How to set a breakpoint in managed code using WinDBG?

E.g., breakpoints in the Main method and System.String.Contains method using the following console application:

namespace ConsoleHelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            string foo = "The Unimaginary Friend";

            Console.ReadLine();

            if (!foo.Contains("Hello"))
            {
                Console.WriteLine("Inside if block.");
            }
        }
    }
}

Code Already JITTED

If the code is already JITTED, i.e., the code was already compiled from bytecode to machine code, then you can set a breakpoint using bp.

E.g.:

Let the program run and pause at Console.ReadLine().

0:003> .loadby sos clr
0:003> !EEStack
...
00c3ef94 738d2a0c (MethodDesc 736060a0 +0x11c System.IO.StreamReader.ReadLine())
00c3efb0 740551ad (MethodDesc 736ad9e0 +0x19 System.IO.TextReader+SyncTextReader.ReadLine())
00c3efc0 73f54392 (MethodDesc 735f31fc +0x12 System.Console.ReadLine())
00c3efc8 00e500c1 (MethodDesc 00d437a4 +0x71 ConsoleHelloWorld.Program.Main(System.String[]))
...

Find the address of String.Contains() using:

!name2ee *!System.String.Contains

The output tells you the code is already JITTED:

Module:      73571000
Assembly:    mscorlib.dll
Token:       0600033a
MethodDesc:  735fa768
Name:        System.String.Contains(System.String)
JITTED Code Address: 73f21734

Set a breakpoint using bp:

bp 73f21734

Continue the execution, press ENTER and wait until the breakpoint is hit:

0:003> g
Breakpoint 0 hit
eax=028c1228 ebx=00c3f08c ecx=028c2398 edx=028c241c esi=00000000 edi=00c3f000
eip=73f21734 esp=00c3efcc ebp=00c3efe8 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000202
mscorlib_ni+0x9b1734:
73f21734 6a00            push    0

Done! The callstack looks like this:

0:000> !CLRStack
OS Thread Id: 0x13d4 (0)
Child SP       IP Call Site
0092f420 73f21734 System.String.Contains(System.String)
0092f424 00ba009e ConsoleHelloWorld.Program.Main(System.String[]) [c:\ConsoleHelloWorld\Program.cs @ 17]
0092f5c0 746c2552 [GCFrame: 0092f5c0]

The stack objects look like this:

0:000> !dso
ESP/REG  Object   Name
eax      028c1228 System.String    
ecx      02602398 System.String    The Unimaginary Friend
edx      026023d4 System.String    Hello
00C3EFD0 028c1228 System.String
...

Code Not JITTED Yet

As soon as the debugger starts, configure the debugger to break when clrjit.dll loads:

sxe ld clrjit

Once clrjit.dll is loaded, look for the method address:

!name2ee ConsoleHelloWorld.exe ConsoleHelloWorld.Program.Main

The output tells you the method is not JITTED yet:

Module:      009d2edc
Assembly:    ConsoleHelloWorld.exe
Token:       06000001
MethodDesc:  009d37a4
Name:        ConsoleHelloWorld.Program.Main(System.String[])
Not JITTED yet. Use !bpmd -md 009d37a4 to break on run.

Set a breakpoint using !bpmd:

!bpmd -md 009d37a4

The breakpoint is pending:

MethodDesc = 009d37a4
Adding pending breakpoints...

Continue the execution. Then, the code is JITTED and the breakpoint is hit:

JITTED ConsoleHelloWorld!ConsoleHelloWorld.Program.Main(System.String[])
Setting breakpoint: bp 00BA007B [ConsoleHelloWorld.Program.Main(System.String[])]
Breakpoint 0 hit

Done! The callstack looks like this:

0:000> !CLRStack
OS Thread Id: 0x252c (0)
Child SP       IP Call Site
008cece4 00b3007b ConsoleHelloWorld.Program.Main(System.String[]) [c:\ConsoleHelloWorld\Program.cs @ 12]
008cee78 746c2552 [GCFrame: 008cee78]

Sources: walter’s log, SOS Debugging Extension