Ever felt like your C/C++ application is a black box, with no easy way to see what’s happening under the hood? Performance counters can be your x-ray vision, revealing bottlenecks, resource hogs, and hidden inefficiencies. While Windows provides some built-in counters, they often fall short. In this guide, we’ll unlock the power of custom performance counters, giving you the tools to track exactly what matters most in your code.

What’s the Big Deal with Performance Counters?

Think of them as dials and gauges for your application’s engine. They measure things like:

• How fast specific functions are running
• How much memory your application is consuming
• How often certain events are occurring

This data is invaluable for diagnosing performance problems and making your code leaner and faster.

Why Roll Your Own?

Built-in counters are convenient, but they’re one-size-fits-all. By crafting custom counters, you can:

• Track metrics specific to your application’s logic
• Gain deeper insights into custom components or libraries
• Integrate seamlessly with your existing monitoring tools

Let’s Get Our Hands Dirty: Building Custom Counters

Before we dive in, you’ll need a basic understanding of C/C++ programming and the Windows API. Don’t worry, we’ll break it down step by step:

1. Design Your Performance Counters

First, decide what you want to measure. Some examples:

• The number of times a specific function is called
• The average time spent in a particular code block
• The amount of data processed per second

Choose appropriate counter types (e.g., number of items, rate of change, average) and names that make sense.

2. Coding Time!

Here’s a simplified example of how to create a custom counter using the Windows API:

#include <windows.h>
#include <pdh.h>

PDH_HQUERY   query;
PDH_HCOUNTER counter;

// Create a query
PdhOpenQuery(NULL, 0, &query);

// Add your custom counter to the query
PdhAddCounter(query, "\\YourCategoryName\\YourCounterName", 0, &counter);

// Start collecting data
PdhCollectQueryData(query);

// ... (Run your application and gather data)

// Get the counter value
PDH_FMT_COUNTERVALUE counterValue;
PdhGetFormattedCounterValue(counter, PDH_FMT_DOUBLE, NULL, &counterValue);

// Print the value (or log it, etc.)
printf("Counter value: %f\n", counterValue.doubleValue);

This code does the following:

1. Opens a performance query.

2. Adds your custom counter to the query (you’ll need to replace placeholders with your actual category and counter names).

3. Starts collecting data.

4. Retrieves the counter value (after some time has passed).

5. View Your Masterpiece

The easiest way to view your custom counters is with the Performance Monitor (PerfMon) tool. You can add your counters to graphs, reports, or alerts.

Advanced Tips for Power Users

• Multi-Instance Counters: Track metrics for multiple instances of a component (e.g., each thread).
• Remote Monitoring: Monitor performance on remote machines.
• Custom Data Formats: Display your counter values in a way that makes sense for your application.

Ready to Supercharge Your C/C++ Applications?

Custom performance counters are a powerful tool for understanding and optimizing your code. By following this guide, you’ll gain the knowledge and skills to track the metrics that matter most and take your applications to the next level.

Dialog boxes are essential components of user interfaces, serving as windows for communication between the user and your application. In the realm of C programming, you’ll encounter two distinct types of dialogs: modal and modeless. Each type has a unique purpose and understanding their differences is crucial for crafting effective user experiences. Let’s delve into the world of dialogs and explore how to implement them in your C applications.

What are Modal Dialogs?

Modal dialogs are windows that demand your attention. They halt the main application’s execution, requiring you to interact with them before you can proceed. These dialogs are often used for critical tasks like:

• Alerts: Displaying error messages or warnings that require immediate attention.
• Confirmations: Prompting you to confirm an action before it’s executed.
• Input Forms: Gathering essential information from you.

In C, modal dialogs can be created using various libraries or APIs, such as Win32 API for Windows applications. Here’s a simplified example of how to create a modal dialog:

// ... (Win32 API includes and setup)

DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), hWndParent, DialogProc); 

// ... (DialogProc function definition)

What are Modeless Dialogs?

In contrast to modal dialogs, modeless dialogs are independent windows that coexist with the main application. They don’t block execution, allowing you to interact with both the dialog and the main window simultaneously. Modeless dialogs are often used for:

• Tools: Providing additional functionality or options.
• Information Displays: Showing progress indicators or status updates.
• Secondary Input: Offering supplementary input options alongside the main task.

Creating a modeless dialog in C is similar to creating a modal one, but you’ll use a different function like CreateDialog:

// ... (Win32 API includes and setup)

HWND hDlg = CreateDialog(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), hWndParent, DialogProc);
ShowWindow(hDlg, SW_SHOW);

// ... (DialogProc function definition)

Key Differences and Use Cases

Modal dialogs are ideal for situations where a user’s response is essential before proceeding, such as error notifications or confirmation prompts.

Modeless dialogs are better suited for providing supplemental information or tools that can be accessed while the main application remains active.

Implementing Dialogs in C

The specific implementation of modal and modeless dialogs will vary depending on your development environment and target platform. Libraries like Win32 API, GTK+, or Qt offer robust tools for creating dialogs with custom layouts, controls, and event handling.

Best Practices and Considerations

• Keep it concise: Dialogs should be focused and avoid overwhelming the user with excessive information or controls.
• Use clear labels: Ensure all controls and buttons are appropriately labeled to guide the user.
• Provide feedback: Use visual cues or messages to acknowledge user actions within the dialog.
• Accessibility: Design dialogs with accessibility in mind, ensuring they can be used by individuals with disabilities.

Conclusion

Understanding the distinction between modal and modeless dialogs is fundamental for creating user-friendly interfaces in your C applications. By strategically employing these dialog types, you can effectively communicate with users, gather input, and enhance the overall experience of your software.

Remember, the key is to choose the right type of dialog for the right task. Consider the nature of the information you need to convey or the action you want the user to take. With careful planning and implementation, dialog boxes can become powerful tools in your C programming toolkit.

In the world of web development, ASP.NET’s ViewState mechanism is a key player in maintaining the state of your web page across postbacks. Ever wondered how your page remembers the values you entered in textboxes or the selected item in a dropdown list after you click a button? ViewState is the answer.

Understanding Postbacks

Web pages are stateless by nature. Each time you interact with a page (e.g., click a button), the server processes your request, generates a new HTML response, and sends it back to the browser. This process is called a postback. Without a mechanism like ViewState, the page would lose all the information you entered or selected during the previous interaction.

Enter ViewState

ViewState is ASP.NET’s way of preserving page and control values between round trips to the server. It works like this:

1. Serialization: Before rendering the page, ASP.NET serializes the current state of the page and its controls into a base64-encoded string.
2. Hidden Field: This serialized string is stored in a hidden form field called __VIEWSTATE.
3. Postback: When the user submits the form (via a button click or other action), the __VIEWSTATE field is sent back to the server along with the rest of the form data.
4. Deserialization: The server deserializes the __VIEWSTATE string, restoring the page and control values to their previous state.

Benefits of ViewState

• Preserves UI State: Maintains values in textboxes, selections in dropdowns, and other control states.
• Automatic: Works automatically for most ASP.NET controls without explicit code.
• Simple to Use: No complex coding required to enable basic ViewState functionality.

Drawbacks of ViewState

• Increased Page Size: The serialized ViewState data can add significant size to your page, potentially slowing down page load times.
• Security Concerns: While the data is encoded, it’s not encrypted. Avoid storing sensitive information in ViewState.
• Limited Control: The default ViewState mechanism might not be ideal for all scenarios.

Controlling ViewState

• Enable/Disable: You can disable ViewState for a page or specific controls if you don’t need it.
• ViewStateMode: Use the ViewStateMode property to control whether ViewState is enabled at the page, control, or child control level.
• Custom ViewState Provider: For advanced scenarios, create your own custom ViewState provider to store ViewState data in a different location (e.g., Session, database).

Best Practices

• Minimize ViewState Size: Store only essential data in ViewState.
• Use Alternatives: Consider using Session state, hidden fields, or control state for specific scenarios where ViewState isn’t the best fit.
• Security: Never store sensitive information in plain text in ViewState.

The Label control (<asp:Label>) is a fundamental building block in ASP.NET web pages. Its primary purpose is to display text or data on your page, but it offers much more than that. Here’s what you need to know:

Key Features

• Text Display: The most obvious use case is to display static text or dynamic content.
• Data Binding: You can easily bind a Label to a data source (database, XML file, etc.) to display data from a specific field or property.
• Formatting: Customize the appearance of the text using CSS classes or inline styles (font, color, size, etc.).
• Dynamic Updates: Programmatically change the text of the Label in response to user interactions or events.

Typical Lab 004 Tasks

Based on the common structure of introductory ASP.NET labs, here’s what you might expect in Lab 004:

1. Basic Text Display:
   • Create a Label control on your web page and set its Text property to display some initial text.

Code snippet

<asp:Label ID=”MyLabel” runat=”server” Text=”Hello, World!” />

1. Dynamic Text Update:
   • Write code in your code-behind file (C# or VB.NET) to change the Text property of the Label based on a button click or other event.

C#

protected void Button1_Click(object sender, EventArgs e)

{

    MyLabel.Text = “Button clicked!”;

}

1. Data Binding:
   • Connect the Label to a data source (e.g., a SqlDataSource control) and display data from a specific field.

Code snippet

<asp:Label ID=”NameLabel” runat=”server” Text='<%# Eval(“Name”) %>’ />

1. Conditional Formatting:
   • Use code to change the style of the Label based on a condition (e.g., make the text red if a value is negative).

C#

if (value < 0)

{

    MyLabel.ForeColor = System.Drawing.Color.Red;

}

Advanced Tasks (Optional)

• Templates: Use templates (ItemTemplate, AlternatingItemTemplate, etc.) to customize the appearance of Labels within data-bound controls like GridView or Repeater.
• Localization: Apply localization techniques to display the Label’s text in different languages.

Example: Greeting Message with Time

Code snippet

<asp:Label ID=”GreetingLabel” runat=”server”></asp:Label>

C#

protected void Page_Load(object sender, EventArgs e)

{

    int hour = DateTime.Now.Hour;

    if (hour < 12)

    {

        GreetingLabel.Text = “Good morning!”;

    }

    else if (hour < 18)

    {

        GreetingLabel.Text = “Good afternoon!”;

    }

    else

    {

        GreetingLabel.Text = “Good evening!”;

    }

}

Tips

• Explore Properties: The Label control has many properties (ForeColor, Font, etc.). Experiment with them to customize the appearance.
• Event Handling: Use events like DataBinding to modify the text or style of the Label during data binding.

ASP.NET web pages follow a well-defined life cycle, consisting of several events that occur during a page’s request and rendering process. Understanding these events is crucial for building dynamic and interactive web applications. Here’s a simplified overview of the key page events:

1. PreInit:
   • The earliest event in the page life cycle.
   • Ideal for setting master pages, themes, and dynamic controls.
2. Init:
   • Controls on the page are initialized and their default values are set.
3. InitComplete:
   • Raised after all controls have been initialized.
4. PreLoad:
   • Occurs before the page starts loading view state and postback data.
5. Load:
   • View state and control state are loaded.
   • Controls are populated with data.
   • This is where you typically perform tasks like data binding.
6. LoadComplete:
   • Page loading is complete, and all controls have been fully loaded.
7. PreRender:
   • The last chance to make changes to the page or its controls before they are rendered.
8. SaveStateComplete:
   • View state and control state are saved.
9. Render:
   • The page and its controls are rendered into HTML to be sent to the browser.
10. Unload:
    • The page is unloaded from memory.
    • Perform cleanup tasks here (closing database connections, etc.).

Typical Lab 003 Tasks

Based on the common structure of introductory ASP.NET labs, here’s what you might expect in Lab 003:

• Event Handling: You’ll likely write code to handle various page events (e.g., Page_Load, Button_Click). This involves writing event handler methods in your code-behind file (.aspx.cs or .aspx.vb).
• Event Order Demonstration: The lab might ask you to track the order in which events are fired. You can do this by adding logging statements (e.g., using Response.Write or a logging library) within each event handler.
• Dynamic Content Generation: You might be asked to modify the page’s content dynamically during different events (e.g., changing label text, adding controls).
• State Management: Explore how to maintain state between postbacks using ViewState or Session variables.

Example: Tracking Page Events

C#

protected void Page_PreInit(object sender, EventArgs e)

{

    Response.Write(“PreInit event fired.<br>”);

}

protected void Page_Load(object sender, EventArgs e)

{

    Response.Write(“Load event fired.<br>”);

}

// … (similar handlers for other events)

Tips:

• Breakpoints: Use breakpoints in your code-behind to pause execution and inspect the state of your page at different points in the life cycle.
• Debugging: Utilize the debugger to step through your code and observe the sequence of events.
• Refer to Resources: Consult your course materials, textbooks, or online resources for more detailed information on ASP.NET page events.

In the world of web development, connecting to a database and retrieving or manipulating data is a fundamental task. ASP.NET Web Pages, with their Razor syntax, provide a streamlined way to achieve this using SqlCommand and SqlDataReader. Let’s dive into how to leverage these powerful tools.

Setting the Stage: Database Connection

First, make sure you have a valid connection string for your database. This string typically includes information about the database server, the database name, and credentials. Store this connection string securely, either in your web.config file or in a separate configuration file.

C#

var connectionString = “Your_Connection_String_Here”; // Replace with your actual connection string

Crafting Your SQL Command

Next, create a SqlCommand object. This object encapsulates your SQL query or stored procedure and the database connection.

C#

using (var connection = new SqlConnection(connectionString))

{

    connection.Open();

    var command = new SqlCommand(“SELECT * FROM Products”, connection); // Example query

    // Execute the command and process the results (see below)

}

Fetching Data with SqlDataReader

To retrieve data from the database, use the ExecuteReader method of the SqlCommand object. This returns a SqlDataReader that you can use to read the results row by row.

C#

using (var reader = command.ExecuteReader())

{

    while (reader.Read())

    {

        // Process each row of data here

        var productName = reader[“ProductName”].ToString();

        var unitPrice = (decimal)reader[“UnitPrice”];

        // … (access other columns as needed)

    }

}

Important Considerations:

• Using Blocks: Always wrap your database interactions within using blocks. This ensures that the connection and other resources are properly disposed of, even if an exception occurs.
• Parameterization: For security and performance, use parameterized queries to avoid SQL injection attacks and optimize query execution plans.

Example: Displaying Products in a Table

HTML

@{

    var connectionString = “Your_Connection_String_Here”;

    using (var connection = new SqlConnection(connectionString))

    {

        connection.Open();

        var command = new SqlCommand(“SELECT ProductName, UnitPrice FROM Products”, connection);

        <table>

            <tr>

                <th>Product Name</th>

                <th>Unit Price</th>

            </tr>

            using (var reader = command.ExecuteReader())

            {

                while (reader.Read())

                {

                    <tr>

                        <td>@reader[“ProductName”]</td>

                        <td>@reader[“UnitPrice”]</td>

                    </tr>

                }

            }

        </table>

    }

}

Key Takeaways:

• SqlCommand allows you to execute SQL queries and stored procedures.
• SqlDataReader provides an efficient way to read the results of a query row by row.
• Always use parameterized queries to protect against SQL injection.
• Dispose of connections and resources properly using using blocks.

The MultiView control in ASP.NET is a powerful tool for creating user interfaces with multiple views or sections. It allows you to display different content or layouts within a single container, making it ideal for scenarios like wizards, tabbed interfaces, or dynamic content switching.

Key Concepts

1. Views (<asp:View>):
   • Each view represents a distinct section of content within the MultiView.
   • Views can contain any ASP.NET controls (labels, textboxes, buttons, etc.).
   • Only one view is visible at a time.
2. ActiveViewIndex:
   • An integer property of the MultiView that determines which view is currently active and visible.

Working with MultiView and Views

• Adding Views: You can add views to a MultiView control either declaratively in your ASPX markup or programmatically in your code-behind.
• Switching Views: Change the ActiveViewIndex property to switch between views. This can be done in response to user interactions (button clicks, etc.) or based on other conditions.
• Accessing View Controls: You can access and manipulate controls within a specific view by referencing the view object and its child controls.

Common Lab Tasks

Here are some tasks you might encounter in a lab like Lab 014:

• • Creating a Wizard:Use a MultiView with multiple views to guide the user through a step-by-step process.
  • Implementing Tabbed Navigation:Create a set of buttons or links that switch between views to simulate tabs.
  • Dynamically Generating Views:Programmatically create and add views to the MultiView based on data or user preferences.
  • Validating Input Across Views:Ensure that user input is valid before switching to the next view in a wizard-like scenario.
  • Persisting State Across Views:Use techniques like ViewState or Session to maintain data between views as the user interacts with the MultiView.

Example: Simple Tabbed Interface

Code snippet

<asp:MultiView ID=”MultiView1″ runat=”server” ActiveViewIndex=”0″>

    <asp:View ID=”View1″ runat=”server”>

        <h2>View 1</h2>

        <p>This is the content of View 1.</p>

    </asp:View>

    <asp:View ID=”View2″ runat=”server”>

        <h2>View 2</h2>

        <p>This is the content of View 2.</p>

    </asp:View>

</asp:MultiView>

<asp:Button ID=”Button1″ runat=”server” Text=”Go to View 1″ OnClick=”Button1_Click” />

<asp:Button ID=”Button2″ runat=”server” Text=”Go to View 2″ OnClick=”Button2_Click” />

C#

protected void Button1_Click(object sender, EventArgs e)

{

    MultiView1.ActiveViewIndex = 0;

}

protected void Button2_Click(object sender, EventArgs e)

{

    MultiView1.ActiveViewIndex = 1;

}