automatically be registered with COM+ for you,
which means "xcopy deployment" of both non-transacted and transacted
components.
You can also now take advantage of the COM+ "AutoComplete" feature
within your .NET components simply by marking activating methods
within an "AutoComplete" attribute. Assuming no exceptions get thrown
during the method's execution -- the transaction will automatically
commit for you. If you want to force termination of a transaction,
simply raise or throw an exception to abort it.
The below sample demonstrates how to build a simple transacted C#
class and use it within an ASP.NET page written using VB. Note that I've
only tried this on Win2k; I'm not sure whether this works on NT4 in
beta1:
Account.cs:
using System;
using Microsoft.ComServices;
// COM+ app name as it appears in the COM+ catalog
[assembly: ApplicationName("TestApp")]
[Transaction(TransactionOption.Required)]
public class Account : ServicedComponent
{
[AutoComplete]
public String Debit(int amount)
{
// Todo: Do some Database work, throw an
// exception to abort the transaction.
// otherwise the transaction will commit.
// Use the ContextUtil class to return the
// transaction id
return ContextUtil.TransactionId.ToString();
}
}
To compile the above class, simply execute the following code within the
root directory of an ASP.NET application:
mkdir bin
csc /target:library /out:bin\Account.dll Account.cs
/r:Microsoft.ComServices.dll
then invoke the component from the following ASP.NET Page (no
registration required):
Trans.aspx:
<html>
<script language="VB" runat=server>
Sub Page_Load(Sender As Object, E as EventArgs)
Dim MyAccount as New Account()
TransId.Text = MyAccount.Debit(343)
End Sub
</script>
<body>
<h1>C# Transacted Component within ASP.NET</h1>
<b> Transaction ID: </b> <asp:label id="TransId" runat=server/>
</body>
</html>
The transaction id of the completed transaction should be rendered
cleanly into the output. To see how the COM+ auto-registration mechanism
worked, open up the "Component Services" admin tool within the
"Programs->Administrative Tools" item on the Start Menu. Expand the
"Component Services" tab to "Computers->My Computer" and then to "COM+
Applications".
Notice the presence of the "TestApp" COM+ Application/Package. This
was created in response to line 4 of the Account.cs file (which had an
assembly attribute indicating the COM+ App name to create). Expand
this to see the "Account" component listed within it. Notice that the
properties of the component (for example: transaction=required) within
the admin tool match those set within the Account.cs file.
Then click on the "Distributed Transaction Coordinator->Transaction
Statistics" item within the admin tool. Notice that the transaction
count increases each time you hit the page.
Note that the above sample demonstrates calling a transacted component
from a non-transacted ASP.NET Page. Note that if you want the ASP.NET
page itself to be transacted as well (for example: if you were calling
multiple transacted components from it and wanted them to all share
the same transaction), simply add the <%@ Page Transaction="Required" %>
attribute to the top of the file.
--
※ 来源:·BBS 水木清华站 smth.org·[FROM: 210.39.3.110]
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