c# - Replace casting with better pattern -

i'm working on simple client-server solution client can send different types of commands server , specific results. commands can have different properties. i'd have architecture specific command handler chosen based on type of command handles. created basic infrastructure follows:

public interface icommand { }  public class commanda: icommand {     public string customproperty { get; set; } }  public class commandb: icommand { } 

each command has own commandhandler responsible handling command , returning result. inherit commandhandlerbaseclass:

public interface icommandhandler {     bool canhandle(icommand command);     ireply handle(icommand command); }  public abstract class commandhandlerbase<tcommand> : icommandhandler     tcommand : class, icommand {     public bool canhandle(icommand command)     {         return command tcommand;     }      public ireply handle(icommand command)     {         return handle(command tcommand);     }      public abstract ireply handle(tcommand command); }  // specific handler public class commandahandler : commandhandlerbase<commanda> {     public override ireply handle(commanda command)     {         //handling command , returning result         return null;     } } 

i created class responsible choosing suitable handler , returning result:

public interface ireplycreator {     ireply getreply(icommand command); }  public class replycreator : ireplycreator {     private readonly ienumerable<icommandhandler> _commandhandlers;      public replycreator(ienumerable<icommandhandler> commandhandlers)     {         _commandhandlers = commandhandlers;     }      public ireply getreply(icommand command)     {         var commandhandler = _commandhandlers             .firstordefault(x => x.canhandle(command));          if (commandhandler == null)             return null;         return commandhandler.handle(command);     } } 

i don't casting in commandhandlerbase class, can't find patterns avoid it. create generic interface shown below, how register , choose specific handler in replycreator then?

public interface icommandhandler<tcommand>     tcommand : icommand {     bool canhandle(tcommand command);     ireply handle(tcommand command); } 

the commands received in server serialized json.net follows:

jsonconvert.serializeobject(new commanda(), new jsonserializersettings     {         typenamehandling = typenamehandling.all     };) 

so receive string need deserialized concrete command , handled suitable handler. there way of avoiding casts @ in such scenario? use structuremap ioc library.

why trying avoid cast? workarounds come mind now, not nicer this.

i avoid using as keyword purpose. fail silently in unlikely case when wrong type passed handler. in cases this, want exception thrown immediately, not somewhere later in code.