VB.NET列表框选定的索引

Question

I seem to be having issues with the selected index on a list box.

The list box is having various items inserted depending on the user selection. An example would be:

LiIndex = ListBox1.Items.Count      
ListBox1.Items.Insert(LiIndex, "Item1")

LiIndex = ListBox1.Items.Count      
ListBox1.Items.Insert(LiIndex, "AND")

LiIndex = ListBox1.Items.Count      
ListBox1.Items.Insert(LiIndex, "Item2")

LiIndex = ListBox1.Items.Count      
ListBox1.Items.Insert(LiIndex, "AND")

LiIndex = ListBox1.Items.Count      
ListBox1.Items.Insert(LiIndex, "Item3")

This all work and displays without a problem. The issue I have is if I select the second of the two AND's. If I click the second "AND" in the list and then a button to fire a method, the selected index is always the index of the first "AND".

Dim listIndex as integer = ListBox1.SelectedIndex

I can't work out why, the listbox itself will always show the second one as selected, but the action will happen against the first one.

Any ideas as to where I am going wrong would be greatly appreciated.

Answer 1

It looks ok, but i think the index you are creating is wrong, or maybe you are reseting or deselecting the listbox when clicking the button or something...

I did this and it worked, i get index = 3 when selecting the second "AND" (and with a cleaner syntax)

ListBox1.Items.Insert(ListBox1.Items.Count, "Item1")
ListBox1.Items.Insert(ListBox1.Items.Count, "AND")
ListBox1.Items.Insert(ListBox1.Items.Count, "Item2")
ListBox1.Items.Insert(ListBox1.Items.Count, "AND")
ListBox1.Items.Insert(ListBox1.Items.Count, "Item3")

Answer 2

Wathever you want to achieve, handling the ListBox items directly is not a good place to start. You should use an ObservableList(Of String) as a property of your code and bind the list in xaml.
After that your code becomes : MyItemList.Add("My Item")
The issue might come from using SelectedItem in your code OR from the fact your're displaying same object twice (i once had a strange behaviour in a CheckBox displaying twice same object) you can get rid of that by defining/using a class to store the data : anyway, it is not just about a string, no ? so you can have an ItemInfo class with a ToString Overload for it to display OR you define a DataTemplate in your Window resource that has ItemInfo as DataType.

<DataTemplate DataType="{x:Type l:ItemInfo}">
        <TextBlock Text="{Binding ItemText}" />
</DataTemplate>  

and in your code you use, MyItemList beeing now an ObervableList(Of ItemInfo) : MyList.Add(New ItemInfo(" some text", ...) )
so you never have twice same item.

More work, but here we have more solid start to add data/functions after.