c# - Why use System.Threading.Interlocked.Decrement instead of minus? -

I changed some c # code on vb.net and converter. Tilik.com started it:

  i--;  

In this:

  System.Math.Max ​​(System.Threading.Interlocked.Decrement (i), i + 1)  
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 The current terminology for C # in code> i -  is to return the current value of  i  (i.e., the value is before the decrease) and then a <<> code   
 
 
 
 So, we need to convert him to VB. We can not use  i - = 1  because it does not return the current value of  i  before it decreases. Therefore, we need an operation that reduces  i , but the value of  i  comes back to the value, like something: 
 
  Function DoPostDecrement (I as integer) ByRef integer as I - = 1 return i + 1 termination function  
 
 But to write a method to perform this To avoid being suggested to use the following: 
 
  System.Math.Max ​​(someValueThatIsEqualToiMinusOne, someValueThatIsEqualtoiBeforeTheDecrement)  
 
 but V B.NET will not use you to replace  me - = 1  or  i = i - 1  in the  some valueIsquateTimionOn . However,  System.Threading.Interlocked.Decrement (i)  is valid and the value of  i-1  is equal. Once you have done that, because the parameter is correct, the  someValueThatIsEqualtoiBeforeTheDecrement  is left to be evaluated to  i + 1  (execute on that point decreasing  i + 1  is the decreasing value. 
 
 Note that the above method is  DoPostDecrement  and  System.Math.Max, System. Threading.Interlocked.Decrement  creation can be different semantically in a multi-reference context.