c# - Binding an element in a child View to a property of the parent ViewModel -

like title says, bind element in child view property of parent viewmodel.

is there caliburn.micro or default wpf xaml syntax this? mean, exact situation: bind parent viewmodel's property.

or should try achieve other way? so, best/easiest way it?

here basic caliburn.micro app example:

mainwindowviewmodel.cs

namespace bindingtoparentvmproperty.mvvm {     public class mainwindowviewmodel     {         public childviewmodel child { get; set; }         public string parentname { get; set; }          public mainwindowviewmodel()         {             child = new childviewmodel();             parentname = "peter griffin";         }     } } 

mainwindowview.xaml:

<usercontrol x:class="bindingtoparentvmproperty.mvvm.mainwindowview"              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"              mc:ignorable="d">     <grid width="200" height="200">         <contentcontrol name="child" />     </grid> </usercontrol> 

childviewmodel.cs:

using caliburn.micro;  namespace bindingtoparentvmproperty.mvvm {     public class childviewmodel     {         public bindablecollection<grandchildviewmodel> grandkids { get; set; }         public string childname { get; set; }          public childviewmodel()         {             childname = "stewie griffin";             grandkids = new bindablecollection<grandchildviewmodel>                 {                     new grandchildviewmodel {grandchildname = "stewie griffin jr."},                     new grandchildviewmodel {grandchildname = "rupert griffin jr."}                 };         }     } } 

childview.xaml:

<usercontrol x:class="bindingtoparentvmproperty.mvvm.childview"              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">     <stackpanel>         <!-- need bind mainwindowviewmodel.parentname-->         <textblock text="{binding path=howtobindto_parentname}"/>         <listview name="grandkids" />     </stackpanel> </usercontrol> 

grandchildviewmodel.cs:

namespace bindingtoparentvmproperty.mvvm {     public class grandchildviewmodel     {         public string grandchildname { get; set; }     } } 

grandchildview.xaml:

<usercontrol              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"              x:class="bindingtoparentvmproperty.mvvm.grandchildview"              mc:ignorable="d"               d:designheight="300" d:designwidth="300">     <stackpanel>         <textblock x:name="grandchildname" />         <!-- need bind childviewmodel.childname -->         <textblock text="{binding path=howtobindto_childname}"/>     </stackpanel> </usercontrol> 

it seems straightforward suggestion keep record of parent on child viewmodel (e.g. parent property). since want have viewmodels tied respective views, think become conceptually quite tricky if start bind properties , include information beyond scope of bound viewmodel.

also, whilst may not of concern particular project you're working on, if start including properties other usercontrols, you're implicitly creating links , dependencies, may come inconvenience if wish re-use controls elsewhere in non-hierarchical context.

that said, traverse ui tree required datacontext (viewmodel) parent control, , bind desired property using existing wpf syntax, kollegos suggests, using relativesource , ancestortype property.

in case, might this:

<usercontrol x:class="bindingtoparentvmproperty.mvvm.childview"          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"          xmlns:local="clr-namespace:yourprojectnamespacecontainingparentview"          mc:ignorable="d"           d:designheight="300" d:designwidth="300"> <stackpanel>     <!-- set our datacontext bind parent mainwindowviews datacontext (viewmodel) -->     <textblock text="{binding path=parentname}"         datacontext="{binding relativesource={relativesource                       findancestor, ancestortype={x:type local:mainwindowview}},                       path=datacontext}"/>     <listview name="grandkids" /> </stackpanel> 

relativesource documentation