Get the values of a SelectedItem in wpf

问题

I have a ListBox in a WPF Page each Item of which consists of two Labels. I have assigned them the names FirstName, LastName:

<ListBox.ItemTemplate>
            <DataTemplate>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="Auto"/>
                        <ColumnDefinition Width="Auto"/>
                    </Grid.ColumnDefinitions>
                    <TextBlock Grid.Column="0" Name="FirstName" Text="{Binding FirstName}" Margin="0,0,10,0"/>
                <TextBlock Grid.Column="1" Name="LastName" Text="{Binding LastName}" HorizontalAlignment="Left"/>
                </Grid>
            </DataTemplate>
        </ListBox.ItemTemplate>

When the user selects an Item of the Listbox, I want to hold their values separately in order to pass them to another Page. I try to this end in the code behind the code:

 ListItemCollection lbi = List1.SelectedItem as ListItemCollection;

        string first = lbi.FirstListItem.DataContext.ToString();
        string last = lbi.LastListItem.DataContext.ToString();

However I get a nullReferenceException at the definition of strings? What is wrong in this way? How can I get the SelectedItem values?

Update: The Binding values derive from an SQLAdapter with a SQL Query. See the code behind:

SqlDataAdapter dAdapt1 = new SqlDataAdapter(sqlStr1, cnStr);

        DataSet dataSet1 = new DataSet();
        dAdapt1.Fill(dataSet1);

        List1.DataContext = dataSet1.Tables[0];

回答1:

DataTable and ListBox##

myDataSet.BookTable. firstColumn and lastColumn.

binding ready

adapter.Fill(myDataSet, "BookTable");

myListBox.DataContext = myDataSet;

binding begin

3.XAML

<ListBox ItemsSource="{Binding Path=BookTable}"

4. Window.Resources>

<DataTemplate x:Key="BookItemTemplate">
                <Grid>
  <TextBlock Text="{Binding Path=first}" Grid.Column="0"/> 
  <TextBlock Text="{Binding Path=last}" Grid.Column="1" />

ItemTemplate ="{StaticResource BookItemTemplate}"/>

binding end

DataRowView d1=List1.SelectedItem as DataRowView;
string first =d1["first"].tostring();
string last =d1["last"].tostring();

回答2:

As Andy has already commented, List1.SelectedItem is not a ListItemCollection, so you cannot cast to that type, hence lbi is null.

In the DataTemplate you're binding to properties FirstName and LastName. There must be a class that defines these properties, let's call it Person.

I guess the following, because you haven't shown it. You're binding the ItemSource of the ListBox to a collection of Person objects, provided by some property of the object that is returned by dataSet1.Tables[0] (because you set List1.DataContext to that value).

So what you would have to write to get the selected item is this:

Person lbi = List1.SelectedItems as Person;

and replace Person by whatever that type really is in your application.

来源：https://stackoverflow.com/questions/9239003/get-the-values-of-a-selecteditem-in-wpf

标签

wpf

listbox