IntelliTrace for Visual Studio Enterprise (C#, Visual Basic, C++)
Applies to: 
Visual Studio 
Visual Studio for Mac
Note
This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here
You can spend less time debugging your application when you use IntelliTrace to record and trace your code's execution history. You can find bugs easily because IntelliTrace lets you:
Record specific events
Examine related code, data that appears in the Locals window during debugger events, and function call information
Debug errors that are hard to reproduce or that happen in deployment
You can use IntelliTrace in Visual Studio Enterprise edition (but not the Professional or Community editions).
What do you want to do?
| Scenario | Title |
|---|---|
| Debug my application with IntelliTrace: - Show me past events. - Show me call information with past events. - Save my IntelliTrace session. - Control the data that IntelliTrace collects. |
- Inspect previous app states using IntelliTrace - Walkthrough: Using IntelliTrace - IntelliTrace Features - Historical Debugging |
| Collect IntelliTrace data from deployed applications | - Using the IntelliTrace stand-alone collector |
| Start debugging from an IntelliTrace log file (.iTrace file). | - Using saved IntelliTrace data |
What apps can I debug with IntelliTrace?
| Support level | Application types |
|---|---|
| Full support | - Visual Basic and Visual C# applications that use .NET Framework 2.0 or higher versions. You can debug most applications, including ASP.NET, Microsoft Azure, Windows Forms, WCF, WPF, Windows Workflow, SharePoint 2010, SharePoint 2013, and 64-bit apps. To debug SharePoint applications with IntelliTrace, see Walkthrough: Debugging a SharePoint Application by Using IntelliTrace. To debug Microsoft Azure apps with IntelliTrace, see Debugging a Published Cloud Service with IntelliTrace and Visual Studio. |
| Limited support | - C++ apps targeting Windows support viewing snapshots using IntelliTrace step-back. Only debugger and exception events are supported. - .NET Core and ASP.NET Core apps supported for certain events only (MVC Controller, ADO.NET, and HTTPClient events) in local debugging. The Standalone Collector is not supported for .NET Core or ASP.NET Core apps. - F# apps on an experimental basis - UWP apps supported for events only |
| Not supported | - Other languages and script - Windows Services, Silverlight, Xbox, or Windows Mobile apps |
Note
If you want to debug a process that is already running, you can collect IntelliTrace events only (no call information). You can attach to a 32-bit or 64-bit process on the local machine only. Events that occur before you attach to the process are not collected.
Why debug with IntelliTrace?
Traditional or live debugging shows only your application's current state, with limited data about past events. You either have to infer these events based on the application's current state, or you have to recreate these events by rerunning your application.
IntelliTrace expands this traditional debugging experience by recording specific events and data at these points in time. This lets you see what happened in your application without restarting it, especially if you step past where the bug is. IntelliTrace is turned on by default during traditional debugging and collects data automatically and invisibly. This lets you switch easily between traditional debugging and IntelliTrace debugging to see the recorded information. See IntelliTrace Features and What data does IntelliTrace collect?
IntelliTrace can also help you debug errors that are hard to reproduce or that happen in deployment. You can collect IntelliTrace data and save it to an IntelliTrace log file (.iTrace file). An .iTrace file contains details about exceptions, performance events, Web requests, test data, threads, modules, and other system information. You can open this file in Visual Studio Enterprise, select an item, and start debugging with IntelliTrace. This lets you go to any event in the file and see specific details about your application at that point in time.
You can save IntelliTrace data from these sources:
An IntelliTrace session in Visual Studio 2015 Enterprise or later versions, or previous versions of Visual Studio Ultimate.
ASP.NET web apps hosted on IIS, or SharePoint 2010 and SharePoint 2013 applications running in deployment when you use Microsoft Monitoring Agent, either alone or with System Center 2012. See Use the IntelliTrace stand-alone collector and Monitoring with Microsoft Monitoring Agent.
Here are some examples of how IntelliTrace can help you with debugging:
Your application has corrupted a data file, but you don't know where this event happened.
Without IntelliTrace, you have to look through the code to find all possible file accesses, put breakpoints on those accesses, and rerun your application to find where the problem happened. With IntelliTrace, you can see all the collected file-access events and specific details about your application when each event happened.
An exception happens.
Without IntelliTrace, you get a message about an exception but you don't have much information about the events that led to the exception. You can examine the call stack to see the chain of calls that led to the exception, but you can't see the sequence of events that happened during those calls. With IntelliTrace, you can examine the events that happened before the exception.
A bug or crash happens in a deployed application.
For Microsoft Azure-based apps, you can configure IntelliTrace data collection before you publish the application. While your application runs, IntelliTrace saves data to an .iTrace file. See Debug a Published Cloud Service with IntelliTrace and Visual Studio.
For ASP.NET web apps hosted on IIS 7.0, 7.5, and 8.0, and SharePoint 2010 or SharePoint 2013 applications, use Microsoft Monitoring Agent, either alone or with System Center 2012, to save IntelliTrace data to an .iTrace file.
This is useful when you want to diagnose problems with apps in deployment. See Use the IntelliTrace stand-alone collector.
What data does IntelliTrace collect?
Collect event information
By default, IntelliTrace records only IntelliTrace events: debugger events, exceptions, .NET Framework events, and other system events that can help you with debugging. You can choose the kinds of IntelliTrace events that you want to collect, except for debugger events and exceptions, which are always collected. See IntelliTrace features.
Debugger events
IntelliTrace always records events that happen in the Visual Studio debugger. For example, starting your application is a debugger event. Other debugger events are stopping events, which cause your application to break execution. For example, your program hits a breakpoint, hits a tracepoint, or executes a Step command.
By default, to help with performance, IntelliTrace doesn't record every possible value for a debugger event. Instead, it records these values:
Values in the Locals window. Keep the Locals window open to see these values.
Values in the Autos window only if the Autos window is open
Values in DataTips that appear when you move the mouse pointer on top of a variable in the source window to see its value. IntelliTrace doesn't collect values in pinned DataTips.
When IntelliTrace Events and Snapshots mode is enabled, IntelliTrace will take a snapshot of the application's process at each debugger Breakpoint and Step event. This will record values in the Locals, Autos, and Watch windows, regardless of whether the windows are open or not. Values in any pinned data tips will also be collected.
Exceptions
IntelliTrace records the exception type and message for these kinds of exceptions:
Handled exceptions where the exception is thrown and caught
Unhandled exceptions
.NET Framework events
By default, IntelliTrace records the most common .NET Framework events. For example, for a CheckBox.CheckedChanged event, IntelliTrace collects the checkbox state and text.
SharePoint 2010 and SharePoint 2013 application events
You can record user profile events and a subset of Unified Logging System (ULS) events for SharePoint 2010 and 2013 applications running outside Visual Studio. You can save these events to an .iTrace file. Requires Visual Studio Enterprise 2015 or later versions, a previous version of Visual Studio Ultimate, or Microsoft Monitoring Agent running in Trace mode.
When you open the .iTrace file, enter a SharePoint correlation ID to find its matching web request, view the recorded events, and start debugging from a specific event. If the file contains unhandled exceptions, you can choose a correlation ID to start debugging an exception.
See:
Capture snapshots
You can configure IntelliTrace to capture snapshots at every breakpoint and debugger step event. IntelliTrace records the full application state at each snapshot, which allows you to view complex variables and to evaluate expressions.
Note
The IntelliTrace stand-alone collector does not support capturing snapshots.
See Inspect previous app states using IntelliTrace.
Collect function call information
You can configure IntelliTrace to collect call information for functions. This information lets you see a history of the call stack and lets you step backward and forward through calls in the code. For each function call, IntelliTrace records this data:
- Function name
- Values of primitive data types passed as parameters at function entry points and returned at function exit points
- Values of automatic properties when they are read or changed
- Pointers to first-level child objects, but not their values other than if they were null or not
Note
IntelliTrace collects only the first 256 objects in arrays and the first 256 characters for strings.
See Inspect your app with historical debugging.
Collect module information
To control how much call information that IntelliTrace collects, specify only those modules that you care about. This can help improve your application's performance during collection. See the section Control how much information IntelliTrace Collects in IntelliTrace features.
Will IntelliTrace slow down my application?
By default, IntelliTrace collects data for selected IntelliTrace events only. This might or might not slow down your application, depending on the structure and organization of your code. For example, if IntelliTrace records an event often, this might slow down your application. It might also make you consider refactoring your application.
Collecting call information might slow down your application significantly. It might also increase the size of any IntelliTrace log files (.iTrace files) that you're saving to disk. To minimize these effects, collect call information only for the modules you care about. To change the maximum size of your .iTrace files, go to Tools, Options, IntelliTrace, Advanced.