Getting a Method's Return Value in the VS Debu

Question

Is it possible to get a method's return value in the Visual Studio debugger, even if that value isn't assigned to a local variable? For example, I'm debugging the following code:

public string Foo(int valueIn)
{
    if (valueIn > 100)
        return Proxy.Bar(valueIn);
    else
        return "Not enough";
}

Since I'm not setting any local variables in Foo, and assuming I'm not setting a break point in whatever's calling Foo, is there a way to see what the return value is if I have a breakpoint inside of Foo (or another way)? I don't have much experience with the Autos or Intermediate windows, so I'm not sure if those are even a valid option or not.

Answer 1

You can set a breakpoint in Foo, open the immediate window and run the following command:

? Foo(valueIn)

This will print the return value in the Immediate Window.

You can also copy the expression and paste it into the Watch window, though I would do this only if I am certain that the call has no side effects (otherwise you can get confusing results).

Answer 2

Visual Studio 2013 now has the ability in the Autos window to display the last value returned by a function, alleviating the need to re-execute it in the Output window or introduce a temporary variable:

http://blogs.msdn.com/b/visualstudioalm/archive/2013/06/27/seeing-function-return-values-in-the-debugger-in-visual-studio-2013.aspx

Answer 3

You can always switch to disassembler view and step through the individual instructions. The return value will be in @eax (or @rax) just before you execute the 'ret' instruction.

Answer 4

No, I don't know of a way to do this. I would put a breakpoint in the caller and look at the return value there.

Answer 5

You can also highlight any expression in the debugger and right-click -> quick watch. That will execute the expression (assuming it's valid) and give you the value.

Answer 6

You can always use your watch box to evaluate function calls.

Foo(valueIn);

This will only work if your Proxy.Bar(valueIn) is time independent though.