c# - WPF usercontrol Twoway binding Dependency Property -

i created dependency property in usercontrol, changes in usercontrol not notified viewmodel

usercontrol

<usercontrol x:class="dpsample.usercontrol1"          xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"          xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"          xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"           xmlns:d="http://schemas.microsoft.com/expression/blend/2008"           mc:ignorable="d"           d:designheight="300" d:designwidth="300"> <grid>     <textbox x:name="txtname"></textbox> </grid> 

usercontrol.cs

/// <summary> /// interaction logic usercontrol1.xaml /// </summary> public partial class usercontrol1 : usercontrol {     public usercontrol1()     {         initializecomponent();     }      #region sampleproperty       public static readonly dependencyproperty samplepropertyproperty                                             = dependencyproperty.register("sampleproperty",                                              typeof(string),                                              typeof(usercontrol1),                                              new propertymetadata(onsamplepropertychanged));       public string sampleproperty     {         { return (string)getvalue(samplepropertyproperty); }         set { setvalue(samplepropertyproperty, value); }     }       static void onsamplepropertychanged(dependencyobject obj, dependencypropertychangedeventargs e)     {         (obj usercontrol1).onsamplepropertychanged(e);     }     private void onsamplepropertychanged(dependencypropertychangedeventargs e)     {         string samplepropertynewvalue = (string)e.newvalue;          txtname.text = samplepropertynewvalue;     }      #endregion } 

mainwindow

<window     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:local="clr-namespace:dpsample" x:class="dpsample.mainwindow"     title="mainwindow" height="350" width="525"> <grid>      <local:usercontrol1 sampleproperty="{binding sampletext,mode=twoway}" horizontalalignment="left" margin="76,89,0,0" verticalalignment="top" width="99"/>     <button content="show" horizontalalignment="left" margin="76,125,0,0" verticalalignment="top" width="75" click="button_click"/>  </grid> 

mainwindow.cs

 public mainwindow()     {         initializecomponent();         this.datacontext = new mainviewmodel();     }      private void button_click(object sender, routedeventargs e)     {         var item = this.datacontext mainviewmodel;         messagebox.show(item.sampletext.tostring());     } 

mainviewmodel.cs

public class mainviewmodel : notifyviewmodelbase {     public mainviewmodel()     {         this.sampletext = "test";                }      private string _sampletext;     public string sampletext     {         { return _sampletext; }         set { _sampletext = value; onpropertychanged("sampletext"); }     } } 

bind textbox.text property in usercontrol sampleproperty this:

<textbox text="{binding sampleproperty,                         relativesource={relativesource ancestortype=usercontrol}}"/> 

now remove onsamplepropertychanged callback.

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you might register sampleproperty bind two-way default this:

public static readonly dependencyproperty     samplepropertyproperty = dependencyproperty.register(         "sampleproperty", typeof(string), typeof(usercontrol1),         new frameworkpropertymetadata(             null, frameworkpropertymetadataoptions.bindstwowaybydefault));