Command Binding WPF VB.NET -

help me resolve command binding issue i'm having toggleheightmeasurementon property (see code below). reasons, content binding working, command not binding.

view code

<usercontrol x:class="heightmeasurementselector"              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:common="clr-namespace:harvestercore;assembly=harvestercore"              mc:ignorable="d"               d:designheight="85" d:designwidth="550" fontsize="16">   <grid >     <grid.columndefinitions>       <columndefinition width="40*"/>       <columndefinition width="100*"/>       <columndefinition width="40*"/>       <columndefinition width="100*"/>       <columndefinition width="50*"/>       <columndefinition width="120*"/>       <columndefinition width="30*"/>     </grid.columndefinitions>      <grid.rowdefinitions>       <rowdefinition/>        </grid.rowdefinitions>      <button content="{binding heightmeasurementon,mode=oneway}" command="{binding toggleheightmeasurementon, mode=oneway}" style="{dynamicresource metrobutton}"         background="{binding heightmeasurementon,mode=oneway,converter={staticresource backgroundcvtr}}" fontweight="bold" grid.column="0" margin="2"/>     <label content="earheight" horizontalalignment="center" verticalalignment="center" grid.column="1" style="{dynamicresource boldlabel}"/>     <label content="{binding heightmeasurementprismname, mode=oneway}" style="{dynamicresource boldlabel}" verticalalignment="center"           visibility="{binding heightmeasurementon, mode=oneway}" horizontalalignment="center" grid.column="3"/>     <label   content="{binding heightmeasurementonuom, mode=oneway}" style="{dynamicresource boldlabel}"  verticalalignment="center"          visibility="{binding heightmeasurementon, mode=oneway, converter={staticresource converter}}" horizontalalignment="center" grid.column="5"/>     </grid> </usercontrol> 

code behind

public class heightmeasurementselector     public sub new(vm heightmeasurementviewmodel)        initializecomponent()         me.datacontext = vm     end sub  end class 

viewmodel code

public class heightmeasurementviewmodel     inherits viewmodelbase      private model heightmeasurementmodel      public sub new(model heightmeasurementmodel)         me.model = model      end sub      public readonly property heightmeasurementon boolean                     return model.heightmeasurementon         end     end property      public readonly property toggleheightmeasurementon icommand                     return new delegatecommand(sub()                                            model.heightmeasurementon = not model.heightmeasurementon                                    end sub)         end     end property  end class 

model code

private earhton boolean  public property heightmeasurementon boolean                                     return earhton         end         set(value boolean)             earhton = value             if earhton                 taker.visualtrait_on()             elseif (not heightmeasurementon ) andalso (not plantheighton) andalso (not vtmodel.visualtraitactive)             taker.visualtrait_off()             end if              raiseevent earheightonchanged(heightmeasurementon)             raiseevent dialogonchanged(dialogon)         end set     end property