WPF

<ComboBox ItemsSource="{Binding Path=DataContext.ProjectTypes, 
                RelativeSource={RelativeSource FindAncestor, AncestorType={ x:Type views:ClientListView}}}"
            SelectedItem="{Binding Path=DataContext.SelectedProjectType, 
                RelativeSource={RelativeSource FindAncestor, AncestorType={ x:Type views:ClientListView}}, Mode=TwoWay}"/>

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

<ListView>
			<i:Interaction.Triggers>
				<i:EventTrigger EventName="ItemContextMenuOpening">
					<local:EventToCommand Command="{Binding ItemContextMenuOpeningCommand}" PassEventArgsToCommand="True" />
				</i:EventTrigger>
			</i:Interaction.Triggers>

</ListView>

<Window x:Class="Events.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:entities="clr-namespace:Events"
        xmlns:g="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WPF4"
        xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
        Title="MainWindow" Height="350" Width="525">
    
    <Window.Resources>
        <DataTemplate DataType="{x:Type entities:Customer}">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding CustomerName}"/>
            </StackPanel>
        </DataTemplate>
    </Window.Resources>
    
    <Grid>

        <ListBox ItemsSource="{Binding Customers}">
            
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="ListBoxItem.MouseDoubleClick">
                    <g:EventToCommand Command="{Binding DoubleClickCommand}" PassEventArgsToCommand="True" />
                </i:EventTrigger>
            </i:Interaction.Triggers>

        </ListBox>

    </Grid>
    
</Window>

using System.Collections.ObjectModel;
using System.Windows.Input;
using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;

namespace Events
{
    public class MainWindowViewModel : ViewModelBase
    {
        private ObservableCollection<Customer> _Customers = new ObservableCollection<Customer>();
        public ObservableCollection<Customer> Customers
        {
            get { return _Customers; }
            set
            {
                if (_Customers != value)
                {
                    _Customers = value;
                    RaisePropertyChanged("Customers");
                }
            }
        }

        private ICommand _DoubleClickCommand;
        public ICommand DoubleClickCommand
        {
            get
            {
                if (_DoubleClickCommand == null)
                {
                    _DoubleClickCommand = new RelayCommand(doubleClicked);
                }
                return _DoubleClickCommand;
            }
        }

        public MainWindowViewModel()
        {
            Customers.Add(new Customer { Id = 0, CustomerName = "Jack Smith"});
            Customers.Add(new Customer { Id = 1, CustomerName = "Pete Jones" });
            Customers.Add(new Customer { Id = 2, CustomerName = "William Jackson" });
        }

        private void doubleClicked()
        { 
            // Handle the double click
        }
    }
}

Kevin Marois wrote:

<i:EventTrigger EventName="ListBoxItem.MouseDoubleClick">

<ListBox x:Name="myListBox"
            ItemsSource="{Binding Customers}">
            
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="MouseDoubleClick">
                    
            <g:EventToCommand Command="{Binding DoubleClickCommand}"
                                CommandParameter="{Binding SelectedItem, ElementName=myListBox, Mode=OneWay}" 
                                PassEventArgsToCommand="True" />
                    
        </i:EventTrigger>
    </i:Interaction.Triggers>

</ListBox>