c# - Wpf binding problem -

i have in window rectangle tooltip, clicking button suppose change tooltip text doesn't.

xaml:

 <grid>     <grid.rowdefinitions>         <rowdefinition />         <rowdefinition />     </grid.rowdefinitions>      <grid.resources>         <tooltip x:key="@tooltip">             <textblock text="{binding name}" />         </tooltip>     </grid.resources>      <rectangle width="200" height="200" fill="lightblue" verticalalignment="center" horizontalalignment="center"             tooltip="{dynamicresource @tooltip}" />     <button click="button_click" grid.row="1" margin="20">click me</button> </grid> 

code behind:

public partial class window1 : window {      public window1()     {         datacontext = new person { name = "a" };         initializecomponent();     }      private void button_click(object sender, routedeventargs e)     {         datacontext = new person { name = "b" };     } } 

change binding to:

example:

<tooltip x:key="@tooltip">     <textblock text="{binding relativesource={relativesource mode=self}, path=parent.placementtarget.datacontext.name}" /> </tooltip> 

reason:

the reason works , yours doesn't because textblock element never gets notified of change in property named name bind in code.

to fix that, in example, textblock bound parent (tooltip) > placementtarget (button) > datacontext (person) > name property. here textblock has reference placementtarget in case button. button notifies textblock of change in it's datacontext property value on notification, textblock updates itself.