Variable Identifiers

Keywords may be used as identifiers if they include “@” as a prefix (E.g. @return).
There are four undocumented reserved keywords which are required only in rare interop scenarios: __arglist, __makeref, __reftype, and __refvalue.

Hexadecimal Notation

To specify a hexadecimal value, prefix the value with “0x” and then use any hexadecimal digit.
- E.g. 0x000A corresponds to the decimal value 10 and 0x002A corresponds to the decimal value 42.
- Each hex digit is four bits, so a byte can represent two hex digits.

int integralValue = 0x000A;
string hexValue = integralValue.ToString("X");

It can sometimes be necessary to reference two versions of assemblies that have the same fully-qualified type names.
- For example, when you need to use two or more versions of an assembly in the same application.
By using an external assembly alias, the namespaces from each assembly can be wrapped inside root-level namespaces named by the alias.
To reference two assemblies with the same fully-qualified type names, an alias must be specified at a command prompt, as follows:

/r:GridV1=grid.dll
/r:GridV2=grid20.dll

This creates the external aliases GridV1 and GridV2.
To use these aliases from within a program, reference them by using the **extern** keyword.

extern alias GridV1;
extern alias GridV2;

Each extern alias declaration introduces an additional root-level namespace that parallels (but does not lie within) the global namespace.
Thus types from each assembly can be referred to without ambiguity by using their fully qualified name, rooted in the appropriate namespace-alias.
In the previous example, GridV1::Grid would be the grid control from grid.dll, and GridV2::Grid would be the grid control from grid20.dll.