How to attach a debugger at process creation?

Question

I would like to debug a .NET application that fails immediately on startup (and exists without an error message or log), but I can't attach a debugger to it because the process exists almost immediately after I run it. I don't have the source code for the app, so I can't do "Start Debugging". I tried using a Visual Studio macro to start a process, attach to it, then break, but the macro is too slow and by the time it finds the process, the process has already exited:

Imports System
Imports EnvDTE80
Imports EnvDTE90
Imports System.Diagnostics

Public Module Module1
    Sub RunAndAttach()
        Try
            Dim dbg As Debugger3 = DTE.Debugger
            Dim trans As Transport = dbg.Transports.Item("Default")
            Dim sysProc As Process = System.Diagnostics.Process.Start(New ProcessStartInfo("C:\Temp\CrashingApp.exe") With {.WorkingDirectory = "C:\Temp"})
            Dim proc As EnvDTE90.Process3 = dbg.GetProcesses(trans, "ALLON-PC").Item("CrashingApp.exe")
            If (Not sysProc.HasExited) Then
                proc.Attach()
                proc.Break(False)
            Else
                MsgBox("Process " + proc.Name + " has already has exited.")
            End If
        Catch ex As System.Exception
            MsgBox(ex.Message)
        End Try
    End Sub

End Module

Is there a way to attach the debugger to a newly created process, like F5 does?

Thanks!

Answer 1

1. You can use windbg from it you can start the process.
2. You can use reflector to decompile and get the source and continue from there.

Another idea is to use process monitor to see what the process is trying to do. The fail is most probably caused by a dependency on some external thing. And process monitor can help you locate it.

Update: You can use the reflector FileDisassembler add-in to create the full solution and debug it from there.

Answer 2

The debugger requires a certain amount of processing to happen before it can be attached. For example in ASP.Net, it's hard to debug "Application_Start" events on IIS, because it's too early - the application has to be started before a debugger can be attached.

You can execute your program in Windbg though and get an immediate break or memory dump. There's a great tutorial on setting up windbg here, and in some of the comments on the post there are instructions on how to run your .exe from within windbg and get an immediate dump.

Answer 3

I think you can just do "File\Open\Project/Solution", select the .exe as the "solution", and then hit F5.

Answer 4

1. Create a new project (a console project is fine).
2. Right-click the project and choose "Properties".
3. Click the "Debug" tab.
4. Choose "Start External Program:"
5. Select the program.
6. Hit F5.