Application Modernization: What Is It and How to Get Started
I want you to know that your illustrious executive editor, Brad Jones, is looking out for you. I proposed this article in my quarterly column calendar and Brad asked me if this was going to be a drag-and-drop article. I answered: No.
His question illustrated why I wanted to write this article. Current versions of Visual Studio.NET support snippets—simply drag and drop some code into the toolbox and you can reuse it anytime you'd like. While useful, this function is not very exciting and it's often overlooked. Code snippets in Visual Studio 2005, however, are far more useful and deserve your attention. Based on XML, they support replaceable parameters, allow inserting assembly references and imports statements, and enable better organization. They also let you share management with other developers easily.
This article is my meager effort to encourage you to take advantage of code snippets. It briefly demonstrates how to create a snippet in Visual Studio 2005 beta 2 using XML.
Half-Baked Beta Bumps
Beta means not quite finished. Think of beta applications as muffins pulled out of the oven before they are baked. Glaringly missing from the VS 2005 beta 2 is a code snippet editor. The official public statement is that the code snippet editor isn't quite ready for users. While waiting for the final release of VS 2005, you can download an external code snippet editor that comes complete with source code from MSDN. The examples in this article use this sample VB code snippet editor, which you can use until VS 2005 ships with its built-in editor.
What Are Code Snippets?
A code snippet is exactly what it sounds like: a small piece of code. Like project templates and project item templates, code snippets are discrete chunks of written code. Also, like templates, code snippets support replaceable parameters, which permit you to customize a snippet for each context.
If you need whole projects or project items, you can use templates. For something smaller or just to show the code in IntelliSense and make it pluggable, use code snippets.
Create a Code SnippetCode snippets are stored as XML in a file with a .snippet extension. Like all XML, these code snippet files have a specific format. Additionally, the snippet files need to be placed where Visual Studio can locate them. To this end, the snippet manager—which the final section covers—makes it easy to organize snippets.
XML, being based on SGML (Standard Generalized Markup Language), is an elegant concept but an ugly language that isn't very human friendly. However, it is very useful in the Internet age because its text, its extensibility, and its predictable format-simply identify an opening tag and then fill in the blanks between the opening and closing tags. (Almost every tag has a symmetric closing tag with the same name and an additional forward slash (/).)
Snippets support tags for replaceable elements, but the simplest snippets—those that contain literal code with no parameters—just need the code you want to insert. This code is an attribute of the <Code> tag. Listing 1 contains a simple Hello, World! snippet. To create additional snippets, copy and paste the literal code in the [CDATA] attribute with the new snippet code.
Listing 1: XML for a Literal Snippet
<?xml version="1.0"?> <CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/ 2005/CodeSnippet"> <CodeSnippet Format="1.0.0"> <Header> <Title>Canonical Hello, World! example</Title> </Header> <Snippet> <Code Language="VB"><![CDATA[MsgBox("Hello, World!")]]></Code> </Snippet> </CodeSnippet> </CodeSnippets>
Add Imports and References
You add imports and references after the <Snippet> tag. If you want to add an assembly reference, add a <Reference> tag with a nested <Assembly> tag followed by the name of the assembly (see Listing 2). Add <Import><Namespace> tags after the <Reference> tag. The <Imports> tag adds imports statements to the same module that you added the snippet to.
The excerpt in Listing 2 shows how to reference the System.Data.dll assembly and add an imports statement for the System.Collections namespace.
Listing 2: Elided Excerpt from a Snippet File Showing the Tags for an Assembly Reference and a Namespace Imports Statement
<?xml version="1.0"?> <CodeSnippets xmlns="http://schemas.microsoft.com/VisualStudio/ 2005/CodeSnippet"> <CodeSnippet Format="1.0.0"> <Header> <Title /> </Header> <Snippet> <References> <Reference> <Assembly>System.dll</Assembly> </Reference> </References> <Imports> <Import> <Namespace>System.Collections</Namespace> </Import> </Imports> <Declarations> ...
Add Literal and Object Replacements
Replacements represent elements of your snippet that the user has to provide. To identify a replacement, add a <Declarations> tag at the same level as the <References> and <Imports> tags. If the replacement is a literal, add a <Literal> nested tag; for objects, add an <Object> nested tag. Both literal and object tags include <ID>, <ToolTip>, and <Default> child tags, and the object tag has an extra <Type> child tag that indicates the type of the object.