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period. If this is the case, an event will be triggered only when the state at the end of the period differs

from the state at the beginning of the period. For example, no event is raised if a process is started

and then stopped within a single polling interval.

The event handler constructs a new

ManagementBaseObject from a value passed into

the event arguments to obtain the display name and

executable path of the new process. Since UI controls

can only be updated from the UI thread, you cannot

directly update the ListBox. Instead you must call

BeginInvoke to execute the LogNewProcess function

on the UI thread. Figure 9-9 shows the form in action.

Message queues

The Message Queues node, expanded in Figure 9-10, gives you access to the message queues

available on your computer. You can use three types of queues: private, which will not appear when

a foreign computer queries your computer; public, which will appear; and system, which is used for

unsent messages and other exception reporting.

fiGure 9-9

To use the Message Queues node, you need to ensure that MSMQ is installed on

your computer. You can do this via Programs and Features in the Control Panel.

Select the Turn Windows Features On or Off task menu item and then select the

checkbox to enable the Microsoft Message Queue (MSMQ) Server feature.

In Figure 9-10, a message queue called samplequeue has been added

to the Private Queues node by selecting Create Queue from the

right-click context menu. Once you have created a queue, you can

create a properly configured instance of the MessageQueue class

by dragging the queue onto a new Windows Form. To demonstrate

the functionality of the MessageQueue object, add two TextBoxes

and a button to the form, laid out as shown in Figure 9-11. The

Send button is wired up to use the MessageQueue object to send the

message entered in the first textbox. In the Load event for the form,

a background thread is created that continually polls the queue to

retrieve messages, which will populate the second textbox:

c#

public Form4()

{

InitializeComponent();

var monitorThread = new System.Threading.Thread(MonitorMessageQueue);

fiGure 9-10

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monitorThread.IsBackground = true;

monitorThread.Start();

this.Button1.Click +=new EventHandler(btn_Click);

}

private void btn_Click(object sender, EventArgs e)

{

this.messageQueue1.Send(this.TextBox1.Text);

}

private void MonitorMessageQueue()

{

var m = default(System.Messaging.Message);

while (true)

{

try

{

m = this.messageQueue1.Receive(new TimeSpan(0, 0, 0, 0, 50));

this.ReceiveMessage((string)m.Body);

}

catch (System.Messaging.MessageQueueException ex)

{

if (!(ex.MessageQueueErrorCode ==

System.Messaging.MessageQueueErrorCode.IOTimeout))

{

throw ex;

}

}

System.Threading.Thread.Sleep(10000);

}

}

private delegate void MessageDel(string msg);

private void ReceiveMessage(string msg)

{

if (this.InvokeRequired)

{

this.BeginInvoke(new MessageDel(ReceiveMessage), msg);

return;

}

this.TextBox2.Text = msg;

}

Code snippet Form4.cs

Vb

Private Sub Form_Load(ByVal sender As Object, ByVal e As System.EventArgs) _

Handles Me.Load

Dim monitorThread As New Threading.Thread(AddressOf MonitorMessageQueue)

monitorThread.IsBackground = True

monitorThread.Start()

End Sub

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169

Private Sub btn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) _

Handles Button1.Click

Me.MessageQueue1.Send(Me.TextBox1.Text)

End Sub

Private Sub MonitorMessageQueue()

Dim m As Messaging.Message

While True

Try

m = Me.MessageQueue1.Receive(New TimeSpan(0, 0, 0, 0, 50))

Me.ReceiveMessage(m.Body)

Catch ex As Messaging.MessageQueueException

If Not ex.MessageQueueErrorCode = _

Messaging.MessageQueueErrorCode.IOTimeout Then

Throw ex

End If

End Try

Threading.Thread.Sleep(10000)

End While

End Sub

Private Delegate Sub MessageDel(ByVal msg As String)

Private Sub ReceiveMessage(ByVal msg As String)

If Me.InvokeRequired Then

Me.BeginInvoke(New MessageDel(AddressOf ReceiveMessage), msg)

Return

End If

Me.TextBox2.Text = msg

End Sub

Code snippet Form4.vb

Note in this code snippet that the background thread is

never explicitly closed. Because the thread has the

IsBackground property set to True, it is automatically

terminated when the application exits. As with the

previous example, because the message processing is done

in a background thread, you need to switch threads when

you update the user interface using the BeginInvoke

method. Putting this all together, you get a form like the

one shown in Figure 9-11.

As messages are sent to the message queue, they appear

under the appropriate queue in Server Explorer. Clicking

the message displays its contents in the Properties window.

Performance counters

One of the most common things developers forget to consider when building an application is how

it will be maintained and managed. For example, consider an application that was installed a year

fiGure 9-11

170 .

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ago and has been operating without any issues. All

of a sudden, requests start taking an unacceptable

amount of time. It is clear that the application is not

behaving correctly, but there is no way to determine

the cause of the misbehavior. One strategy for

identifying where the performance issues are is

to use performance counters. Windows has many

built-in performance counters that can be used to

monitor operating system activity, and a lot of third-

party software also installs performance counters so

administrators can identify any rogue behavior.

The Performance Counters node in the Server

Explorer tree, expanded in Figure 9-12, has two

primary functions. First, it enables you to view

and retrieve information about the currently

installed counters. You can also create new

performance counters, as well as edit or delete existing counters. As you can see in Figure 9-12,

under the Performance Counters node is a list of categories and under those is a list of counters.

fiGure 9-12

You must be running Visual Studio with Administrator rights to view the

Performance Counters under the Server Explorer.

To edit either the category or the counters, select

Edit Category from the right-click context menu

for the category. To add a new category and

associated counters, right-click the Performance

Counters node and select Create New Category

from the context menu. Both of these operations

use the dialog shown in Figure 9-13. Here, a new

performance counter category has been created

that will be used to track a form’s open and

close events.

The second function of the Performance Counters

section is to provide an easy way for you to access

performance counters via your code. By dragging

a performance counter category onto a form, you

gain access to read and write to that performance

counter. To continue with this chapter’s example,

drag the new My Application performance

counters, Form Open and Form Close, onto a new

fiGure 9-13

Windows Form. Also add a couple of textboxes and a button so you can display the performance

counter values. Finally, rename the performance counters so they have friendly names. This should

give you a form similar to the one shown in Figure 9-14.

server Connections .

171

fiGure 9-14

In the properties for the selected performance counter, you can see that the appropriate counter — in

this case, Form Close — has been selected from the My Application category. You will also notice a

MachineName property, which is the computer from which you are retrieving the counter information,

and a ReadOnly property, which needs to be set to False if you want to update the counter. (By

default, the ReadOnly property is set to True.) To complete this form, add the following code to the

Retrieve Counters button click event handler:

c#

this.textBox1.Text = this.perfFormOpen.RawValue.ToString();

this.textBox2.Text = this.perfFormClose.RawValue.ToString();

Code snippet Form5.cs

Vb

Me.textBox1.Text = Me.perfFormOpen.RawValue

Me.textBox2.Text = Me.perfFormClose.RawValue

Code snippet Form5.vb

You also need to add code to the application to update the performance counters. For example, you

might have the following code in the Form Load event handlers:

c#

this.perfFormOpen.Increment();

Vb

Me.perfFormOpen.Increment()

When you dragged the performance counter onto the form, you may have noticed a smart tag (small

arrow that appears near the top-right corner when a control is selected) on the performance counter

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component that had a single item, Add Installer. When the component is selected, as in

Figure 19-14, you will notice the same action at the bottom of the Properties window. Clicking

this action in either place adds an Installer class to your solution that can be used to install the

performance counter as part of your installation process. Of course, for this installer to be called,

the assembly it belongs to must be added as a custom action for the deployment project. For more

information on custom actions, see Chapter 48.

Prior to Visual Studio 2008, you needed to manually modify the installer to create multiple

performance counters. In the current version, you can simply select each additional performance

counter and click Add Installer. Visual Studio 2010 will direct you back to the first installer that

was created and will have automatically added the second counter to the Counters collection of the

PerformanceCounterInstaller component, as shown in Figure 9-15.

fiGure 9-15

You can also add counters in other categories by adding

additional PerformanceCounterInstaller components

to the design surface. You are now ready to deploy your

application with the knowledge that you will be able to use

a tool such as PerfMon to monitor how your application is

behaving.

services

The Services node, expanded in Figure 9-16, shows the

registered services for the computer. Each node indicates

the state of that service in the bottom-right corner of the

icon. Possible states are Stopped, Running, or Paused.

Selecting a service displays additional information about the

service, such as other service dependencies, in the Properties

fiGure 9-16

window.

Data Connections .

173

As with other nodes in the Server Explorer, each service can be dragged onto the design surface

of a form. This generates a ServiceController component in the nonvisual area of the form. By

default, the ServiceName property is set to the service that you dragged across from the Server

Explorer, but this can be changed to access information and control any service. Similarly, the

MachineName property can be changed to connect to any computer to which you have access. The

following code shows how you can stop a Service using ServiceController component:

c#

this.serviceController1.Refresh();

if (this.serviceController1.CanStop)

{

if (this.serviceController1.Status ==

System.ServiceProcess.ServiceControllerStatus.Running)

{

this.serviceController1.Stop();

this.serviceController1.Refresh();

}

}

Code snippet Form6.cs

Vb

Me.ServiceController1.Refresh()

If Me.ServiceController1.CanStop Then

If Me.ServiceController1.Status = _

ServiceProcess.ServiceControllerStatus.Running Then

Me.ServiceController1.Stop()

Me.ServiceController1.Refresh()

End If

End If

Code snippet Form6.vb

In addition to the three main states — Running, Paused, or Stopped — other transition states

are ContinuePending, PausePending, StartPending, and StopPending. If you are about to start a

service that may be dependent on another service that is in one of these transition states, you can

call the WaitForStatus method to ensure that the service will start properly.

data connections

The Data Connections node allows you to connect to a database and perform a large range of

administrative functions. You can connect to a wide variety of data sources including any edition

of SQL Server, Microsoft Access, Oracle, or a generic ODBC data source. Figure 9-17 shows the

Server Explorer connected to a SQL Server database file.

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The Server Explorer provides access to the Visual

Database, which will allow you to perform a large range of

administrative functions on the connected database. You can

create databases, add and modify tables, views, and stored

procedures, manage indexes, execute queries, and much

more. Chapter 26 covers all aspects of the Data Connections

functionality.

sharePoint connections

New to Visual Studio 2010 is the ability to connect to a

Microsoft Office SharePoint Server with the Server Explorer.

This feature allows you to navigate and view many of the

SharePoint resources and components.

The Server Explorer only provides read-only access to

SharePoint resources — you cannot, for example, create or

edit a list definition. Even so, it can be useful to have ready

access to this information in Visual Studio when developing a

SharePoint application. As with many of the components under the Servers Node you can also drag

and drop certain SharePoint resources directly onto the design surface of your SharePoint project.

Using the Server Explorer to browse SharePoint resources is covered in detail in Chapter 24.

suMMary

In this chapter you learned how the Server Explorer can be used to manage and work with computer

resources and services. Chapter 22 continues the discussion on the Server Explorer, covering