C# ListView Relay Command Binding

Question

Can someone help me with the list view with grid. I want when you click on an element that a function is called and I get the current item. I already have the following XAML code:

<ListView Name="lstView" ItemsSource="{Binding Path=SimResults}" >
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="SelectionChanged">
            <i:InvokeCommandAction Command="{Binding SelectedItemCommand}" CommandParameter="{Binding SelectedItem, ElementName=lstView}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
    <ListView.ItemContainerStyle>
        <Style TargetType="ListViewItem">
            <Setter Property="HorizontalContentAlignment" Value="Center"/>
        </Style>
    </ListView.ItemContainerStyle>
    <ListView.View>
        <GridView>
            <GridView.Columns>
                <GridViewColumn Header="FileUniqueID" Width="Auto" DisplayMemberBinding="{Binding Path=FileUniqueID}" />
                <GridViewColumn Header="XML" Width="Auto" DisplayMemberBinding="{Binding Path=XML}" />
                <GridViewColumn Header="Request" Width="Auto" HeaderStringFormat="" DisplayMemberBinding="{Binding Path=RequestShort}" />
                <GridViewColumn Header="RequestDate" Width="Auto" DisplayMemberBinding="{Binding Path=RequestDate}" />
                <GridViewColumn Header="Response" Width="Auto" DisplayMemberBinding="{Binding Path=ResponseShort}" />
                <GridViewColumn Header="ResponseDate" Width="Auto" DisplayMemberBinding="{Binding Path=ResponseDate}" />
                <GridViewColumn Header="ResendCounter" Width="Auto" DisplayMemberBinding="{Binding Path=ResendCounter}" />
            </GridView.Columns>
        </GridView>
    </ListView.View>
</ListView>

In the cs file I have the following functions:

private Item selectedItem;
private RelayCommand selectedItemCommand;
this.selectedItemCommand = new RelayCommand(this.SelectedItems);

        public Item SelectedItem
        {
            get { return selectedItem; }
            set { selectedItem = value; OnPropertyChanged("SelectedTrends"); }
        }

        public RelayCommand SelectedItemCommand
        {
            get
            {
                return this.selectedItemCommand;
            }

        }

        private void SelectedItems(object obj)
        {
            this.requestXml = this.selectedItem.DisplayName;
        }

When I select an element the selectedItems and I can get the item.

Hi I tested the code above and it worked fine. But I have problem. I have different tabs, when I click a different tab with the left click it always runs the SelectionChanged event and I get a Null reference exception.

user3231208 · Accepted Answer · 2015-07-23 13:34:55Z

1

One solution is to create a property for the "SelectedItem" from the listView.

So, in your VM:

private YourType _selectedResult;
public YourType SelectedResult
{
    get { return _selectedResult; }
    set { _selectedResult= value; OnPropertyChanged("SelectedResult"); }
}

And bind this proprety on your ListView:

<ListView Name="lstView" ItemsSource="{Binding Path=SimResults}" SelectedItem="{Binding SelectedResult}">

answered Jul 23, 2015 at 13:34

user3231208

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6 Comments

user2644964 Over a year ago

Hi, thanks for your reply now the code above works but the SelectionChanged event also runs when I change to a different tab and I get a Null reference. Do you know how I can accomplish the the event is only accepted for a click on an item on the list view.

user3231208 Over a year ago

You don't need the SelectionChanged Event anymore. When you select another element in your ListView, the setter of SelectedResult is executed. (Maybe you have to specify the "Mode=TwoWay" in your binding in SelectedItem)

user2644964 Over a year ago

Hi thanks for you reply. If I debugged the code and select an item in the listview with left click the getter and setter isn't called I updated my current code in the main post.

user2644964 Over a year ago

Maybe can you also describe me how I can get things work with my first aproach, as now the SelectionChanged event runs when I change to a different tab and I get a Null reference. The event should be only accepted when you make a click on an item on the list view, so I can do it with Command and Relay Classes.

user3231208 Over a year ago

Did you try the event "ItemSelectionChanged" ?

|

user3869175 · Accepted Answer · 2015-07-23 09:28:57Z

1

Just make sure you initialize selectedItemCommand before InitializeComponent() in the ctor, eg:

public MainWindow()
{
    this.selectedItemCommand = new RelayCommand(this.SelectedItems);

    InitializeComponent();
}

answered Jul 23, 2015 at 9:28

user3869175

2 Comments

user2644964 Over a year ago

Hi, thanks for your reply now the code above works but the SelectionChanged event also runs when I change to a different tab and I get a Null reference. Do you know how I can accomplish the the event is only accepted for a click on an item on the list view.

user3869175 Over a year ago

@user2644964: what if you modify SelectedItems to return immediately in case a null is received in the parameter?

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