How to Determine Whether an Item from a List has been Selected Programmatically

Question

I actually have two ListBoxes, and the user has the option of selecting an item from either ListBox. I'd like to have a way to determine whether an item has already been chosen from either list if a user tries to select it again. I do not want to indicate this by marking some sort of visual on the device's screen, because the item from either ListBox is already highlighted when selected. I just want to perform a check when the user selects an item from either ListBox to determine if an item has been selected, and if so display a message and not allow that item to be reselected.

XAML

<ListBox x:Name="ListBoxEffects" SelectionMode="Single" ItemsSource="{Binding}" Margin="{Binding}"
                     toolkit:TiltEffect.IsTiltEnabled="True" SelectionChanged="ListBox_SelectionChanged" />

        <ListBox x:Name="ListBoxEffects1" SelectionMode="Single" ItemsSource="{Binding}" Margin="{Binding}"
                     toolkit:TiltEffect.IsTiltEnabled="True" SelectionChanged="ListBox_SelectionChanged" />

How do I keep track of what has been selected and what hasn't? To note, ListBoxEffects has 20 items and ListBoxEffects1 has 10 items, so there are 30 items total.

Answer 1

Since the items in the list are less, you can put the selected items in a collection and can validate through this collection while adding new items to it. If the item already exists you can display a message.

Answer 2

you can bind the SelectedItem, then you 'll get which item is selected in the code and you can show further messages like it is already been selected.

<ListBox x:Name="ListBoxEffects" SelectedItem="{Binding Model.SelectedList1Item,Mode=TwoWay}" SelectionMode="Single" ItemsSource="{Binding}" Margin="{Binding}"
                 toolkit:TiltEffect.IsTiltEnabled="True" SelectionChanged="ListBox_SelectionChanged" />

    <ListBox x:Name="ListBoxEffects1" SelectedItem="{Binding Model.SelectedList2Item,Mode=TwoWay}" SelectionMode="Single" ItemsSource="{Binding}" Margin="{Binding}"
                 toolkit:TiltEffect.IsTiltEnabled="True" SelectionChanged="ListBox_SelectionChanged" />

Answer 3

在您的代码中，您已经有SelectionChanged事件。您将使用SelectedValue属性获取selectedvalue。然后在SelectionChanged事件内部，您可以检查selectedvalue并使用它来做任何您想做的事情。

Answer 4

My requirement was slightly different but this logic kinda worked for me.

in xaml make stackpanel inside both the the listbox datatemplate

    <datatemplate>
    <stackpanel tap="stk_Tap">
<!--list item template, whatever it is-->
    </Stackpanel>
    </Datatemplate>

now in cs

just make two global int variables

int previousselectedindexList1=-1;

int previousselectedindexList2=-1;

now for tap event

 stk_Tap
    {
      if (previousselectedindexList1!= lbLocationHistory.SelectedIndex)
      {
        previousselectedindexList1= lbLocationHistory.SelectedIndex;
      }
      else
      {
        //your message here
        previousselectedindexList1= -1;
       }
    }

make same tap event for the stackpanel of other listbox

Hope something like this helps.

Answer 5

    private void ListBox_SelectionChanged( object sender, SelectionChangedEventArgs e)
    {
        String lstbox = (sender as TextBox).Name;
        switch(lstbox)
        {

            case "ListBoxEffects":
                    if(ListBoxEffects.SelectedItem == ListBoxEffects1.SelectedItem)
                    {
                        MessageBox.Show("Item already selected");
                    }
                    else
                     //ur code
                break;

           case "ListBoxEffects1":
                if(ListBoxEffects.SelectedItem == ListBoxEffects1.SelectedItem)
                {
                    MessageBox.Show("Item already selected");
                }
                else
                     //ur code
                break;
        }

    }