1. Mårten Rånge
@marten_range

2. Model driven MetaProgramming
Using Visual Studio & T4

3. Let’s talk about code

4. DNRY
Do Not Repeat Yourself

5. Repeating myself
[Serializable]
public class AnException : Exception
{
public AnException ();
public AnException (string message);
public AnException (string message, Exception exc);
protected AnException (
SerializationInfo info, StreamingContext context);
[SecurityPermission(
SecurityAction.Demand, SerializationFormatter = true)]
public override void GetObjectData (
SerializationInfo info, StreamingContext context)
}

6. Repeating myself
AnException
Exception

7. Repeating myself
[Serializable]
public class AnException : Exception
{
public AnException ();
public AnException (string message);
public AnException (string message, Exception exc);
protected AnException (
SerializationInfo info, StreamingContext context);
[SecurityPermission(
SecurityAction.Demand, SerializationFormatter = true)]
public override void GetObjectData (
SerializationInfo info, StreamingContext context)
}

8. Repeating myself
public class MyViewModel : INotifyPropertyChanged
{
public int MyProperty
{
get { return m_myProperty; }
set
{
m_myProperty = value
OnRaisePropertyChanged ("MyProperty")
}
}
void OnRaisePropertyChanged (string propertyName);
}

9. Repeating myself
int MyProperty

10. Repeating myself
public class MyViewModel : INotifyPropertyChanged
{
public int MyProperty
{
get { return m_myProperty; }
set
{
m_myProperty = value
OnRaisePropertyChanged ("MyProperty")
}
}
void OnRaisePropertyChanged (string propertyName);
}

11. Repeating myself
public static readonly DependencyProperty PreviewWidthProperty =
DependencyProperty.Register (
"PreviewWidth",
typeof (double),
typeof (AccordionPanel),
new FrameworkPropertyMetadata (32.0));
public double PreviewWidth
{
get { return (double)GetValue (PreviewWidthProperty); }
set { if (PreviewWidth != value)
SetValue (PreviewWidthProperty, value); }
}

12. Repeating myself
double PreviewWidth

13. Repeating myself
public static readonly DependencyProperty PreviewWidthProperty =
DependencyProperty.Register (
"PreviewWidth",
typeof (double),
typeof (AccordionPanel),
new FrameworkPropertyMetadata (32.0));
public double PreviewWidth
{
get { return (double)GetValue (PreviewWidthProperty); }
set { if (PreviewWidth != value)
SetValue (PreviewWidthProperty, value); }
}

14. Deliver maximum business value for minimal cost

15. Code redundancy increase cost
Longer development times
Inconsistent behavior
Costlier maintenance
Stops us from doing the right thing

16. Tools to reduce redundancy
Loops
Methods
Polymorphism
Generics
Higher-order functions

17. Sometimes they don’t help

18. MetaProgramming

19. MetaProgramming is code that codes

20. T4 is MetaProgramming

21. Demo.001
Getting started with T4

22. T4 – ASP/PHP for code
class X
{
<# for (var iter = 0; iter < 10; ++iter) { #>
public int X<#=iter#> = <#=iter#>;
<# } #>
}

23. Exceptions revisited
[Serializable]
public class AnException : Exception
{
public AnException ();
public AnException (string message);
public AnException (string message, Exception exc);
protected AnException (
SerializationInfo info, StreamingContext context);
[SecurityPermission(
SecurityAction.Demand, SerializationFormatter = true)]
public override void GetObjectData (
SerializationInfo info, StreamingContext context)
}

24. Exceptions revisited
Exception sample from
“The CORRECT Way to Code a Custom Exception Class”
bit.ly/10TzZAh
@dseelinger

25. Exceptions revisited
C# lacks constructor forwarding
A weakness in the language

26. Demo.002
Generating exception classes

27. Exceptions revisited
MetaProgramming can combat code redundancy
caused by weaknesses in the language

28. Autobiographical examples
MC68000 – Self modifying code
C/C++
- Higher order macros
C++ - Partial template specialization
.NET
– System.Reflection.Emit
.NET
– System.Linq.Expressions
T-SQL
– SELECT * FROM SYS.tables
Visual Studio – T4

29. Benefits of T4
Simple concept
ASP/PHP for code
Easy to debug
The generated code can be debugged just as easy as hand
written code
Flexible
T4 can generate any text artifact
C#
VB
C++
Doesn’t affect deployment

30. Additional resources
Visual Studio Pro
2008, 2010 or 2012
T4 Addin
http://t4-editor.tangible-engineering.com/
Good T4 Blog
http://www.olegsych.com/

31. Best practices
The rule of two

32. Separate model & template

33. Separate generated & crafted code
partial class X
{
partial void Partial_Y (int q, ref int a);
public int Y (int q)
{
var a = 0;
Partial_Y(q, ref a);
return a;
}
}

34. Demo.003
Generating Dependency Properties with T4

35. DependencyProperties (WPF)
Controls requires DependencyProperties
DependencyProperty pattern  Redundant code
Becomes inconsistent
Error prone
Naming conventions
Takes a long time to write
Is mind-numbingly boring to write
T4 can help

36. T4 – ASP/PHP for code
class X
{
<# for (var iter = 0; iter < 10; ++iter) { #>
public int X<#=iter#> = <#=iter#>;
<# } #>
}

37. T4 saved me
MetaProgramming for me
Saves time
Improves quality
Puts the fun back into (meta)programming

38. Mårten Rånge
@marten_range