设置组合框的selectedValue

Question

I have a ComboBox 'cbSkillLevel' to which I am binding data as shown bellow to populate the list. It works fine. I have a list box with items, based on the items selection I need to set different value to the 'cbSkillLevel'. How do I set the value of combobox to the value I want.

What I tried is bellow.

Your help much appreciated.

 <ComboBox Grid.Column="3" x:Name="cbSkillLevel" Margin="0,0,10,0" IsEnabled="{Binding ElementName=SkillsPage, Path=setIsEnabled, Mode=OneWay}">
     <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock FontSize="26" Foreground="Black" Text="{Binding Value}" />
        </DataTemplate>
     </ComboBox.ItemTemplate>
 </ComboBox>

List<Lookup> skillLevel = dbOperation.getLookupData("Skill_Level");
cbSkillLevel.ItemsSource = skillLevel;


private void lbSkills_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
   clearFields();
   clearTopicsForm();
   var skillobj = (lbSkills.SelectedItem as Skill);

   if (skillobj != null)  
   { 
       selected_SkillDescription = skillobj.SkillDescription;
       tbNotes.Text = skillobj.Notes;
       tbDescription.Text = selected_SkillDescription;
       /*I TRIED THE BELLOW OPTION BUT DID NOT WORK.*/
       //cbSkillLevel.SelectedItem = skillobj.SkillLevel;
       //cbSkillLevel.SelectedIndex = cbSkillLevel.Items.IndexOf(skillobj.SkillLevel.ToString());                
       //cbSkillLevel.SelectedIndex = 1;
       //cbSkillLevel.ItemsSource = tempListSkillLevel;
       cbSkillLevel.SelectedValue = skillobj.SkillLevel.ToString();
       cbSkillType.SelectedItem = skillobj.SkillType;
       tbWarningWeeks.Text = skillobj.WarningWeeks.ToString();
       dpValidFrom.Date = skillobj.ValidFrom;
       dpValidUntil.Date = skillobj.ValidUntil;
       /*load topics for this skill*/
       loadTopicsFromDB(skillobj.SkillDescription);
       //set the fields as read only
       setIsEnabled = false;
       addEditButton();            
     }
  }

I though using 'cbSkillLevel.SelectedValue = skillobj.SkillLevel.ToString();' should work, but it does not. My guess is cuz the binding is set to the value 'Value'

<TextBlock FontSize="26" Foreground="Black" Text="{Binding Value}" />

And while setting a value I am assigning from Skill object. How can I set value 'cbSkillLevel.SelectedValue = skillobj.SkillLevel.ToString();'

class Skill 
{
    [SQLite.PrimaryKey,   SQLite.AutoIncrement]
    public int Id { get; set; }
    public string SkillDescription { get; set; }
    public string SkillType { get; set; }
    public string SkillLevel { get; set; }
    public DateTime ValidFrom { get; set; }
    public DateTime ValidUntil { get; set; }
    public int WarningWeeks { get; set; }
    public string Notes { get; set; }
}

class Lookup
{
    [SQLite.PrimaryKey, SQLite.AutoIncrement]
    public int LookupId { get; set; }
    public string Type { get; set; }
    public string Value { get; set; }
}

Answer 1

SelectedItem probobly don't work since the objects are differnt physcials objects, created in seperate lists. That you used {Binding Value} isn't the problem, that is only the visual representation of your objects and have nothing to do with the selection. The thing you need to do is to tell the combobox WHAT value that is the "SelectedValue" on that object. that is done in the XAML and suggestly to Value since that seams to be unice to your objects(?)

<ComboBox SelectedValuePath="Value" ...

Then this should work:

cbSkillLevel.SelectedValue = skillobj.SkillLevel.Value;

Answer 2

ItemSource is a List of Lookup, so the only way to set the "selected" must also be of Lookup type.

cbSkillLevel.SelectedValue = skillobj.SkillLevel.ToString();

This will only work if you already have established an ItemSource with

IEnumerable<string>

ComoboBox is an ItemsControl. You can see a detailed info here https://msdn.microsoft.com/en-us/library/system.windows.controls.itemscontrol(v=vs.110).aspx

Answer 3

Add DisplayMemberPath and SelectedValuePath to your xaml bindings that is DisplayMemberPath is what property of object should be shown to the user and SelectedValuePath is what property it selects internally so its like this for example if i want to bind my fruits collection to combobox, i would like display fruit name but select its id so my properties will be

 DisplayMemberPath = "FruitName"
 SelectedValuePath = "FruitId"

And later in your selectionchanged event, you can set its value with cbSkillLevel.SelectedValue. In our example, it will be the fruit id as we bound it as SelectedValuePath.