C# WPF InotifyPropertyChange Confusion -

i converting vbnet winforms project c# wpf. new both trying figure out.

i have project 2 wpf windows , viewmodel referenced project.

    public class sheepviewmodel : inotifypropertychanged {      private string _currenteventname; public string currenteventname {     { return _currenteventname; }         set             {               _currenteventname = value;               onpropertychanged("currenteventname");             }     }      static sheepviewmodel _details;     public static sheepviewmodel getdetails()     {         if (_details == null)             _details = new sheepviewmodel();         return _details;     }      public event propertychangedeventhandler propertychanged;      private void onpropertychanged(string prop)     {         if (propertychanged != null)             propertychanged(this, new propertychangedeventargs(prop));             console.writeline(prop + " has changed");     }    } 

the window display things looks this.

<window     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"     xmlns:vm="clr-namespace:sheepviewmodel;assembly=sheepviewmodel"     xmlns:shadereffectlibrary="clr-namespace:shadereffectlibrary;assembly=shadereffectlibrary" x:class="sheep_score_3._1.scorescreen"     mc:ignorable="d"     title="scorescreen" height="540" width="920" windowstartuplocation="centerscreen"> <window.datacontext>     <vm:sheepviewmodel/> </window.datacontext>  <viewbox x:name="stand1viewbox" rendertransformorigin="0.5,0.5"> <canvas x:name="standviewbox" height="112.513" margin="0,1100,2,0" verticalalignment="bottom" rendertransformorigin="0.493,0.473" background="#ff999999" width="2268">     <textblock x:name="currenteventname" canvas.left="270.9" textwrapping="wrap" width="1104.815" fontfamily="calibri" fontsize="29.333" fontstyle="italic" canvas.top="-1.649" text="{binding path=currenteventname}"/>     </canvas> </viewbox> 

my mainwindow control window looks this

<window x:class="sheep_score_3._1.mainwindow"     xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"     xmlns:vm="clr-namespace:sheepviewmodel;assembly=sheepviewmodel"     mc:ignorable="d"     title="mainwindow" height="433.689" width="941.194"> <window.datacontext>     <vm:sheepviewmodel/> </window.datacontext>     <grid margin="0,0,0,0">         <textbox x:name="currenteventname" height="23" margin="131.01,163.013,0,0" textwrapping="wrap" verticalalignment="top" horizontalalignment="left" width="327.151" text="{binding currenteventname, mode=twoway}"/> </grid> 

now, if type control window textbox appears on display window in textblock, bindings working , can see notifyproperychange fire. that's working great.

however, if change property programmatically, can still see notifypropertychange fire, textbox , textblock not update new value.

sheepviewmodel.sheepviewmodel.getdetails().currenteventname = "this new value"; 

am missing here? guidance on welcome, i've checked calling right property name , googled couple of days try , figure out, i'm stuck.

i'm surprised text updates work you; doesn't on side. here's why:

you have following snippet in both windows:

<window.datacontext>     <vm:sheepviewmodel/> </window.datacontext> 

this says: create new instance of sheepviewmodel , set window's datacontext. since have in both windows, each window have separate instance of viewmodel. currenteventname property instance property, value won't shared between instances , won't update properly.

when try programmatically update value, call sheepviewmodel.getdetails(). creates yet instance, totally unrelated ones used controls. therefore, don't see updates.

what want of above use 1 single viewmodel instance. this, can set datacontext of windows code behind. instead of using above xaml snippet, can use following constructor in windows:

public displaywindow() {     initializecomponent();     this.datacontext = sheepviewmodel.getdetails(); } 

this ensures windows refer singleton instance retrieved through getdetails method.