Best Practices for Web Services: Choosing the Right Instantiation Method

When developing applications that use web services, one of the key considerations is how to manage the service’s lifecycle efficiently. A developer recently posed a question regarding the best practice for instantiating a web service in their application. Should it be instantiated with every method call, or should it persist throughout the application? In this blog post, we’ll explore these strategies and provide detailed insights into the best practices for managing web services.

The Dilemma: Instantiation Methods

Method 1: Instant Creation Per Call

The first approach is to instantiate the web service each time a method is called. This strategy involves creating a new service instance within the event handler, using it, and then disposing of it immediately after the method call:

private void btnRead_Click(object sender, EventArgs e)
{
    try
    {
        //Show clock
        this.picResult.Image = new Bitmap(pathWait);
        Application.DoEvents();

        //Connect to webservice
        svc = new ForPocketPC.ServiceForPocketPC();
        // Configuration parameters here...
        svc.CallMethod();
        // Further processing...
    }
    catch (Exception ex)
    {
        ShowError(ex);
    }
    finally
    {
        if (svc != null)
            svc.Dispose();
    }
}

Pros:

• Reduces the amount of memory consumed by keeping only necessary instances.
• Ensures a fresh connection each time, which can be beneficial if the service or network experiences intermittent issues.

Cons:

• Higher overhead in terms of performance due to repeated instantiation and disposal operations.
• Slower responses as each request initializes a new connection.

Method 2: Persistent Instance

The second strategy involves creating a web service instance when the application loads and keeping it available for the lifetime of the application or form:

private myWebservice svc;

private void Main_Load(object sender, EventArgs e)
{
    // Connect to webservice
    svc = new ForPocketPC.ServiceForPocketPC();
    // Configuration parameters here...
}

private void btnRead_Click(object sender, EventArgs e)
{
    try
    {
        //Show clock
        this.picResult.Image = new Bitmap(pathWait);
        Application.DoEvents();
        svc.CallMethod();
        // Further processing...
    }
    catch (Exception ex)
    {
        ShowError(ex);
    }
}

private void Main_Closing(object sender, CancelEventArgs e)
{
    svc.Dispose();
}

Pros:

• Improved performance due to reduced overhead; the service is only instantiated once.
• Better management of the persistent state when dealing with services that require session data.

Cons:

• Keeps a connection open for the application’s lifespan, using more resources.
• If the service becomes unresponsive, it might affect all operations that rely on it.

Which to Choose?

The decision between these two strategies depends largely on the specific needs and behavior of your application:

1. Frequency of Calls:

   • If you plan to call the web service frequently (e.g., multiple times per user interaction), then Method 2 is preferable. It minimizes the instantiation overhead and speeds up response times.
   • If the web service will only be used sporadically, consider Method 1 to avoid unnecessary resource consumption.

2. Resource Management:

   • Analyze the server capabilities and limits. If the server can handle many concurrent connections effectively, then a persistent instance may be advantageous.
   • For resource-limited environments or services that are likely to become stale, instantiating per call is optimal.

3. Error Handling:

   • With a long-lived service, be prepared to handle potential errors when the service becomes unresponsive. Implement retries or fallbacks in your method calls.

Conclusion

Understanding how to manage the lifecycle of your web services is crucial for building efficient applications. Each method has its benefits and drawbacks that must be weighed against your application’s requirements. By considering your call frequency, resource management capabilities, and error handling strategies, you can select the best practice that aligns with your project’s goals.

In any case, keeping your code clean, well-documented, and adaptable will serve you well as your application evolves. Happy coding!