c# 4.0 - Type parameters - get concrete type from type T : IMyInterface -

-

suppose have list<imyinterface>...

i have 3 classes implement imyinterface: myclass1, myclass2, , myclass3

i have readonly dictionary:

private static readonly dictionary<type, type> declarationtypes = new dictionary<type, type> {     { typeof(myclass1), typeof(funnyclass1) },     { typeof(myclass2), typeof(funnyclass2) },     { typeof(myclass3), typeof(funnyclass3) }, };

i have interface, ifunnyinteface<t> t : imyinterface

i have method:

public static ifunnyinterface<t> converttofunnyclass<t>(this t node) t : imyinterface {     if (declarationtypes.containskey(node.gettype())) {         ifunnyinterface<t> otherclassinstance = (funnyinterface<t>) activator.createinstance(declarationtypes[node.gettype()], node);         return otherclassinstance;     }     return null; }

i'm trying call constructor of funnyclasses , insert parameter myclass object. don't want know object is: want instantiate funnyclass myclass parameter.

what happens when call converttofunnyclass, t of type imyinterface, , when try cast funnyinterface<t>, says can't convert funnyclass1, instance, funnyinterface<imyinterface>

my current workaround (not beautiful one), this:

public static dynamic converttofunnyclass<t>(this t node) t : imyinterface {     if (declarationtypes.containskey(node.gettype())) {         var otherclassinstance = (funnyinterface<t>) activator.createinstance(declarationtypes[node.gettype()], node);         return otherclassinstance;     }     return null; }

and don't because return type dynamic, when access somewhere else, have no idea type is, , lose intellisense, , stuff. don't know performance implications either.

any clues?

thanks in advance!

resolution

as i'm using c# 4.0, stop casting errors using covariance (output positions only), , changed ifunnyinterface to

ifunnyinteface<out t> t : imyinterface

thank replies.

essentially, problem trying convert funnyinterface<t> funnyinterface<imyinterface>. has been mentioned several times (one example here, more information here), not valid in circumstances. in .net 4, when generic type interface or delegate, , type parameter has been explicitly declared variant in or out, can perform conversion.

is funnyinterface interface?


Comments

Post a Comment

Popular posts from this blog

razor - Is this a bug in WebMatrix PageData? -

-
i think may have found bug in webmatrix's pagedata, not sure. concerns how pass data partial page calling page. in webmatrix documentation (tutorials, e.g. " 3 - creating consistent look ", , example code), pagedata recommended mechanism pass data between pages (e.g. content page layout page, or partial page). however have found not work other way, pass data partial page calling page. modifying or adding entries in pagedata in partial page, not seem calling page. cutting right down simplest possible example, in test page may have this: @{ pagedata["test"] = "initial entry"; } <p>before calling partial page, test value @pagedata["test"]</p> @renderpage("_testpartial.cshtml") <p>after returning calling page, test value @pagedata["test"]</p> and in _testpartial.cshtml page might have this: @{ pagedata["test"] = "modified entry"; } <p>in partial page...
Read more

c# - How to set Z index when using WPF DrawingContext? -

-
how set z-index drawing object when using drawingcontext.drawxxx() methods? the object drawn last have higher z index. can't change index of drawn objects. way draw in order. if using wpf (as placed tag), can use, example, canvas control. create shapes need like polyline obj = new polyline(); //... // ... set properties of obj and add them canvas uielementcollection: yourcanvasname.children.add(obj); //or yourcanvasname.children.insert(i, obj); first items of collection have higher z index. advantages in way: no need redraw on window changes, can anytime move objects , change order.
Read more

c# - Cloning WPF controls and object hierarchies -

-
i have problems cloning object hierarchie. it's toolkit modelling applications, toolbox contains class instances prototypes. i'm having hard time cloning these :) the following code shows problem: public abstract class shape { protected list<uielement> elements; private canvas canvas; ... public canvas getcanvas() { ... }; } public class movableshape : shape { protected ... propertya; private ... propertyxy; ... } public abstract class abstractlayout : movableshape, ... { ... } public class somelayoutclass : abstractlayout, ... { ... } public class acontainingclass { somelayoutclass layout { get; set; } ... } when insert object of acontainingclass project worksheet, should cloned. far tried manual cloning (which fails because of private fields in base classes) , binary serialization ( binaryformatter , memorystreams ). the first approach lacks way call base.clone() method (or wrong?), latter not work because uielement s aren't...
Read more