c# - Consume Extension method in non-static class -

all of examples extension methods have seen consume extension method in class like:

class program {     static void main()     {         ...call extension method here     } } 

these seem work because consuming class static. there way consume extension method in non static class below? can't seem find examples this.

i have extension method class:

using system; using system.collections.generic;  namespace awesomeapp {     public static class linqextensionmethods     {         public static ienumerable<t> finditemsbeforeandafter<t>(this ienumerable<t> items, predicate<t> matchfilling)         {             if (items == null)                 throw new argumentnullexception("items");             if (matchfilling == null)                 throw new argumentnullexception("matchfilling");             return items;         }     } } 

and have class consumes extention method

namespace awesomeapp {     public class leaders : ileaders     {         var leaders = getallleaders();          var orderedleaders = leaders.orderbydescending(o => o.pointsearned);          var test = orderedleaders.finditemsbeforeandafter(w => w.userid == 1);     } } 

if call extension method static class not the 'extension method must defined in non-generic static class' error:

public class test {     public void testfunc()     {         list<int> testlist = new list<int>() {1,2,3,4,5,6,7,8,9};          testlist.finditemsbeforeandafter<int>(e => e == 5);      } } 

i have read through stackoverflow answers can find on non-generic static class error , deal writing extension method don't deal consuming it.

so question is: if using extension method non-static class not possible there way works in similar way? example can called .extensionmethod not helper.extensionmethod(passedobject)??

resolution: thought cut , pasted extension method public class leaders : ileaders own class make static copied it. compiler error pointing class name did not see extension method still @ bottom of file. error message accurate , answered correct.

these seem work because consuming class static.

no, that's incorrect. extension methods don't have consumed static classes or static methods.

however, have declared in class is:

• non-nested
• non-generic
• static

you appear confusing calling declaring - when say:

if call extension method static class not the 'extension method must defined in non-generic static class' error

... you'll if try declare method in class doesn't satisfy above criteria. should double click on error show it's being generated - i'm sure you'll find it's declaration, not use of method.

note final example (class test) not static class, nor static method.