# IT:AD:Transformations:T4:HowTo:Create a Code File #



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## Process ##

After starting a new page

### Includes ###

Use [[IT/AD/T4/Syntax/Directives/]] to include what you need:

    <#@ include file=”T4Toolbox.tt” #>


### C# Namespaces ###

Use [[IT/AD/T4/Syntax/CodeBlocks/]] Create the namespace:

    namespace <#=codeGenerationTools.EscapeNamespace(namespaceName)#>
    {
    //Code goes here:
    }


#### Outputing Collapsible Regions ####

Single File T4 code quickly become unwieldy, multiple T4 files even worse. 
THerefore, whereas collapsible code sections in C# is a AntiPattern, collapsible code in T4 scripts is helpful.

    <#
    CodeRegion codeRegion = new CodeRegion(this, 1);
    ...
    region.Begin("Primitive Properties");
    #>
    
    //Your code here
    
    <#
    codeRegion.End();  //Or ClearIndent();
    #>

>Note:The region will not be generated if no source code is generated for the region.


## Outputing Code Indentation ##

Regions are ok...but what really makes code readable are indents/outdents...

    <#
    PushIndent(”\t”); //or ”\t\t” or "  "
    #>
     
    //Blah...
    
    <#
    PopIndent();
    #>



## TextTransformation Class ##

What do you mean `PushIndent`/`PopIndent`?!? Where did those method definitions come from?! Who the heck defined those methods?!?

Turns out the while you are in the *.tt file, you are in the context of a class -- the `TextTransformation` class. 

So, since you are in the context, anywhere in the page gives you access to a couple of other methods worth knowing about (links point to MSDN documentation pages):

* [ClearIndent](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.clearindent.aspx): Resets the [CurrentIndent](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.currentindent.aspx) to an empty string.
* [Error](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.error.aspx): Creates a new error to store information about errors that occur during the text template transformation process.
* [Initialize](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.initialize.aspx): Infrastructure. Initializes the TextTransformation class.
* [PopIndent](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.popindent.aspx): Removes the most recently added text from CurrentIndent.
* [PushIndent](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.pushindent.aspx): Adds text to CurrentIndent, which is prefixed to each line of the generated text output.
* [TransformText](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.transformtext.aspx): When overridden in a derived class, generates the text output of the transformation.
* [Warning](http://msdn.microsoft.com/en-us/library/microsoft.visualstudio.texttemplating.texttransformation.warning.aspx):Creates a new warning to store information about errors that occur during the text template transformation process.
* [Write(String)](http://msdn.microsoft.com/en-us/library/bb126394.aspx):Appends a copy of the specified string to the generated text output.
* [Write(String,Object())](http://msdn.microsoft.com/en-us/library/bb126395.aspx):  equivalent of regex StringFormat...
* [WriteLine(String)](http://msdn.microsoft.com/en-us/library/bb126392.aspx): Appends a copy of the specified string and the default line terminator to the generated text output.
* [WriteLine(String,Object())](http://msdn.microsoft.com/en-us/library/bb126393.aspx): equivalent of StringFormat

>The most commonly used will be WriteLine and the indent/output.   
[http://msdn.microsoft.com/en-us/library/bb126474.aspx](http://msdn.microsoft.com/en-us/library/bb126474.aspx)

 

## Access to Host Environment (i.e. Visual Studio) ##

If we lived in a bubble...But we don't.

So we need to know how to get in touch with the world outside of our template...

    EnvDTE.DTE dte = (EnvDTE.DTE) ((IServiceProvider) this.Host)
                       .GetService(typeof(EnvDTE.DTE));

Src: [http://msdn.microsoft.com/en-us/library/bb126474.aspx](http://msdn.microsoft.com/en-us/library/bb126474.aspx)



## Getting the Current Namespace ##

A perfectly good example of why we need to ask questions outside of our template is to inquire as to the project's default namespace:

    <#
    // Get the project's default namespace:
    IServiceProvider serviceProvider = (IServiceProvider)Host;
    DTE dte = (DTE)serviceProvider.GetService(typeof(DTE));

    ProjectItem templateItem = dte.Solution.FindProjectItem(Host.TemplateFile);
    #>
    namespace <#= templateItem.ContainingProject.Properties.Item("DefaultNamespace").Value #>.SomeSubNSOfYours {
    //...
    }

 

## Standard Helper Classes ##

Are there any other methods we can use, other than what was available in the `TextTransformation` class?

Sure...just include the standard template that is used by all of the EF4 templates:

    <#@ include file="EF.Utility.CS.ttinclude"#>

It's a single file that contains several classes of ready helper methods.

> See here for the full list of methods you may find useful:     [[IT/AD/T4/Syntax/ttinclude/]]