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Comments, using, and print statements

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This article describes statements in X++.

Comments

It's a good practice to add comments to your code. Comments make a program easier to read and understand. Comments are ignored when the program is compiled. Your comments can use either the // style or the /* style. However, a best practice is to use the // style for comments, and even for multiline comments.

// This is an example of a comment.
/* Here is another example of a comment. */

You use the print statement to output text through System.Diagnostics.WriteLine to the Visual Studio Output window. During testing, the print statement is an alternative to the Global::info method, which shows text in the Infolog window. The following table compares the print statement and the info method.

Feature print statement info method
Ease of invocation The print statement automatically converts various data types into strings. It can convert multiple data types in one invocation. The info method requires that the input parameter be a string.
Ability to copy contents to the clipboard Text is easily copied from the Output window to the clipboard. Text is easily copied from the Infolog window to the clipboard.
Typical usage The print statement is used for convenience during testing. It can help you debug small issues without having to run a formal debugger. The info method is appropriate for use in production.

Example of a print statement

The following code example demonstrates the print statement automatically converting any date type to a string. You do not need to prefix info with Global:: when you call it.

str hello = "Hello";
int fortytwo = 42;
utcDateTime now = DateTimeUtil::utcNow();
Dialog dialog = new Dialog();

print "The print statement automatically converts data types to strings.";
print hello, " -- ", fortytwo, " -- ", now, " -- ", dialog;
// Output to the Print window:
// The print statement automatically converts data types to strings.
// Hello -- 42 -- 10/3/2011 09:18:10 pm -- 1

// int2Str converter is needed when using info().
info("Hello");
info(int2Str(fortytwo));

// Output to Infolog window:
// Hello
// 42

TODO comments

The compiler recognizes the string TODO when it occurs at the start of a comment. The TODO string prompts the compiler to report the rest of the comment text in the Task List window in Microsoft Visual Studio. To open the Task List window, select View, and then select Task Window. The Task Window reports the line number where the TODO comment can be found in the code.

Here are the rules for using TODO in comments:

  • The TODO string can appear in a comment that uses either the // style or the /* style.
  • The TODO string must be the very first non–white space string in the comment. A carriage return, a line feed, a tab, and a space are all considered white space.
  • No white space is required between the start of the comment and the TODO.
  • The TODO string is case-insensitive. However, the convention is to type TODO in all uppercase letters, instead of ToDo or another variation.
  • The TODO string can have any characters appended to it. However, the convention is either to append a colon to the TODO string or to follow it with a white space.
  • The rest of the comment after the TODO string is reported as the task description. If the comment is longer than 200 characters, it might appear truncated on the Tasks tab.
  • The TODO task description can be spread over multiple lines when the /* comment style is used.

Examples of TODO comments

The following examples show TODO comments.

// An example of using TODO in the // style of comment.
public boolean isLate()
{
    // TODO: Finish this stub.
    return true;
}

// An example of using TODO in the /* */ style of comment.
public boolean isLate()
{
    /* TODO Finish this stub */
    return true;
}

Unsupported statements: changeSite, pause, and window

The changeSite, pause, and window keywords are no longer a part of the X++ language. These keywords will cause compilation errors if you use them.

Ignored statements: server and client

In previous versions (AX2012 and earlier), you could designate a method to run on either the client or the server. This is no longer possible, because all X++ code is executed as .NET CIL on the server. The keywords client and server are ignored. Their use doesn't cause a compile error, but they should not be used in any new X++ code.

using clauses

You use using clauses so that you don't have to provide the fully qualified name of a type. The using clause must precede the class that it applies, and it's required in every source file that you want it to apply to. Typically, all using clauses are put at the beginning of the source file. You can also provide aliases that introduce a short name for a fully qualified name. Aliases can denote namespaces or classes.

The following example shows a using clause, a namespace alias, and a class alias.

using System;
using IONS=System.IO; // Namespace alias
using Alist=System.Collections.ArrayList; // Class alias

class UsingClass
{
    public static void test()
    {
        Int32 I;                  // Alternative to System.Int32
        Alist al = new Alist();   // Using a class alias
        al.Add(1);
        str s = IONS.Path::ChangeExtension(@"c:\tmp\test.xml", ".txt"); // Using a namespace alias
    }
}

using statements

The using statement helps guarantee that objects that implement IDisposable are disposed of correctly. When you use an IDisposable object, you should declare and instantiate it in a using statement. The using statement calls the Dispose method on the object in the correct way, even if an exception occurs while you're calling methods on the object. You can achieve the same result by putting the object inside a try block and then explicitly calling Dispose in a finally block. The using statement simplifies the syntax and disposes of the object correctly. Here is the syntax for a using statement:

using ( expression ) { statement }

In this syntax, statement can be a block of statements, and expression declares and instantiates an object that implements IDisposable. The following example creates and uses a StreamReader object.

static void AnotherMethod()
{
    str textFromFile;
    using (System.IO.StreamReader sr = new System.IO.StreamReader("c:\\test.txt"))
    {
        textFromFile = sr.ReadToEnd();
    }
}