Code that Codes For You

Using T4 Templates to improve your code's maintainability, and editing the default Entity Framework T4 templates
Demo Code at http://goforth.codeplex.com/SourceControl/latest

Transcript

1. Code that Codes For You (T4 Templates) A basic intro to T4 templates and how you can use them in your projects now to save you time. Richard Goforth RichardGo@Magenic.com Contact Magenic 1600 Utica Avenue South, Suite 800 St. Louis Park, MN 55416 1 (877)-277-1044 info@magenic.com
2. What Are T4 Templates » Text Template Transformation Toolkit » Text blocks with control logic (similar to programming for the web) » Regular code, a small isolated program with a very specific purpose » Any input and any output (you can do anything you want, though it is not necessarily wise).
3. Why Use T4 Templates » DRY – Don’t Repeat Yourself » The ability to repeat yourself less often then before » More places with single location maintenance than you were able to do without T4 » Reduce manual mistakes and omissions in syncing code changes across different types of files and databases
4. T4 Template Process
5. Some Usage Scenarios Field Level Sync •Config Files External System Continuity •DB Enumeration Classes and Enums in Code •ASPX Navigation with Intellisense and compiler support Highly Repeatable Code •Data Entity Classes •WiX File Creation •CRUD Stored Procedures
6. Using T4 in Visual Studio Tools -> Extension Manager -> Online Templates -> Search » Tangible T4 Editor » Syntax highlighting » IntelliSense in code blocks » T4 Toolbox » Includes several basic templates to get you started on a number of different tasks
7. Basic Structure Basic Control Structure Usually Surround Text blocks (use {}) Loops and Decision Trees <# Inline Evaluation Used for a substituting a single field or value Use anything in the current scope <#= Class Function Location doesn’t matter Class blocks that sit next to the generating class <#+ Directive Statement Define output, imports, and include statements New in VS2010: template parameters <#@
8. Basic Structure <#@ template debug="true" hostSpecific="true" language="C#" #> <#@ output extension=".cs" #> <#= System.DateTime.Now.ToString() #> //Comment at the top of the file <# foreach(var prop in getProperties()) { WriteLine(prop.key); } #> <#+ public Dictionary<Type, string> getProperties() { … } #>
9. Built in Functions All of these are methods on the TextTransformation class » Write / WriteLine » Text blocks are converted to “Write” statements on preprocessing » PushIndent / PopIndent /ClearIndent » Use these with a string argument to set the indent to that string. » Warning » Will output a Visual Studio warning upon compiling the template » Error » Catch Exceptions in your template and use the error method to output for a better debugging experience
10. Demo 1 – A basic template
11. Common Inputs XML UML Diagrams WSDL Anything else you can think of Edmx Model First EF Uses Microsoft Libraries to deal with the edmx file SQL Database Enums in a DB First Environment CRUD Stored Proc Generation Linq To Sql Code from an existing DB
12. Template Include Files » Directive » <#@ include file=“filename.ttinclude” #> » Helper Function Libraries » Surrounded with <#+ #>, the class indicator
13. Demo 2 – XML Input with include file
14. Creating Multiple Files » Two similar file management classes » T4 Template Manager class by Damien Guard » http://damieng.com/blog/2009/11/06/multiple-outputs-from-t4- made-easy-revisited » The EF Way » EntityFrameworkTemplateFileManager in EF.Utility.CS.ttinclude
15. Modifying EF DB Generation Code » Example – Having the defaults defined in the Model output as part of the db script. » SSDLToSQL10.tt » Add a call to a new method (WriteDefault()) to output the default value for a property in the edmx file to the sql output » GenerateTSQL.Utility.ttinclude » Create the write default method that takes the EDMProperty and extracts the appropriate sql text for a default value
16. Modifying EF Class Generation Code » Model.tt example – an extra method on each class » I wanted to take the dictionary created from Telerik controls and populate values on my generated classes directly from them. » I wanted to set associated navigation properties as well » SetPropertiesFromDictionary()
17. Demo 3 Editing EF Generation Files
18. Simple Debugging » <#@ template debug="true" language="C#" #> » <#@ import namespace="System.Diagnostics" #> » <# Debugger.Launch(); #> » Added at the beginning of your code, this will prompt you to open a new instance of VS and debug the template generation » <# Debugger.Break(); #> » re-enter the debugger later in the code
19. T4 Toolbox Script File Generator Run code whenever a file in the project is changed Update dependent files Validate an xml file against a schema
20. Demo – XML Schema Validation on Save
21. Preprocessed (Design-Time) Templates » TextTemplatingFilePreprocessor » TextTemplatingFileGenerator » Outputs a cs file that can be run with Template.Transform, so that templates can be created within another program, or with runtime context
22. Newness » In 2012 » Improvements in debugging, the templates don’t have to run in the devenv process, and thus can be debugged directly. » “PreProcessed” is now “Design-Time” » In 2010 » Template inheritance » Parameters » In Tangible T4 Editor 2.0 » Transform on Build
23. Places to Visit » http://www.olegsych.com/ » MSDN T4 Pages » http://www.youtube.com/playlist?list=PL6D51E9F1B9C955BB » http://t4-editor.tangible-engineering.com/t4_editor_Videos.html » RichardGo@magenic.com
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