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sitebuilderLuc Pattyn25-Jan-22 14:34 
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QuestionC# EPPlus How to hide range of columns Pin
Mou_kol24-Jan-22 2:01
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AnswerRe: C# EPPlus How to hide range of columns Pin
Richard Deeming24-Jan-22 2:58
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AnswerRe: C# EPPlus How to hide range of columns Pin
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QuestionHow would you describe what an IEnumerable is to a bright student of C# Pin
BillWoodruff22-Jan-22 2:34
mveBillWoodruff22-Jan-22 2:34 
AnswerRe: How would you describe what an IEnumerable is to a bright student of C# Pin
jschell23-Jan-22 7:25
Memberjschell23-Jan-22 7:25 
So in terms of teaching...

BillWoodruff wrote:
What's so useful about deferred evaluation ?


The data returned is in memory.
Your computer has 32 gig of memory (or whatever it is.)
The IEnumerable returns 32 gig number of entries.
Where does it fit into memory if you did it all at once?

(Of course not saying that would be a good idea, but rather as a thought experiment.)


BillWoodruff wrote:
Why can't I test an IEnumerable to see if it's empty, or null; why do I have to trigger iteration with 'Count() to see how many items it has, and, why can I only use 'Any to see if there are no items in it without triggering iteration..


The interface can only do what the interface does. This specific interface is very old and was only designed, very likely, with in memory arrays/lists in mind. Enhancing it now would break everything.

Might want to mention there are other ways to do it that would allow one to do that even for large sets (so not bringing everything into memory.) But also mention that using linq to process large sets in memory is going to be a problem regardless.


BillWoodruff wrote:
Isn't deferred evaluation dangerous because you have no idea of what might have changed in the time between assembling the IEnumerable and iterating/evaluating it ?


What if you have the set in memory and the source changes between when you use it and then? How is that not the same problem? There is no such thing as absolute anything in the universe including time. So understand the problem and define the rules to deal with the differences that will occur. Example is ordering something online but while you are ordering something else the first item gets all used up by other people's orders. So when you finally go to pay it tells you it out of stock. When you started it was there but by the time it was needed it was gone.
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
Richard Deeming23-Jan-22 21:59
mveRichard Deeming23-Jan-22 21:59 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
BillWoodruff25-Jan-22 3:23
mveBillWoodruff25-Jan-22 3:23 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
jschell30-Jan-22 6:37
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AnswerRe: How would you describe what an IEnumerable is to a bright student of C# Pin
#realJSOP24-Jan-22 23:44
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AnswerRe: How would you describe what an IEnumerable is to a bright student of C# Pin
endo funk26-Jan-22 5:31
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GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
Gerry Schmitz26-Jan-22 6:13
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GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
endo funk26-Jan-22 9:40
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GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
Gerry Schmitz27-Jan-22 16:58
mveGerry Schmitz27-Jan-22 16:58 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
endo funk27-Jan-22 19:35
Memberendo funk27-Jan-22 19:35 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
Gerry Schmitz28-Jan-22 5:50
mveGerry Schmitz28-Jan-22 5:50 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
endo funk28-Jan-22 6:40
Memberendo funk28-Jan-22 6:40 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
Gerry Schmitz28-Jan-22 7:29
mveGerry Schmitz28-Jan-22 7:29 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
endo funk28-Jan-22 8:46
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GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
BillWoodruff26-Jan-22 23:52
mveBillWoodruff26-Jan-22 23:52 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
BillWoodruff26-Jan-22 23:39
mveBillWoodruff26-Jan-22 23:39 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
endo funk27-Jan-22 6:44
Memberendo funk27-Jan-22 6:44 
GeneralRe: How would you describe what an IEnumerable is to a bright student of C# Pin
BillWoodruff27-Jan-22 23:44
mveBillWoodruff27-Jan-22 23:44 

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