---
title: Listen for trace events
slug: cms-12/docs/tracing-events
docTags: 
createdAt: 2026-08-10T15:55:57.000Z
---

To receive events raised from the tracing API, you are required to register a listener by implementing the `ITraceListener` interface. The initialization code in Optimizely Search & Navigation searches assemblies located in the current app domain and registers the implementations, if any, that exist.

Below is an example of a trace events listener which sends an email in case of an error.

```csharp
using System.Collections.Generic;
using EPiServer.Find.Tracing;
public class TestTraceListener: ITraceListener {
  public TestTraceListener() {}
  public virtual void Add(ITraceEvent traceEvent) {
    if (traceEvent.IsError) {
      MailAdmin(traceEvent.Exception, traceEvent.Message)
    }
  }
}
```

The interface of `ITraceEvent` looks like this:

```csharp
public interface ITraceEvent {
  DateTime Timestamp {
    get;
  }
  ITraceable Source {
    get;
  }
  string Message {
    get;
  }
  bool IsError {
    get;
  }
  Exception Exception {
    get;
    set;
  }
}
```

## Example – Network issues when connecting to the index

You can use tracing to generate notifications of service exceptions. To do so, handle the following exceptions like this:

```csharp
public class TestTraceListener: ITraceListener {
  public virtual void Add(ITraceEvent traceEvent) {
    if (traceEvent.IsError && traceEvent.Exception is typeof (ServiceException)) {
      // inspect Response code to determine course of action
      AlertOperations(traceEvent.Exception, traceEvent.Message, "Find Index potentially down.")
    }
  }
}
```

## Example – Document storage limit reached

This example generates a notification when the number of indexed items reaches the limit configured in your Optimizely Search & Navigation service subscription.

```csharp
public class TestTraceListener: ITraceListener {
  public virtual void Add(ITraceEvent traceEvent) {
    if (traceEvent.IsError && traceEvent.Exception is typeof (ServiceException)) {
      // if response code is 403 and message contains "Your account is not authorized to index more than"
      AlertAccountMgr(traceEvent.Exception, traceEvent.Message, "limit reached for Find License")
    }
  }
}
```