On my previous posts on this health monitoring series I explain to you how and why I made my own EventLogWebEventProvider and which benefits you can achieve by using this provider or by making your own.

Now I'll write about how to use this new provider in one application.

Well, almost everything have been written about this topic and Microsoft has one good article on "How To: Use Health Monitoring in ASP.NET 2.0" so I wont even try to explain all the possible scenarios and configurations, I will simply explain the standard scenario.

Typically I simply want to keep track on two Web Event types:

1. the ones related to application errors
2. an the others related to application life cycle

As far as I notice there are many people that simply track those from point 1.

Another decision to make is where to store these Web Events data, You do this by choosing a Web Event provider.

ASP.NET give us out-of-the-box several providers and you can make your own provider. Once your provider is done you can use it just like all the others.

In this example I will use the newly created provider.

Now that I know exactly what to track and where to store it I can update my configuration.

All health monitoring configuration data is stored in the system.web\healthMonitoring section and my standard configuration will look like:

<healthMonitoring enabled="true">
  <providers>
    <add name="ExtendedEventLogWebEventProvider" type="NG.Web.Management.EventLogWebEventProvider, NG.Web" source="MyEvtLogSource" />
  </providers>
  <rules>
    <clear />
    <add name="Application Lifetime Events Default" eventName="Application Lifetime Events" provider="ExtendedEventLogWebEventProvider" profile="Default" />
    <add name="All Errors Default" eventName="All Errors" provider="ExtendedEventLogWebEventProvider" profile="Default" />
  </rules>
</healthMonitoring>

Notice the source attribute from the ExtendedEventLogWebEventProvider, using it you can set which EventLog source to use.

Remember that when you create a EventLog source you can choose to create a brand new EventLog and if you choose so, all entries written by this provider in this application context will be isolated from all the others providing one easy way for visual tracking and filtering.

With the health monitoring data in place you should now be able to see the entries appearing in EventLog.

In the first post of this series I've manage to find the correct eventId for each Web Event type, and by this time the major problem has been solved, but I cannot yet write a correct entry into the EventLog.

I still have to decided the best severity type and category to apply.

Severity

If you look at entries in the EventLog generated by the default EventLogWebEventProvider you will find that they are marked mainly as Information and a few of them are also marked as Warning but no one is ever marked as Error.

Since I'm making my own provider I will take this chance to map the EventLog entry severity type according to the source Web Event.More...

The ASP.NET health monitoring enables you to add instrumentation to Web applications by using the so called Web Events. These Web events give us information about health status.

You can configure health monitoring by setting events and providers in the healthMonitoring section.

Naturally, ASP.NET provide us with a few out-of-the-box providers such as the EventLogWebEventProvider.

As many of you may have already notice, when using the EventLogWebEventProvider the events are added to the Application EventLog with the following source pattern:

        ASP.NET "framework version"

If you are using ASP.NET 2.0 the source will look similar to "ASP.NET 2.0.50727.0 ".

You can imagine what happen when a server hosts several web applications ... you can't easily figure which application raised a web event because you can't apply a filter to do that. To figure it out you must inspect the eventlog entry data.

If you think this is wrong and that Microsoft should do something about it, go here and here, vote and comment.

What can you do to overlap this? Well you can create your own EventLogWebEventProvider that allows you to specified which Source to use.

Doing such a provider is fairly simple but lead us to THE problem: which eventId to use when creating the EventLog entry?

What? Why is this a problem? are you saying.

Well, lets start all from the beginning ... you want to create your own provider so you can specify the EventLog source but you certainly desire to keep the remaining settings unchanged so that monitoring applications that track the EventLog entry for well known eventIds still working fine.

The problem is that Microsoft don't expose the algorithm used to created the eventId from the WebEvent data, and this way we can only guess which eventId to use.

If you look at EventLogWebEventProvider.ProcessEvent method you will find the following code:

int num = UnsafeNativeMethods.RaiseEventlogEvent((int) type, (string[]) dataFields.ToArray(typeof(string)), dataFields.Count); 

This is your black box, no source or information is available.

To guess which eventId is used for a specific Web Event I created a small page that raises all known Web  Events.

I found that even with all known Web Events configured to use EventLogWebEventProvider almost half of them don't appear in EventLog, but those that have an EventLog entry made me speculate that eventIds are sequential and follow the classes hierarchy. Here are the results:

Please note that I'm considering that no two different Web Events share the same eventId.

If you believe the assumptions made are correct you can now start coding your provider.

Remember that you must create the EventLog source before  use it. You can do this by using the EventLog.CreateEventSource method.

Recently, while digging on ASP.NET 2.0 Health Monitoring I found a bug in the EventMappingSettingsCollection.Contains class method.

I was trying to check if an event mapping already exists but every time I try it the following exception was thrown:

System.NullReferenceException was unhandled by user code
  Message="Object reference not set to an instance of an object."
  Source="System.Web"
  StackTrace:
       at System.Web.Configuration.EventMappingSettingsCollection.GetElementKey(ConfigurationElement element)
       at System.Configuration.ConfigurationElementCollection.GetElementKeyInternal(ConfigurationElement element)
       at System.Configuration.ConfigurationElementCollection.BaseIndexOf(ConfigurationElement element)
       at System.Web.Configuration.EventMappingSettingsCollection.IndexOf(String name)
       at System.Web.Configuration.EventMappingSettingsCollection.Contains(String name)

I opened a bug in connect, so, if you think this is important go there and vote.

And if you think this one is not a common error ... well ... this is the second bug I found regarding Contains method from a collection class.

A few weeks ago I told you about a control toolkit I was making.

I decided to call him NunoGomesControlToolkit and is intended to improve web apps performance by decreasing total page size. This page size reduction is achieved by decreasing control ClientID size.

This control toolkit can be applied to any existing ASP.NET 2.0 Web Aplication by using the tagmapping configuration facility.

To obtain maximum redution it's also recommended to extend webforms, masterpages and usercontrols not from regular Page, MasterPage and UserControl controls from ASP.NET framework but instead use the corresponding control from NunoGomesControlToolkit.

TagMapping is only used for markup interpretation and therefore all dynamic created controls are not mapped. To override this limitation its also included in this toolkit the DynamicControlBuilder class. Use this class to allow tagmapping over dynamic created controls.

As I promise, the control toolkit is now available at code.msdn.microsoft.com.

I'm currently applying the NunoGomesControlToolkit to the BlogEngine.NET 1.3 version, and as soon as I test it I will make it available.

In the previous posts on this subject I wrote about why automatic ID generation should be improved and how we can improve it. Now I will step forward and show you my own implementation of a specific naming provider.

As we saw in part 3, to create a specific Naming provider you only need to develop your own implementation of SetControlID method.

I named my naming provider ShortIDsProvider and it will have only one specification to meet:

• it will create IDs in the form Txxx

where T denotes the 'T' character and xxx denotes an unique incremental integer value.More...

Naming container controls are a subclass of standard controls, that differ in the ability to manage child controls' ID, in fact, these naming container controls are the key to unique ID generation. To become a namingcontainer a regular control must implement the INamingContainer interface.

In order to override ASP.NET ID generation we will have to work in two fronts:

• override regular controls' behavior to decouple the Control.UniqueID property from the Control.ID property
• override naming container controls to allow us to control how ID generation is done and how to find a control 

More...

I already posted here about Tag Mapping and how helpful it can be, but naturally there's are a few improvements that I would like to see available in future framework release.

The one I expect the most is about the capability of mapping dynamic created controls using the same rules as Tag Mapping uses when interpreting the page markup.

Without this capability we can never use widely the tag mapping because whenever we need to create dynamic controls they will be strongly coupled to a specific control implementation.

Imagine this scenario:

1. First you have built an web application that use standard ASP.NET TextBox  control, some of them dynamically created.
2. Now, imagine that you want to reuse that application, as is, but instead of ASP.NET Textbox control you want to use your own Textbox implementation.

This task could be easily accomplished using Tag Mapping if no dynamic controls were used, but in this scenario ASP.NET give us no solution, so the application cannot be reused without modifications.

Naturally, you can copy/paste your application and make the necessary changes, or even add a few if statements, but that will only increase complexity and maintenance effort.

Until the .NET team provide us such capability we must do the magic ourselves.

My proposal is an help class (DynamicControlBuilder) that provide us two methods: GetMappedType and CreateControl.

/// <summary>
/// Gets the mapped <see cref="System.Web.UI.Control"/> type.
/// </summary>
/// <param name="type">The <see cref="System.Web.UI.Control"/> type to be mapped</param>
/// <param name="prefix">The namespace prefix.</param>
/// <returns>A <see cref="System.Type"/> object.</returns>
public static Type GetMappedType(Type type, string prefix)
{
    if (!typeof(Control).IsAssignableFrom(type))
    {
        throw new ArgumentOutOfRangeException("type", "Must inherit from Control.");
    }
    Type mappedtype;
    if (!string.IsNullOrEmpty(prefix))
    {
        TagPrefixInfo prefixinfo;
        if (!m_prefixes.TryGetValue(prefix, out prefixinfo))
        {
            throw new ArgumentException("prefix", "No prefix found.");
        }
        else
        {
            type = BuildManager.GetType(string.Format("{0}.{1}, {2}", prefixinfo.Namespace, type.UnderlyingSystemType.Name, prefixinfo.Assembly), false);
            if (type == null)
            {
                throw new ArgumentException("type", "Control not found within specified prefix.");
            }
        }
    }
    if (m_tagMappings.TryGetValue(type.UnderlyingSystemType, out mappedtype))
    {
        return mappedtype;
    }
    return type;
}

/// <summary>
/// Creates a dynamic mapped <see cref="System.Web.UI.Control"/>.
/// </summary>
/// <param name="type">The <see cref="System.Web.UI.Control"/> type to be mapped</param>
/// <param name="prefix">The namespace prefix.</param>
/// <returns>A <paramref name="T"/> object.</returns>
public static Control CreateControl(Type type, string prefix)
{
    Type mappedType = GetMappedType(type, prefix); ;
    return (Control)Activator.CreateInstance(mappedType);
}

The main goal is to enable any of the following usages:

this.Page.Controls.Add(DynamicControlBuilder.CreateControl<System.Web.UI.WebControls.TextBox>("foo"));

this.Page.Controls.Add(DynamicControlBuilder.CreateControl(typeof(System.Web.UI.WebControls.TextBox), "foo"));

this.Page.Controls.Add(DynamicControlBuilder.CreateControl(typeof(System.Web.UI.WebControls.TextBox)));

Try it !

DynamicControlBuilder.cs (7.13 kb)