Debug multiple processes (C#, Visual Basic, C++)

Applies to: Visual Studio Visual Studio for Mac

Visual Studio can debug a solution that has several processes. You can start and switch between processes, break, continue, and step through source, stop debugging, and end or detach from individual processes.

Start debugging with multiple processes

When more than one project in a Visual Studio solution can run independently, you can select which project the debugger starts. The current startup project appears in bold in Solution Explorer.

To change the startup project, in Solution Explorer, right-click a different project and select Set as StartUp Project.

To start debugging a project from Solution Explorer without making it the startup project, right-click the project and select Debug > Start new instance or Step into new instance.

To set the startup project or multiple projects from solution Properties:

1. Select the solution in Solution Explorer and then select the Properties icon in the toolbar, or right-click the solution and select Properties.

2. On the Properties page, select Common Properties > Startup Project.

   

3. Select Current selection, Single startup project and a project file, or Multiple startup projects.

   If you select Multiple startup projects, you can change the startup order and action to take for each project: Start, Start without debugging, or None.

4. Select Apply, or OK to apply and close the dialog.

Attach to a process

The debugger can also attach to apps running in processes outside of Visual Studio, including on remote devices. After you attach to an app, you can use the Visual Studio debugger. Debugging features might be limited. It depends on whether the app was built with debug information, whether you have access to the app's source code, and whether the JIT compiler is tracking debug information.

For more information, see Attach to running processes.

To attach to a running process:

1. With the app running, select Debug > Attach to Process.

   

2. In the Attach to Process dialog box, select the process from the Available Processes list, and then select Attach.

Use the Registry Editor to automatically start a process in the debugger

Sometimes, you might need to debug the startup code for an app that is launched by another process. Examples include services and custom setup actions. You can have the debugger launch and automatically attach to the app.

1. Start the Windows Registry Editor by running regedit.exe.

2. In Registry Editor, navigate to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options.

3. Select the folder of the app that you want to start in the debugger.

   If the app isn't listed as a child folder, right-click Image File Execution Options, select New > Key, and type the app name. Or, right-click the new key in the tree, select Rename, and then enter the app name.

4. Right-click the new key in the tree and select New > String Value.

5. Change the name of the new value from New Value #1 to debugger.

6. Right-click debugger and select Modify.

   

7. In the Edit String dialog box, type vsjitdebugger.exe in the Value data box, and then select OK.

   

Debug with multiple processes

When debugging an app with several processes, the breaking, stepping, and continuing debugger commands affect all processes by default. For example, when a process is suspended at a breakpoint, the execution of all other processes is also suspended. You can change this default behavior, to gain more control over the targets of execution commands.

To change whether all processes are suspended when one process breaks:

• Under Tools (or Debug) > Options > Debugging > General, select or clear the Break all processes when one process breaks check box.

Break, step, and continue commands

The following table describes the behaviors of debugging commands when the Break all processes when one process breaks check box is selected or deselected:

Find the source and symbol (.pdb) files

To navigate the source code of a process, the debugger needs access to its source files and symbol files. For more information, see Specify symbol (.pdb) and source files.

If you can't access the files for a process, you can navigate by using the Disassembly window. For more information, see How to: Use the Disassembly window.

Switch between processes

You can attach to multiple processes when you're debugging, but only one process is active in the debugger at any given time. You can set the active or current process in the Debug Location toolbar, or in the Processes window. To switch between processes, both processes must be in break mode.

To set the current process from the Debug Location toolbar:

1. To open the Debug Location toolbar, select View > Toolbars > Debug Location.

2. During debugging, on the Debug Location toolbar, select the process you want to set as the current process from the Process dropdown.

   

To set the current process from the Processes window:

1. To open the Processes window, while debugging, select Debug > Windows > Processes.

2. In the Processes window, the current process is marked by a yellow arrow. Double-click the process you want to set as the current process.

   

Switching to a process sets it as the current process for debugging purposes. Debugger windows show the state for the current process, and stepping commands affect only the current process.

Stop debugging with multiple processes

By default, when you select Debug > Stop Debugging, the debugger ends or detaches from all processes.

• If the current process was launched in the debugger, the process is ended.

• If you attached the debugger to the current process, the debugger detaches from the process and leaves the process running.

If you start debugging a process from a Visual Studio solution, then attach to another process that is already running, and then choose Stop Debugging, the debugging session ends. The process that was started in Visual Studio ends, while the process you attached to keeps running.

To control the way that Stop Debugging affects an individual process, in the Processes window, right-click a process, and then select or clear the Detach when debugging stopped check box.

Stop, terminate, and detach commands

The following table describes the behaviors of the debugger stop, terminate, and detach commands with multiple processes:

See also

• Specify symbol (.pdb) and source files
• Attach to running processes
• Navigating through code with the debugger
• Just-In-Time debugging
• Debug multithreaded applications