# IT:AD:Elmah:HowTo #



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* [[../|(UP)]]
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* See also:
    * [[IT/AD/SCOM/]]
    * [[IT/AD/Event Log/]]


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<panel title="Summary">

**E**rror **L**ogging **M**odules **A**nd **H**andlers (ELMAH).

* ELMAH doesn't change the error experience (still see "Server Error", etc.)
* ELMAH behind the scenes uses a [[IT/AD/NET/Web/HttpModule/]] to trap unhandled exceptions:


<sxh csharp>
protected virtual void OnError(object sender, EventArgs args) {
  var app = (HttpApplication)sender); Log(app.Server.GetLastError(), app.Context);
}
</sxh>


* Makes it available to be seen as a webpage (`/corp.com/site/elmah.axh`)

![](https://dl.dropboxusercontent.com/u/11851202/Posted/IT/About/Elmah/report.gif)

* Comprised of:
   * An HTTP module subsystem
       * records the messsages to an error logging subsystem
   * An HTTP handler subsystem
       * retrieves messages from the error logging subsystem


</panel>


## ACiD

* Advantages:
    * Surfaces errors to a webpage, so that you don't need to crack open the Event Log Viewer.
* Considerations:
    * You have configure it to limit it to authorized people.
    * **Important:** WCF exception are intercepted by ASP.NET and a SOAP fault is returned to the client. ie, Elmah won't get them. To log them, you need a SOAP Extension.
* Disadvantages:
    * Yet another thing to learn about, in order to configure via the web.config file beyond the website proper...


## Resources ##
*https://msdn.microsoft.com/en-us/library/aa479332.aspx
* https://code.google.com/p/elmah/