NET Debugging : Visual Studio (part 1) - SOS Integration

Visual Studio is an extremely popular integrated developer environment among developers. The power of this IDE coupled with its ease of use makes it the environment of choice for .NET developers today. As part of the Visual Studio integrated experience comes a highly sophisticated debugger that can be used to perform troubleshooting on a myriad of different problems, such as using source-level debugging, script debugging, and SQL debugging. The one area where Visual Studio debugging has lacked functionality is in production-level debugging where we either need to work with post mortem dump files or have access to the internals of the CLR (such as the SOS commands). Fortunately, the Visual Studio team recognized and addressed the latter part of the problem by making Visual Studio compatible with the SOS debugger extension.

1. SOS Integration

To illustrate how the SOS debugger extension can be integrated into Visual Studio, start by creating a simple C# project (command-line application will suffice). After the project has been created, set a breakpoint on the first line of code and start debugging by pressing F5. Figure 1 shows the debugger after the breakpoint has been hit.

Figure 1. Breakpoint hit in Visual Studio

The next step in the SOS integration process is to bring up the intermediate window. The intermediate window is used to execute various commands (such as variable assignments, expression evaluations, etc.) during a debugging session. Figure 2 shows how to enable the Immediate Window.

Figure 2. Enabling the Immediate Window

After the Immediate Window has been enabled, you can begin entering debugging commands. One of the commands available at our disposal is the load command, which can be used to load the SOS debugger extension. Figure 3 illustrates the result of executing the load command.

Figure 3. Using the load command to load the SOS debugger extension

The net result of using the load command is that Visual Studio fails by stating that unmanaged debugging support must be enabled for the project. Figure 4 illustrates the process of enabling unmanaged debugging support.

Figure 4. Enabling unmanaged debugging support

Start by right-clicking the project in Solution Explorer followed by selecting the Properties context menu item, which brings up the properties page on the right side. In the properties page, select the Debug tab and check the Enable Unmanaged Code Debugging checkbox.

After unmanaged code debugging has been enabled, you can restart the debugging session, issue the load SOS command, and start using the SOS debugger extension commands in the Immediate Window (see Figure 5).

Figure 5. Using the SOS debugger extension

In Figure 5, we used two SOS commands (EEVersion and DumpHeap) to illustrate what the output looks like in the Immediate Window.

Combining the power and ease of Visual Studio with the in-depth CLR knowledge of SOS creates a single, integrated experience for complex debugging scenarios.