Managed Debugging Assistants are an existing feature (Customer Debug Probes) improved on and expanded. They are exposed in a similar manner to exceptions (don't let that scare you) but occur not because of an error condition, but because the runtime has noticed a condition that could cause you problems. We've talked to lots of customers over the years and have received feedback that there are a set of scenarios that cause developers pain more often than others. As a result, we've written a bunch of code -- the MDAs themselves -- that can be used while your code is running to protect you against these pain points ... that's good, right?
The MDA infrastructure is always "on", but only a few MDAs are activated by default. That's easily changed, by selecting the "Debug" menu and "Exceptions" within it. From there, you can turn on or off any MDA of your choosing, as you can see in the image below. There is only one MDA turned on in that part of list in the image below, but you turn on as many as you want.
Anyway, I want to introduce you to the LoadFromContext MDA. If you want to know more about the joys of LoadFrom, check out Suzanne's blog. I'll post more on binding contexts at some point, but want to stay on the subject of this MDA for the moment. Here is some code that exercises this MDA -- this is just an exe project attempting to load a built assembly from a class library project in the same solution (hence the strange pathing) ...
using System;
using System.Reflection;
namespace LoadFromMDA
{
class Program
{
static void Main(string[] args)
{
Assembly asm = Assembly.LoadFrom(@"..\..\..\SomeAssembly\bin\debug\SomeAssembly.dll");
Console.WriteLine(asm.FullName);
}
}
}
If the MDA is enabled, I get the following exception-looking popup window as soon as hit the first line of code.
The reason that this MDA is so useful is that it is really quite difficult to determine for certain which binding context an assembly was loading into, other than following a certain set of rules and closely watching the way that the binder binds to dependent assemblies. However, with this MDA, you can know for sure if you are loading assemblies into the LoadFrom context.
There are several other MDAs to play with. I recommend taking a look through them and turning on ones that might apply to your program. There is no harm and you may avoid your program throwing an exception in some edge-case scenarios for reasons that may not be super clear to you.