c# - How to change ComboBox SelectedValue programmatically with MVVM -

i have combobox items a, b, c, d, e.

how can change selectedvalue of combobox after user selection, if user select list items "a", selectedvalue "d" (as if selected d himself).

xaml:

<stackpanel orientation="horizontal">     <textbox text="{binding path=name, updatesourcetrigger=propertychanged, mode=twoway}" height="25" width="100" />     <combobox          isdropdownopen="{binding isdropdownopen, mode=twoway, updatesourcetrigger=propertychanged}"          itemssource="{binding offsetvalues}"         selectedvalue="{binding nodecategory, mode=twoway}"           height="25" width="100" ishittestvisible="false" background="aliceblue">         <combobox.resources>             <sys:double x:key="{x:static systemparameters.verticalscrollbarwidthkey}">0</sys:double>         </combobox.resources>      </combobox> </stackpanel> 

viewmodel:

class viewmodel : viewmodelbase {      private ilist<string> offsetvalues =  new list<string>() { "mv", "v" };     public ilist<string> offsetvalues     {                 {             return offsetvalues;         }         set         {             offsetvalues = value;         }     }       private bool isdropdownopen;      public bool isdropdownopen     {         { return isdropdownopen; }         set         {             isdropdownopen = value;             onpropertychanged();         }     }      private string _name;     public string name     {         { return _name; }         set         {              _name = value;             onpropertychanged( "name" );              if( _name != "" )             {                 isdropdownopen = true;                 onpropertychanged( "isdropdownopen" );             }          }     }      private string _nodecategory;     public string nodecategory     {                 {             return _nodecategory;         }         set         {             if( convert.todouble( _name ) > 1000 )             {                 _name = "1.0";                  onpropertychanged( "name" );                  _nodecategory = offsetvalues[1];                  onpropertychanged( "nodecategory" );              }             else             {                  _nodecategory = value;                 onpropertychanged( "nodecategory" );              }          }     }  }   public class viewmodelbase : inotifypropertychanged {      protected virtual void onpropertychanged( [callermembername]string propertyname = null )     {         propertychanged.invoke( this, new propertychangedeventargs( propertyname ) );     }      public event propertychangedeventhandler propertychanged;  } 

thanks

add xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"

than can invoke command when selecteditemchanged like

    <combobox x:name="nodecategoriescombobox">  <i:interaction.triggers>             <i:eventtrigger eventname="selectionchanged">                 <i:invokecommandaction command="{binding updatenodecategorycommand}" commandparameter="{binding elementname=nodecategoriescombobox, path=selectedvalue}"/>             </i:eventtrigger>          </i:interaction.triggers> </combobox> 

than add updatenodecategorycommand , update nodecategory property

private relaycommand<string> _updatenodecategorycommand ;  public relaycommand<string> updatenodecategorycommand {  { return _updatenodecategorycommand ?? (_updatenodecategorycommand = new relaycommand<string>( nodecategory => { nodecategory=nodecategory }));  }  }