Solving this in my mind gives 7 for the first and 9 for the second with exact same reasoning as Cetin showed.

But I would always prefer to write this directly without ++, --, etc., since it makes some confusion.

>Following code
>
>I thought I would get 9 but I get 7
>

>	int i = 1;
>
>	i += (i += 2) + 3;
>
>	Console.WriteLine("{0}", i);
>	Console.ReadLine();
>

>
>Reason:
>The value of i is loaded at the beginning of the operation and not at the end just before the addition is done
>
>

>  .locals init ([0] int32 i)
>  IL_0000:  nop
>  IL_0001:  ldc.i4.1
>  IL_0002:  stloc.0   
>  IL_0003:  ldloc.0    // load i  for the first +=
>  IL_0004:  ldloc.0   // load i   for the second +=
>  IL_0005:  ldc.i4.2 
>  IL_0006:  add     
>  IL_0007:  dup
>  IL_0008:  stloc.0   // this is (i += 2) that is stored in i
>  IL_0009:  ldc.i4.3
>  IL_000a:  add
>  IL_000b:  add    // this is the original value of i, loaded in IL_0003
>  IL_000c:  stloc.0  // i is overwritten
>

>
>But this gives 9
>

>	int i = 1;
>
>	i += 2;
>	i += i + 3;
>

>
>

>IL_0000:  nop
>  IL_0001:  ldc.i4.1
>  IL_0002:  stloc.0
>  IL_0003:  ldloc.0
>  IL_0004:  ldc.i4.2
>  IL_0005:  add
>  IL_0006:  stloc.0
>  IL_0007:  ldloc.0
>  IL_0008:  ldloc.0
>  IL_0009:  ldc.i4.3
>  IL_000a:  add
>  IL_000b:  add
>  IL_000c:  stloc.0
>