C# delegate instantiation syntax

Question

I have seen different forms of instantiating a delegate object. For example:

I have the following delegate and method.

public delegate void Delegate();
public void foo();

And these two options for instantiation.

Delegate del = new Delegate(foo);
Delegate del = foo;

My question is as follows: What is the semantic difference between these two statements?

score 2 · Accepted Answer · answered Sep 04 '14 at 23:55

2

The short answer is none.

The long answer is, they both compile to the same IL.

Delegate del1 = foo;
Delegate del2 = new Delegate(foo);

compiles to

IL_0001:  ldarg.0     
IL_0002:  ldftn       UserQuery.foo
IL_0008:  newobj      UserQuery+Delegate..ctor
IL_000D:  stloc.0     // del1
IL_000E:  ldarg.0     
IL_000F:  ldftn       UserQuery.foo
IL_0015:  newobj      UserQuery+Delegate..ctor
IL_001A:  stloc.1     // del2

answered Sep 04 '14 at 23:55

Andrew Cooper

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@RihardMarius There are plenty of tools. You can instruct the C# compiler to dump it out - or get a tool like ILSpy, Dotpeek, Reflector, etc. – Simon Whitehead Sep 05 '14 at 00:32
@RihardMarius I used LinqPad. It's an awesome tool for quickly prototyping and running C# code snippets. – Andrew Cooper Sep 05 '14 at 15:10

score 2 · Answer 2 · answered Sep 04 '14 at 23:55

Absolutely nothing. The compiler will convert the second one into an instantiation of Delegate just like the first one:

// Delegate del = new Delegate(foo);
ldftn    void App.Program::foo()
newobj   instance void App.Program/Delegate::.ctor(object, native int)
stloc.0

// Delegate de2l = foo;
ldftn    void App.Program::foo()
newobj   instance void App.Program/Delegate::.ctor(object, native int)
stloc.1

score 1 · Answer 3 · edited May 23 '17 at 12:01

1

Nothing to my knowledge. The compiler will generate the new for you. A similar question was answered here. This shortcut method was introduced from C# 2.0 onwards - MSDN.

edited May 23 '17 at 12:01

Community

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answered Sep 05 '14 at 00:09

Fuzzyllama

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3

thank you for the link, I swear I did a search and didn't found anything close to my question. – Ricardo Zorio Sep 09 '14 at 15:48

C# delegate instantiation syntax

3 Answers3