ECMA-334 C# Language Specification

25.5.3: Pointer element access

A pointer-element-access consists of a primary-no-array-creation-expression followed by an expression enclosed in "[" and "]".

pointer-element-access
primary-no-array-creation-expression [ expression ]

In a pointer element access of the form P[E], P must be an expression of a pointer type other than void*, and E must be an expression of a type that can be implicitly converted to int , uint , long , or ulong .

A pointer element access of the form P[E] is evaluated exactly as *(P + E). For a description of the pointer indirection operator (*), see 25.5.1. For a description of the pointer addition operator (+), see 25.5.6.

[Example: In the example 
class Test  
{  
   static void Main() {  
      unsafe {  
         char* p = stackalloc char[256];  
         for (int i = 0; i < 256; i++) p[i] = (char)i;  
      }  
   }  
}
a pointer element access is used to initialize the character buffer in a for loop. Because the operation P[E] is precisely equivalent to *(P + E), the example could equally well have been written: 
class Test  
{  
   static void Main() {  
      unsafe {  
         char* p = stackalloc char[256];  
         for (int i = 0; i < 256; i++) *(p + i) = (char)i;  
      }  
   }  
}
end example]

The pointer element access operator does not check for out-of-bounds errors and the behavior when accessing an out-of-bounds element is undefined. [Note: This is the same as C and C++. end note]