c# - How to update binding to DataContext from within view model? -

this question has answer here:

• wpf binding without path converter, update 3 answers

i have binding:

<textblock text="{binding converter={local:converter}}" /> 

with converter:

public object convert(object value, type targettype, object parameter, cultureinfo culture) {     var vm = (viewmodel)value;     return vm.someproperty; } 

changing someproperty doesn't update value on screen. converter not called.

how update such binding within view model?

note: in real project converter used perform calculation , returning result. in fact multibinding similar bindings different view models. had problem , able narrow down case simple binding, binding not used bind property, this.

---

mcve xaml:

<stackpanel>     <textblock text="{binding converter={local:converter}}" />     <button content="..." click="button_click" /> </stackpanel> 

and code:

public partial class mainwindow : window {     viewmodel _vm = new viewmodel();      public mainwindow()     {         initializecomponent();         datacontext = _vm;     }      void button_click(object sender, routedeventargs e) => _vm.someproperty += "b"; }  public class viewmodel : inotifypropertychanged {     public event propertychangedeventhandler propertychanged;     public void onpropertychanged(string property) => propertychanged?.invoke(this, new propertychangedeventargs(property));      string _someproperty = "a";     public string someproperty     {         { return _someproperty; }         set         {             _someproperty = value;             onpropertychanged(nameof(someproperty));         }     } }  public class converter : markupextension, ivalueconverter {     public override object providevalue(iserviceprovider serviceprovider) => this;      public object convert(object value, type targettype, object parameter, cultureinfo culture)     {         var vm = (viewmodel)value;         return vm.someproperty;     }      public object convertback(object value, type targettype, object parameter, cultureinfo culture)     {         throw new notimplementedexception();     } } 

if viewmodel set datacontext of view. can bind property using <textblock text="{binding someproperty}" />

from comments, if bind whole viewmodel, because converter more stuff, convert type, or thing. have @ this: answer