var tmp = new Person();
tmp.Name = "Jonh";
tmp.Age = 42;
var person = tmp;

namespace TestObjectCollectionInitializers
{
    class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var person = new Person { Name = "Jonh", Age = 42 };
        }
    }
}

.method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       26 (0x1a)
  .maxstack  2
  .locals init ([0] class TestObjectCollectionInitializers.Person '<>g__initLocal0')
  IL_0000:  newobj     instance void TestObjectCollectionInitializers.Person::.ctor()
  IL_0005:  stloc.0
  IL_0006:  ldloc.0
  IL_0007:  ldstr      "Jonh"
  IL_000c:  callvirt   instance void TestObjectCollectionInitializers.Person::set_Name(string)
  IL_0011:  ldloc.0
  IL_0012:  ldc.i4.s   42
  IL_0014:  callvirt   instance void TestObjectCollectionInitializers.Person::set_Age(int32)
  IL_0019:  ret
} // end of method Program::Main

namespace TestObjectCollectionInitializers
{
    class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var person = new Person { Name = "Jonh", Age = 42 };
            var name = person.Name;
        }
    }
}

.method private hidebysig static void  Main(string[] args) cil managed
{
  .entrypoint
  // Code size       35 (0x23)
  .maxstack  2
  .locals init ([0] class TestObjectCollectionInitializers.Person person,
           [1] class TestObjectCollectionInitializers.Person '<>g__initLocal0')
  IL_0000:  newobj     instance void TestObjectCollectionInitializers.Person::.ctor()
  IL_0005:  stloc.1            // в 1 - tmp
  IL_0006:  ldloc.1            // this для set_Name()
  IL_0007:  ldstr      "Jonh"  //value для set_Name()
  IL_000c:  callvirt   instance void TestObjectCollectionInitializers.Person::set_Name(string)
  IL_0011:  ldloc.1            // this для set_Age()
  IL_0012:  ldc.i4.s   42      //value для set_Age()
  IL_0014:  callvirt   instance void TestObjectCollectionInitializers.Person::set_Age(int32)
  IL_0019:  ldloc.1            // Load local variable 1 onto stack. (tmp)
  IL_001a:  stloc.0            // Pop a value from stack into local variable 0. (person)
  IL_001b:  ldloc.0            // this для get_Name()
  IL_001c:  callvirt   instance string TestObjectCollectionInitializers.Person::get_Name()
  IL_0021:  pop
  IL_0022:  ret
} // end of method Program::Main