iterator parameter in generics function C# -

i convertall generic function

public static iout convertall<iin, iout, t, toutput>(this iin source, converter<t, toutput> converter)         iin : ienumerable<t>         iout : ienumerable<toutput>     {         foreach (var item in source)             yield return converter(item);     } 

the problem visual studio tell me :

the body of 'sgd.collectionextensions.convertall(iin, system.converter)' cannot iterator block because 'iout' not iterator interface type

the things have clause should recognize iterator, isn't ?

i try :

public static i<toutput> convertall<i, t, toutput>(this i<t> source, converter<t, toutput> converter)         : ienumerable     {         foreach (var item in source)             yield return converter(item);     } 

but says

the type parameter 'i' cannot used type arguments

so don't know do. don't want function :

public static ienumerable<toutput> convertall<t, toutput>(this ienumerable<t> source, converter<t, toutput> converter)     {         foreach (var item in source)             yield return converter(item);     } 

it's simpler , it's working return ienumerable want same kind of iterator in output have in input

hope can me

so let's want output list. list<t> implements ienumerable<t>. defining creation of new list? defining how new item added list?

you aren't.

yield return means constructed class implement ienumerable<t> or ienumerator<t>. that's knows how construct. can accept input of other ienumerable<t>. accept input of list<t>, example. again, last function (the 1 don't like), don't need use earlier syntax functionality.

you add additional delegate parameters 2 operations need (or one, since can add generic constraint creation).

public static tout convertall<tin, tout, t, toutput>(this tin source     , converter<t, toutput> converter     , action<tout, toutput> adder)     tin : ienumerable<t>     tout : ienumerable<toutput>, new() {     tout output = new tout();     foreach (var item in source)         adder(output, converter(item));     return output; } 

note result of you've lost deferred execution though.