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Linq Expression tree compiling non-trivial object constants and somehow referring to them

Usually, when compiling an expression tree, I would have thought constants which are not primitives types or strings would be impossible. However, this code:
public class A
{ public int mint = -1; }
public static void Main(String[] pArgs)
{
//Run(pArgs);
Action pact = Thing();
pact();
}
public static Action Thing()
{
var a = new A();
a.mint = -1;
LambdaExpression p =
Expression.Lambda<Action>(Expression.Assign(Expression.Field(Expression.Constant(a, typeof(A)), Strong.Instance<A>.Field<int>(b => b.mint)), Expression.Constant(3, typeof(int))));
return ((Expression<Action>)p).Compile();
}
not only compiles but it actually runs! If you run the compiled method in the Thing() method, then you can actually see the variable a change its field from -1 to 3
I don't see how this makes sense/is possible. How can a method refer to a local variable outside its scope (when inspecting the IL of Thing(), the variable a is just a standard local variable, not on the heap like with a closure). Is there some kind of hidden context past around? How can pact run in Main when the local variable a has presumably been removed from the stack!

How can a method refer to a local variable outside its scope
It can't, and it doesn't.
It can sometimes refer to the object the local variable points to though.
Whether it can or not depends on which way the expression is compiled or otherwise used.
There are three ways that Expressions itself will compile an expression into a method:
Compilation with Compile() to IL in a DynamicMethod.
Compilation to IL in with CompileToMethod() (not available in all versions.
Compilation with Compile() into an interpreted set of instructions with a thunk delegate that runs the interpretation.
The first is used if IL compilation is available, unless true is passed to prefer interpretation (on those version with that overload) and interpretation is not also available. Here an array is used for the closure and it is much the same as closing over a local is, in a delegate.
The second is used to write to another assembly and cannot close in this way. Many constants that will work with Compile() will not work with CompileToMethod() for this reason.
The third is used if IL compilation is not available, or true was passed in those versions that have that overload to prefer interpretation. Here a reference to the object is put into an array of "constants" that the interpreter can then refer to.
The other possibility is that something else interprets the expression entirely, e.g. in producing SQL code. Generally this will fail with non-primitive constants other than string though, but if the query processor is aware of the type of the constant (e.g. if it is of a type of entity that it knows about) then code to produce the equivalent to that entity could be produced.

It is only a that is a local variable; the actual object (from new A()) was always on the heap. When you used Expression.Constant(a, typeof(A)), it wasn't a that you put in as a constant - it was the value of a, i.e. the object reference. So: the scope of a is irrelevant as far as the tree is concerned. This is actually exactly how captured variables (closures) are usually implemented by the compiler (although you don't see it usually, and the C#-based expression compiler doesn't allow assignment operators), so as far as the expression tree is concerned: this is business as usual.
As a comparable example using the C# expression compiler, see here, where
public void M() {
int mint = -1;
Expression<Func<int>> lambda = () => mint;
}
compiles to:
[CompilerGenerated]
private sealed class <>c__DisplayClass0_0
{
public int mint;
}
public void M()
{
<>c__DisplayClass0_0 <>c__DisplayClass0_ = new <>c__DisplayClass0_0();
<>c__DisplayClass0_.mint = -1;
Expression.Lambda<Func<int>>(Expression.Field(Expression.Constant(<>c__DisplayClass0_, typeof(<>c__DisplayClass0_0)), FieldInfo.GetFieldFromHandle((RuntimeFieldHandle)/*OpCode not supported: LdMemberToken*/)), Array.Empty<ParameterExpression>());
}

Inconsistent result when comparing Actions/Funcs

I have been trying to cache the results of certain Actions and Funcs.
For that purpose I am storing the Actions/Funcs in a Dictionary with their respective result.
Whilst doing this I stumbled upon something unexpected (example is simplified):
var lstActions = new List<Action>();
for (int i = 0; i < 2; i++)
{
lstActions.Add(() => { });
}
bool bEqual = lstActions[0] == lstActions[1]; // Result = true
--
var lstActions = new List<Action>();
lstActions.Add(() => { });
lstActions.Add(() => { });
bool bEqual = lstActions[0] == lstActions[1]; // Result = false
Can anyone explain why the results are different?

You're seeing implementation details about how the compiler transforms lambda expressions into delegates that point to compiler-generated methods.
This behavior may change due to changes in the compiler, debug vs. release builds, or changes in the contents of any of the lambdas.
To explain your current behavior:
Every lambda that appears in source is compiled to a separate method. Therefore, your second example generates two methods (which happen to have identical bodies), and the delegates are not the same.
Your first example only has one lambda in the source, so it compiles to a single method. Because the lambda doesn't use any local variables, it doesn't generate a closure class, so the both the Method and Target properties of the delegates are the same.

The compiler tries to minimize the amount of delegate objects it creates. To this end it often caches instances where this is possible.
Since your first example you define a single lambda and it does not capture any loop variables, a single delegate instance will suffice.
In the second example, you defined two different anonymous methods, the compiler will not check that their code is identical as this is a rare case, and will create two delegate instances.
This is however an implementation detail of the compiler and I would not rely on it in any way.

Creating two delegate instances to the same anonymous method are not equal

Consider the following example code:
static void Main(string[] args)
{
bool same = CreateDelegate(1) == CreateDelegate(1);
}
private static Action CreateDelegate(int x)
{
return delegate { int z = x; };
}
You would imagine that the two delegate instances would compare to be equal, just as they would when using the good old named method approach (new Action(MyMethod)). They do not compare to be equal because the .NET Framework provides a hidden closure instance per delegate instance. Since those two delegate instances each have their Target properties set to their individual hidden instance, they do not compare. One possible solution is for the generated IL for an anonymous method to store the current instance (this pointer) in the target of the delegate. This will allow the delegates to compare correctly, and also helps from a debugger standpoint since you will see your class being the target, instead of a hidden class.
You can read more about this issue in the bug I submitted to Microsoft. The bug report also gives an example of why we are using this functionality, and why we feel it should be changed. If you feel this to be an issue as well, please help support it by providing rating and validation.
https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=489518
Can you see any possible reason why the functionality should not be changed? Do you feel this was the best course of action to get the issue resolved, or do you recommend that I should take a different route?

I'm not so inclined to think this is a "bug". It appears moreover that you're assuming some behaviour in the CLR that simply does not exist.
The important thing to understand here is that you are returning a new anonymous method (and initialising a new closure class) each time you call the CreateDelegate method. It seems that you are experting the delegate keyword to use some sort of pool for anonymous methods internally. The CLR certainly does not do this. A delegate to the anonymous method (as with a lambda expression) is created in memory each time you call the method, and since the equality operator does of course compare references in this situation, it is the expected result to return false.
Although your suggested behaviour may have some benefits in certain contexts, it would probably be quite complicated to implement, and would more likely lead to unpredictable scenarios. I think the current behaviour of generating a new anonymous method and delegate on each call is the right one, and I suspect this is the feedback you will get on Microsoft Connect as well.
If you are quite insistent on having the behaviour you described in your question, there is always the option of memoizing your CreateDelegate function, which would insure that the same delegate is returned each time for the same parameters. Indeed, because this is so easy to implement, it is probably one of the several reasons why Microsoft did not consider implementing it in the CLR.

EDIT: Old answer left for historical value below the line...
The CLR would have to work out the cases in which the hidden classes could be considered equal, taking into account anything that could be done with the captured variables.
In this particular case, the captured variable (x) isn't changed either within the delegate or in the capturing context - but I'd rather the language didn't require this sort of complexity of analysis. The more complicated the language is, the harder it is to understand. It would have to distinguish between this case and the one below, where the captured variable's value is changed on each invocation - there, it makes a great deal of difference which delegate you call; they are in no way equal.
I think it's entirely sensible that this already-complex situation (closures are frequently misunderstood) doesn't try to be too "clever" and work out potential equality.
IMO, you should definitely take a different route. These are conceptually independent instances of Action. Faking it by coercing the delegate targets is a horrible hack IMO.
The problem is that you're capturing the value of x in a generated class. The two x variables are independent, so they're unequal delegates. Here's an example demonstrating the independence:
using System;
class Test
{
static void Main(string[] args)
{
Action first = CreateDelegate(1);
Action second = CreateDelegate(1);
first();
first();
first();
first();
second();
second();
}
private static Action CreateDelegate(int x)
{
return delegate
{
Console.WriteLine(x);
x++;
};
}
}
Output:
1
2
3
4
1
2
EDIT: To look at it another way, your original program was the equivalent of:
using System;
class Test
{
static void Main(string[] args)
{
bool same = CreateDelegate(1) == CreateDelegate(1);
}
private static Action CreateDelegate(int x)
{
return new NestedClass(x).ActionMethod;
}
private class Nested
{
private int x;
internal Nested(int x)
{
this.x = x;
}
internal ActionMethod()
{
int z = x;
}
}
}
As you can tell, two separate instances of Nested will be created, and they will be the targets for the two delegates. They are unequal, so the delegates are unequal too.

I don't know about the C# specific details of this problem but I worked on the VB.Net equivalent feature which has the same behavior.
The bottom line is this behavior is "By Design" for the following reasons
The first is that in this scenario a closure is unavoidable. You have used a piece of local data within an anonymous method and hence a closure is necessary to capture the state. Every call to this method must create a new closure for a number of reasons. Therefore each delegate will point to an instance method on that closure.
Under the hood a anonymous method / expression is represented by a System.MulticastDelegate derived instance in code. If you look at the Equals method of this class you will notice 2 important details
It is sealed so there is no way for a derived delegate to change the equals behavior
Part of the Equals method does a reference comparison on the objects
This makes it impossible for 2 lambda expressions which are attached to different closures to compare as equals.

I can't think of a situation where I've ever needed to do that. If I need to compare delegates I always use named delegates, otherwise something like this would be possible:
MyObject.MyEvent += delegate { return x + y; };
MyObject.MyEvent -= delegate { return x + y; };
This example isn't great for demonstrating the issue, but I would imagine that there could be a situation where allowing this could break existing code that was designed with the expectation that this is not allowed.
I'm sure there are internal implementation details that also make this a bad idea, but I don't know exactly how anonymous methods are implemented internally.

This behaviour makes sense because otherwise anonymous methods would get mixed up (if they had the same name, given the same body).
You could change your code to this:
static void Main(){
bool same = CreateDelegate(1) == CreateDelegate(1);
}
static Action<int> action = (x) => { int z = x; };
private static Action<int> CreateDelegate(int x){
return action;
}
Or, preferably, since that's a bad way to use it (plus you were comparing the result, and Action doesn't have a return value ... use Func<...> if you want to return a value):
static void Main(){
var action1 = action;
var action2 = action;
bool same = action1 == action2; // TRUE, of course
}
static Action<int> action = (x) => { int z = x; };

Functors when should I use them whats their intended use [closed]

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I Just can't seem to wrap my head around them.
As I understand it's dynamically adding logic to a class. Are classes within the framework prepared for this?
Why should I just extend the class and add the functionality to it in the extension. I would be globally accessible and afaik much easier to maintain.
I've Read there are 4 functor types:
Comparer
Closure
Predicate
Transformer
We should probably Handle each one of them.
p.s. is there something like it in vb?
So I can state I think that lambda expressions are functors. This clears up things for me a bit :) (hehe)
Lambda expressions are functors?
Anonymous functions are functors?
But I asked this question because I ran into another type of fucntors namely these ones:
delegate void FunctorDelegate(int value);
class Addition {
FunctorDelegate _delegate;
public Addition AddDelegate(FunctorDelegate deleg) {
_delegate += deleg;
return this;
}
public int AddAllElements(IList< int> list) {
int runningTotal = 0;
foreach( int value in list) {
runningTotal += value;
_delegate(value);
}
return runningTotal;
}
}
And then calling it with this:
int runningTotal = new Addition()
.AddDelegate(new FunctorDelegate(
delegate(int value) {
if ((value % 2) == 1) {
runningOddTotal += value;
}
}))
.AddDelegate(new FunctorDelegate(
delegate(int value) {
if ((value % 2) == 0) {
runningEvenTotal += value;
}
}))
.AddAllElements(list);
So no fancy lambda style things.
Now I have this example but it isn't at all clear why this is a "good" solution.
Are delegates (functors) used as lambda expressions or anonymous methods "in most cases" just there as a shortcut for the programmer? There are as far as I can see only a few cases where they're actually the prefered choice for a problem.

I think you're confusing terms from different languages. You seem to be using "Functor" in the C++ or Java sense, e.g. see the wikipedia page. In C++, it's an object of a class that overloads the function-call operator, so it can be used as a function but with state.
This is logically the same thing as a delegate bound to an instance method in C# (or any .NET language).
There are three ways to write such a thing. First, you can write an ordinary method, and then assign the name of the method to a delegate variable.
void MyMethod() { Console.WriteLine("Hi!"); }
void Foo()
{
Action a = MyMethod;
a();
}
Second, you can use anonymous method syntax, introduced in C# 2.0:
void Foo()
{
Action a = delegate { Console.WriteLine("Hi!"); }
a();
}
Thirdly, you can use lambda syntax, introduced in C# 3.0:
void Foo()
{
Action a = () => Console.WriteLine("Hi!");
a();
}
The advantage of the last two is that the body of the method can read and write local variables in the containing method.
The advantage of lambda syntax over anon-methods are that it is more succinct and it does type inference on parameters.
Update: The advantage of anon-methods (delegate keyword) over lambdas is that you can omit the parameters altogether if you don't need them:
// correct way using lambda
button.Click += (sender, eventArgs) => MessageBox.Show("Clicked!");
// compile error - wrong number of arguments
button.Click += () => MessageBox.Show("Clicked!");
// anon method, omitting arguments, works fine
button.Click += delegate { MessageBox.Show("Clicked!"); };
I know of only one situation where this is worth knowing, which is when initializing an event so that you don't have to check for null before firing it:
event EventHandler Birthday = delegate { };
Avoids a lot of nonsense elsewhere.
Finally, you mention that there are four kinds of functor. In fact there are an infinity of possibly delegate types, although some authors may have their favourites and there obviously will be some common patterns. An Action or Command takes no parameters and returns void, and a predicate takes an instance of some type and returns true or false.
In C# 3.0, you can whip up a delegate with up to four parameters of any types you like:
Func<string, int, double> f; // takes a string and an in, returns a double
Re: Updated Question
You ask (I think) if there are many use cases for lambdas. There are more than can possibly be listed!
You most often see them in the middle of larger expressions that operate on sequences (lists computed on-the-fly). Suppose I have a list of people, and I want a list of people exactly forty years old:
var exactlyForty = people.Where(person => person.Age == 40);
The Where method is an extension method on the IEnumerable<T> interface, where T in this case is some kind of Person class.
This is known in .NET as "Linq to Objects", but known elsewhere as pure functional programming on sequences or streams or "lazy" lists (all different names for the same thing).

In .NET terms, I think what you are describing is the Delegate - and it exists in all of .NET, not just C#.
I'm not sure that a "closure" would a "type" in the same was as a comparer/predicate/transformer, since in C# terms a closure is simply an implementation detail but can be any of those three.
In .NET, delegates are used in two main ways:
as the eventing mechanism
to provide functional-style programming
The first is important, but it sounds like you are more interested in the second. In reality, they operate much like single-method interfaces... consider:
List<int> vals = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
List<int> evenVals = vals.FindAll(i => i % 2 == 0); // predicate
List<string> valsAsStrings = vals.ConvertAll(i => i.ToString()); // transformer
// sort descending
vals.Sort((x, y) => y.CompareTo(x)); // comparer
A closure is more where we bring additional scope from outside the delegate into the delegate:
int max = int.Parse(Console.ReadLine()); // perhaps 6
List<int> limited = vals.FindAll(i => i <= max);
here the max is captured into the delegate as a closure.
Re "Are classes within the framework prepaired for this?" - many are, and LINQ goes a long way to allowing this even wider. LINQ provides extension methods over (for example) all of IEnumerable<T> - meaning that collections without delegate-based access aquire them for free:
int[] data = { 1,2,3,4,5,6,7,8,9 };
var oddData = data.Where( i => i % 2 == 1 );
var descending = data.OrderBy(i => -i);
var asStrings = data.Select(i => i.ToString());
Here the Where and OrderBy methods are LINQ extension methods that take delegates.

Interesting with terminology; my spontaneous interpretation of the term "Functor" was that it referred to anonymous methods. So that will be my take on it.
These are some of my typical uses:
Comparisons (usually for sorting a list):
List<int> ints = new List<int>();
ints.AddRange(new int[] { 9, 5, 7, 4, 3, 5, 3 });
ints.Sort(new Comparison<int>(delegate(int x, int y)
{
return x.CompareTo(y);
}));
// yes I am aware the ints.Sort() would yield the same result, but hey, it's just
// a conceptual code sample ;o)
// and the shorter .NET 3.5 version:
ints.Sort((x, y) =>
{
return x.CompareTo(y);
});
I will use this approach for comparisons, rather than having it in its own method an using a delegate for that method, in the cases where this particular sort happens in one place only. If it is likely that I will want to use the same comparison somewhere else, it gets to live in its own, reusable method.
Another of my fairly common uses is in unit testing, when the test relies on some event being raised. I have found that to be essential when unit testing workflows in Workflow Foundation:
WorkflowRuntime runtime = WorkflowHost.Runtime;
WorkflowInstance instance = runtime.CreateWorkflow(typeof(CreateFile));
EventHandler<WorkflowEventArgs> WorkflowIdledHandler = delegate(object sender, WorkflowEventArgs e)
{
// get the ICreateFileService instance from the runtime
ISomeWorkflowService service = WorkflowHost.Runtime.GetService<ISomeWorkflowService>();
// set the desired file content
service.DoSomeWork(instance.InstanceId, inputData);
};
// attach event handler
runtime.WorkflowIdled += WorkflowIdledHandler;
instance.Start();
// perform the test, and then detach the event handler
runtime.WorkflowIdled -= WorkflowIdledHandler;
In this case it is simpler to have the event handler declared as anonymous methods since it uses the instance variable that is defined in the unit test method scope. Had I intstead opted to implelment the event handler as its own separate method I would also need to figure out a way for it to pick up instance, probably by introducing a class level member, which would not seem like a perfect design in a unit test class.
There are more cases where I find this in my code, but they usually have one or two things in common:
I have no interest in referencing that piece of code from anywhere else than in that particular place.
The method needs access to data that would be out of the scope for a regular method

The real answer is that a functor is a type of mathematical object, and is "reified" by different languages in different ways. For example, suppose that you have a "container" object that stores a bunch of other objects of the same type. (For example, a set or array) Then, if your language had a method that let you 'map' over the container, so that you could call a method on each object in the container, then the container would be a functor.
In other words, a functor is a container with a method that lets you pass a method to its contained things.
Every language has its own way of doing this, and they sometimes conflate the usage. For example, C++ uses function pointers to represent the "passing in" of a method, and calls the function pointer a "functor." Delegates are just a handle on methods that you can pass in. You are using the terminology "incorrectly", just like C++ does.
Haskell gets it right. You declare that a type implements the functor interface, and then you get the mapping method.
Functions (like lambdas) are functors too, but it can be kind of hard to think of a function as a "container". In short, a function is a "container" around a return value, constructed in such a way that the return value (possibly) depends on the function's arguments.

I'm sure you mean Lambda Expressions. Those are Small Functions you can write very quickly, and they have the characteristic "=>" Operator. These are a new Feature of C# 3.0.
This Example will be a classic Transformer; to use one we need a delegate to define the signature for the Lambda Function.
delegate int Transformer(int i);
Now Declare a Lambda with this delegate:
Transformer sqr = x => x * x;
We can use it like a normal function:
Console.WriteLine(sqr(3)); //9
These are used in LINQ Queries a lot, for example to Sort (Comparer), to Search through (Predicate).
The book "C# Pocket Reference" (apart from beign the best around in my opinion, has a very good part on Lambdas. (ISBN 978-0-596-51922-3 )

Events in lambda expressions - C# compiler bug?

I was looking at using a lamba expression to allow events to be wired up in a strongly typed manner, but with a listener in the middle, e.g. given the following classes
class Producer
{
public event EventHandler MyEvent;
}
class Consumer
{
public void MyHandler(object sender, EventArgs e) { /* ... */ }
}
class Listener
{
public static void WireUp<TProducer, TConsumer>(
Expression<Action<TProducer, TConsumer>> expr) { /* ... */ }
}
An event would be wired up as:
Listener.WireUp<Producer, Consumer>((p, c) => p.MyEvent += c.MyHandler);
However this gives a compiler error:
CS0832: An expression tree may not contain an assignment operator
Now at first this seems reasonable, particularly after reading the explanation about why expression trees cannot contain assignments. However, in spite of the C# syntax, the += is not an assignment, it is a call to the Producer::add_MyEvent method, as we can see from the CIL that is produced if we just wire the event up normally:
L_0001: newobj instance void LambdaEvents.Producer::.ctor()
L_0007: newobj instance void LambdaEvents.Consumer::.ctor()
L_000f: ldftn instance void LambdaEvents.Consumer::MyHandler(object, class [mscorlib]System.EventArgs)
L_0015: newobj instance void [mscorlib]System.EventHandler::.ctor(object, native int)
L_001a: callvirt instance void LambdaEvents.Producer::add_MyEvent(class [mscorlib]System.EventHandler)
So it looks to me like this is a compiler bug as it's complaining about assignments not being allowed, but there is no assignment taking place, just a method call. Or am I missing something...?
Edit:
Please note that the question is "Is this behaviour a compiler bug?". Sorry if I wasn't clear about what I was asking.
Edit 2
After reading Inferis' answer, where he says "at that point the += is considered to be assignment" this does make some sense, because at this point the compiler arguably doesn't know that it's going to be turned into CIL.
However I am not permitted to write the explicit method call form:
Listener.WireUp<Producer, Consumer>(
(p, c) => p.add_MyEvent(new EventHandler(c.MyHandler)));
Gives:
CS0571: 'Producer.MyEvent.add': cannot explicitly call operator or accessor
So, I guess the question comes down to what += actually means in the context of C# events. Does it mean "call the add method for this event" or does it mean "add to this event in an as-yet undefined manner". If it's the former then this appears to me to be a compiler bug, whereas if it's the latter then it's somewhat unintuitive but arguably not a bug. Thoughts?

In the spec, section 7.16.3, the += and -= operators are called "Event assignment" which certainly makes it sound like an assignment operator. The very fact that it's within section 7.16 ("Assignment operators") is a pretty big hint :) From that point of view, the compiler error makes sense.
However, I agree that it is overly restrictive as it's perfectly possible for an expression tree to represent the functionality given by the lambda expression.
I suspect the language designers went for the "slightly more restrictive but more consistent in operator description" approach, at the expense of situations like this, I'm afraid.

+= is an assignment, no matter what it does (e.g. add an event). From the parser point of view, it is still an assignment.
Did you try
Listener.WireUp<Producer, Consumer>((p, c) => { p.MyEvent += c.MyHandler; } );

Actually, as far as the compiler is concerned at that point, it is an assignment.
The += operator is overloaded, but the compiler doesn't care about that at it's point. After all, you're generating an expression through the lambda (which, at one point will be compiled to actual code) and no real code.
So what the compiler does is say: create an expression in where you add c.MyHandler to the current value of p.MyEvent and store the changed value back into p.MyEvent. And so you're actually doing an assignment, even if in the end you aren't.
Is there a reason you want the WireUp method to take an expression and not just an Action?

Why do you want to use the Expression class? Change Expression<Action<TProducer, TConsumer>> in your code to simply Action<TProducer, TConsumer> and all should work as you want. What you're doing here is forcing the compiler to treat the lambda expression as an expression tree rather than a delegate, and an expression tree indeed cannot contain such assignments (it's treated as an assignment because you're using the += operator I believe). Now, a lambda expression can be converted into either form (as stated on [MSDN][1]). By simply using a delegate (that's all the Action class is), such "assignments" are perfectly valid. I may have misunderstood the problem here (perhaps there is a specific reason why you need to use an expression tree?), but it does seem like the solution is fortunately this simple!
Edit: Right, I understand your problem a bit better now from the comment. Is there any reason you can't just pass p.MyEvent and c.MyHandler as arguments to the WireUp method and attach the event handler within the WireUp method (to me this also seems better from a design point of view)... would that not eliminate the need for an expression tree? I think it's best if you avoid expression trees anyway, as they tend to be rather slow compared to delegates.

I think the problem is, that apart from the Expression<TDelegate> object, the expression tree is not statically typed from the perspective of the compiler. MethodCallExpression and friends do not expose static typing information.
Even though the compiler knows all the types in the expression, this information is thrown away when converting the lambda expression to an expression tree. (Have a look at the code generate for expression trees)
I would nonetheless consider submitting this to microsoft.