The Property 'Command' was not found in type 'InvokeCommandAction' for combobox

The Property 'Command' was not found in type 'InvokeCommandAction' for combobox

I have a combobox in silverlight mvvm. i need to wrote the event for combobox name 'SelectionChanged'. i Create the coding below but it gives an error.. "The Property 'Command' was not found in type 'InvokeCommandAction' "

Note: I am not using Silverlight Light. I'm using Silverlight5 and its a silverlight application.

<ComboBox x:Name="myComboBox" Width="150" ItemsSource="{Binding Items}" >                                     <ComboBox.ItemTemplate>                                         <DataTemplate>                                             <StackPanel>                                                 <TextBlock Text="{Binding Name}"/>                                             </StackPanel>                                         </DataTemplate>                                     </ComboBox.ItemTemplate>                                     <i:Interaction.Triggers>                                         <i:EventTrigger EventName="SelectionChanged">                                             <i:InvokeCommandAction Command="{Binding LoadCommand}" CommandParameter="{Binding SelectedItem, ElementName=myComboBox}" />                                         </i:EventTrigger>                                     </i:Interaction.Triggers>                                 </ComboBox> 

this line the error comes.

<i:InvokeCommandAction Command="{Binding LoadCommand}" CommandParameter="{Binding SelectedItem, ElementName=myComboBox}" /> 

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