c# - WPF, covariance, contravariance, and binding in .Net -

i need make settings manager can't use appsettings or applicationsettings because need specific behaviour (adding/removing settings @ runtime, loading from/saving in multiple files...).

the problem i'm encountering finding solution end result want. here exemple of should in use case :

public partial class mywindow : window {     private settingsmanager _settingsmanager;      public myclass()     {         _settingsmanager.add(new option(){name = "option1", displayname = "option 1", defaultvalue = "sometext", value = "sometext"});         _settingsmanager.add(new option(){name = "option2", displayname = "option 2", defaultvalue = 5});         _settingsmanager.add(new option(){name = "option3", displayname = "option 3"});         _settingsmanager["option2"] = 10;         _settingsmanager["option3"].defaultvalue = brushes.black;         _settingsmanager["option3"] = brushes.white;          datacontext = _settingsmanager;     } } 

with it's corresponding xaml file :

<window x:class="anotherproject.mywindow"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     title="mainwindow" height="350" width="525" loaded="window_loaded"> <grid>     <itemscontrol itemssource="{binding}">         <itemscontrol.resources>             <datatemplate datatype="{x:type string}">                 <label content="{binding}"/>             </datatemplate>             <datatemplate datatype="{x:type int}">                 <label content="{binding}" foreground="red"/>             </datatemplate>             <datatemplate datatype="{x:type brush}">                 <label content="{binding tostring}" foreground="{binding}"/>              </datatemplate>         </itemscontrol.resources>     </itemscontrol> </grid> 

i aware wpf not support int , string types , produces errors, used demonstrative example, real types not produce errors.

i tried inheriting settingsproperty, used appsettings, seemed complex i'm trying , couldn't assign values without casting.

i tried using generics there problem in type recognition. following line did not work unless object cast appropriate type :

_settingsmanager["option2"] = 10; 

i know ways achieve of use case parts separately, not 1 of above mentioned.

is possible achieve that?

update : here settingmanager looks like

    public class settingsmanager : observablecollection<option> {     public settingsmanager()     {     }      public settingsmanager(ienumerable<option> options)     {         if (options != null)         {             foreach(var option in options)             {                 this.add(option);             }         }     }      public option this[string key]     {                 {             return this.where(x => x.name == key).firstordefault();         }         set         {             var res = this.first(x => x.name == key);             if (res != null)             {                 this.setitem(this.indexof(res), value);             }             else                 this.add(value);         }     }      public settingsmanager addrange(ienumerable<option> options)     {         if (options != null)         {             foreach(var option in options)             {                 this.add(option);             }         }         return this;     }      public void resetall()     {         this.tolist().foreach(x => x.reset());     } } 

the itemscontrol has itemssource set collection of option, meaning each data item of type option. datatemplate datatype cannot filter on different types of value (a property of option) apply different templates. in case should use datatemplateselector, define datatemplates resources in xaml convenience (we can find them in code behind inside selecttemplate method):

public class optiontemplateselector : datatemplateselector {    public override datatemplate selecttemplate(object item, dependencyobject container){       var option = item option;       if(option != null){           var itemcontainer = container frameworkelement;           if(option.value int){              return itemcontainer.findresource("intoption") datatemplate;           }           else if(option.value string){              return itemcontainer.findresource("stringoption") datatemplate;           }           else if(option.value brush){              return itemcontainer.findresource("brushoption") datatemplate;           }       }       return null;    } } 

define template selector resource in xaml:

<local:optiontemplateselector x:key="ot"> 

the remaining xaml:

<itemscontrol itemssource="{binding}"               itemtemplateselector="{staticresource ot}">              <itemscontrol.resources>           <datatemplate x:key="stringoption">             <label content="{binding value}"/>         </datatemplate>         <datatemplate x:key="intoption">             <label content="{binding value}" foreground="red"/>         </datatemplate>         <datatemplate x:key="brushoption">             <label content="{binding value}" foreground="{binding}"/>          </datatemplate>     </itemscontrol.resources> </itemscontrol>