Solved

c# generic syntax don't understand

Posted on 2015-02-03
6
171 Views
Last Modified: 2015-02-03
Can anyone explain this to me...I'm too dumb! This is from the telerik mvc grid extensions, you make columns with
Grid.Columns(columns=>{
columns.Bound("xx");etc
}
I put a break in the Columns func, and its sig is:
Columns(Action<GridColumnFactory> configurator)
Now, I understand, Action<T> is a delegate void method, but what I don't understand is how columns=>{
columns.Bound("xx"); }is implicitly cast to GridColumnFactory?
(GridColumnFactory- a class which has params in its constructor )
0
Comment
Question by:Silas2
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 3
6 Comments
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 40586143
It isn't being implicitly cast - it is explicitly declared by the Columns() method.

If you look at the documentation for the Columns() method, you'll see that it takes a parameter of type Action<GridColumnFactory<T>> (reference: http://www.telerik.com/help/aspnet-mvc/m_telerik_web_mvc_ui_fluent_gridbuilder_1_columns.html) where T is the model that the grid is being bound to.
0
 

Author Comment

by:Silas2
ID: 40586297
Ok, its in the function sig in the docs, but how does columns=>{ columns.bound("xx"; columns.bound("yy");} become acceptable as GridColumnFactory? it doesn't look anything like the factory.
0
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 40586454
columns (the left-hand operator version) is created at runtime implicitly based on the context.  The runtime can figure out the type from the context.

So, in you case, columns will actually be an object of type GridColumnFactory<TModel>. Bound() is a method on the factory class.

Hope that makes some sense.
0
PeopleSoft Has Never Been Easier

PeopleSoft Adoption Made Smooth & Simple!

On-The-Job Training Is made Intuitive & Easy With WalkMe's On-Screen Guidance Tool.  Claim Your Free WalkMe Account Now

 

Author Comment

by:Silas2
ID: 40586630
Most kind, yes Its certainly helping.

So when the param comes into the call it (the runtime) hasn't instanced the factory even though it's (or something is) in the call.

In the call , (which is on the GridBuilder obj), this is the first line:
configurator(new GridColumnFactory(Component, Context));

(configurator is the method param)

Aah, the penny (half) dropped as I was typing, so the configurator is an Action<GridColumnFactory<T>>, does that mean the default call is to make a new one? Factory I mean, so does that mean if x = Action<Type>, then x(new Type())?
0
 
LVL 52

Accepted Solution

by:
Carl Tawn earned 500 total points
ID: 40586671
>> so the configurator is an Action<GridColumnFactory<T>>, does that mean the default call is to make a new one?

Yes, that's the jist of it.  Because it is a Lambda expression, the underlying mechanics will instantiate a new object of type Action<GridColumnFactory<T>>, and that becomes the context for the expression.  So, anything to the right of => is using an instance of the GridColumnFactory<T> object to make calls on.
0
 

Author Comment

by:Silas2
ID: 40586769
So, from the docs:
Action<string> messageTarget;
messageTarget = s => Console.WriteLine(s);

So with the grid:
Action<GridColumnFactory<T>> x;
x=>{ x.Bound(1); x.Bound(2); }

Ah, I think I get it, for each x.Bound call, its using the factory's bound call. So the call into 'Columns', is receiving the right param, not because its been explicitly sent, but because the receiving procedure but because of its signature.
0

Featured Post

Salesforce Made Easy to Use

On-screen guidance at the moment of need enables you & your employees to focus on the core, you can now boost your adoption rates swiftly and simply with one easy tool.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article introduced a TextBox that supports transparent background.   Introduction TextBox is the most widely used control component in GUI design. Most GUI controls do not support transparent background and more or less do not have the…
Performance in games development is paramount: every microsecond counts to be able to do everything in less than 33ms (aiming at 16ms). C# foreach statement is one of the worst performance killers, and here I explain why.
In this video we outline the Physical Segments view of NetCrunch network monitor. By following this brief how-to video, you will be able to learn how NetCrunch visualizes your network, how granular is the information collected, as well as where to f…
If you’ve ever visited a web page and noticed a cool font that you really liked the look of, but couldn’t figure out which font it was so that you could use it for your own work, then this video is for you! In this Micro Tutorial, you'll learn yo…

724 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question