X++, C# Comparison: Precompiler Directives

[アーティクル]
05/18/2015

Applies To: Microsoft Dynamics AX 2012 R3, Microsoft Dynamics AX 2012 R2, Microsoft Dynamics AX 2012 Feature Pack, Microsoft Dynamics AX 2012

X++ and C# share some keywords for their precompiler directive syntax, but the meanings are not always the same.

X++ to C# Comparisons

The following sections describe the similarities and differences between the precompiler directives used in X++ and C#.

Similarities

The X++ and C# compilers recognize many of the same keywords. In most cases, the keywords mean the same for both language compilers.

Differences

A fundamental difference between the precompiler directives in X++ versus C# is the #define keyword that both language precompilers recognize. Unlike C#, in X++ the #define directive requires a dot in its syntax. In X++, parentheses can be used to give the defined symbol a value. These differences are shown in the following examples:

In X++: #define.InitialYear(2003)
In C#: #define InitialYear

A minor difference is that in C# there can be spaces and tab characters between the # character and the directive keyword, such as # define Testing.

Comparison Tables

The following tables compare the details of precompiler directives between X++ and C#.

Identical Keywords

The following table lists precompiler directives that are similar in X++ and C#.

Keyword	X++	C#	Comments
#define	In X++, a precompiler variable name can be defined, and a value can be given to that variable.	In C#, a precompiler variable name can be defined, but no value can be given to that variable. Also, any #define in C# must occur at the top of the file, and cannot occur after any code such as a using statement or a class declaration.	The C# compiler can input a command line parameter of /define to define a precompiler variable name without defining the variable in any C# code file. The X++ compiler has no counterpart to /define.
#if	In X++, #if can determine whether a precompiler variable exists, and whether the variable has a given value.	In C#, #if can only determine whether a precompiler variable exists. It cannot test for any value because no value can be assigned.
#endif	In X++, #endif marks the end of an #if block. It also ends an #ifnot block.	In C#, #endif marks the end of an #if block, regardless of whether the block includes a #else.

Different Keywords with the Same Processing Result

The following table lists precompiler directives that are named differently in X++ and C#, but that give the same results when processed.

X++	C#	Comments
#ifnot	#if #else	There is no #else directive in X++, but the #ifnot provides similar functionality. In X++, #ifnot can determine whether a precompiler variable exists, and whether the variable does not have a specific given value. In C#, #if can determine whether a precompiler variable exists when the ‘!’ symbol is prefixed to the variable name.
//BP Deviation documented	#pragma warning	These X++ and C# entries are not equivalent, but there is a partial similarity. Both suppress compiler warning messages.
#macrolib	.HPP file in C++	There is a partial similarity between the X++ directive #macrolib versus an .HPP file in C++. Both can contain several #define statements.

#ifnot

#if

#else

There is no #else directive in X++, but the #ifnot provides similar functionality. In X++, #ifnot can determine whether a precompiler variable exists, and whether the variable does not have a specific given value.

In C#, #if can determine whether a precompiler variable exists when the ‘!’ symbol is prefixed to the variable name.

//BP Deviation documented

#pragma warning

These X++ and C# entries are not equivalent, but there is a partial similarity. Both suppress compiler warning messages.

#macrolib

.HPP file in C++

There is a partial similarity between the X++ directive #macrolib versus an .HPP file in C++. Both can contain several #define statements.

Precompiler Directives Exclusive to X++

The following table lists X++ precompiler directives that have no direct counterpart in C#.

X++	Comments
#linenumber	The #linenumber directive is for obtaining the line number, so that it can be output to the Infolog. The C# directive #line is different because its purpose is for setting the line number.
#defdec #definc
#globaldefine	In X++, there is a small difference between #globaldefine versus #define. The difference is that #globaldefine never overwrites a current nonnull value that was assigned to a precompiler variable by #define. C# has nothing similar to this difference, because in C#, a precompiler variable name cannot be given a value.
#localmacro #macro	In X++, #localmacro enables you to assign a multiline value to a precompiler variable. #macro is a synonym, but #localmacro is recommended. In C#, the #define directive has part of this functionality, but it cannot assign a value to a precompiler variable.
#globalmacro	In X++, #globalmacro is almost the same as the preferred #localmacro.

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