It’s code-generator tool which make possible to inject any type of the code.
Using
In any file (text or script) declare macros:
#region source macros MACROSNAME
var anyCode = 0;
++anyCode;
#endregion
In any file (where you want to use it):
#region macros MACROSNAME
#endregion
Result:
#region macros MACROSNAME
/* This code is auto-generated
* Do not change it
*/
var anyCode = 0;
++anyCode;
#endregion
So, you edit your code only once and it’s automatically updated in all your scripts.
Why
Try to imagine you have 2 base classes - Image and Text.
public class Image {
private Texture texture;
public void SetTexture(Texture texture) {
this.texture = texture;
}
public Texture GetTexture() {
return this.texture;
}
}
public class Text {
private string text;
public void SetText(string text) {
this.text = text;
}
public string GetText() {
return this.text;
}
}
So, now you want to create ImageAndText class:
public class ImageAndText {
// What do you want to place here? Hm...
}
To avoid of copy-paste your code you can use macros:
public class ImageAndText {
#region macros IMAGE
#endregion
#region macros TEXT
#endregion
}
And declare it in both Text and Image classes:
public class Image {
#region source macros IMAGE
private Texture texture;
public void SetTexture(Texture texture) {
this.texture = texture;
}
public Texture GetTexture() {
return this.texture;
}
#endregion
}
public class Text {
#region source macros TEXT
private string text;
public void SetText(string text) {
this.text = text;
}
public string GetText() {
return this.text;
}
#endregion
}
It’s looks like you can do this things:
public class ImageAndText : Image, Text {}
But you can’t do this in C#, so you can use this hack 
And yep, it’s free and open-source 
You can download it for free here: