Does passing a struct into an interface field allocate?

Question

I have a structure something like this

struct MyStructure
    :IFoo
{
}

and a method like this:

public BarThisFoo(IFoo a)
{

}

my question is does passing the structure into that method "box" the structure, thus causing a garbage allocation?

Addendum: Before anyone says it, garbage collection is not free in this application, it's actually very sensitive to garbage collections, so allocation free code is important.

Answer 1

To avoid boxing you can use generics with constraints:

struct MyStructure
    :IFoo
{
}

public void BarThisFoo<T>(T a) where T : IFoo
{

}

See J. Richter CLR via C#, 2nd edition, chapter 14: Interfaces, section about Generics and Interface Constraints.

EDIT:

Example code

using System;
using System.Collections;

interface IFoo {
    void Foo();
}
struct MyStructure : IFoo {
    public void Foo() {
    }
}
public static class Program {
    static void BarThisFoo<T>(T t) where T : IFoo {
        t.Foo();
    }
    static void Main(string[] args) {
        MyStructure s = new MyStructure();
        BarThisFoo(s);
    }
}

IL code for method Main doesn't contain any box instructions:

.method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       15 (0xf)
  .maxstack  1
  .locals init ([0] valuetype MyStructure s)
  IL_0000:  ldloca.s   s
  IL_0002:  initobj    MyStructure
  IL_0008:  ldloc.0
  IL_0009:  call       void Program::BarThisFoo<valuetype MyStructure>(!!0)
  IL_000e:  ret
} // end of method Program::Main