I am using Compact Framework 3.5 and have the following code:
var timeouts = new[] {1, 2, 3, 4, 5};
ddlTimeout.DataSource = timeouts;
ddlTimeout.SelectedValue = 3;
And receive the following error on setting selected value. Where's an issue?
Cannot set the SelectedValue in a ListControl with an empty ValueMember
Note: It works well if I use List<> of class objects as DataSource with specifying DisplayMember and ValueMember for the ComboBox.
The error is
"Cannot set the SelectedValue in a ListControl with an empty
ValueMember."
Try this instead:
var timeouts = new[] {1, 2, 3, 4, 5};
ddlTimeout.DataSource = timeouts;
ddlTimeout.SelectedItem = 3;
You have to have the ValueMember set for SelectedValue to work. The documentation shows the difference:
ComboBox.SelectedValue Gets or sets the value of the member property specified by the ValueMember property
ComboBox.SelectedItem Gets or sets currently selected item in the ComboBox.
Related
Here's code to populate a combobox with Linq-to-SQL:
private void FillEmbCB()
{
DataClasses1DataContext dc = new DataClasses1DataContext();
var emb = from e in dc.EMBALLAGES
select new
{
e.EMB_CODE,
e.EMB_LIB
};
Emb1CB.ItemsSource = emb;
Emb1CB.SelectedValuePath = "EMB_CODE";
Emb1CB.DisplayMemberPath = "EMB_LIB";
Emb1CB.SelectedItem = "HOUSSE PROTEC PALETTE"; // Nothing appears in the combobox
dc.Dispose();
}
At the end of that code, I want to choose an item from the combobox I've just populated, and show it in the combobox, but nothing appears, the combobox is always empty.
Here's my Xaml markup:
<ComboBox x:Name="Emb1CB" Width="200" FontSize="12"
SelectionChanged="Emb1CB_SelectionChanged"/>
SelectedValuePath is used for data binding (which you should be doing instead of manipulating the GUI directly like this, but that's another discussion). If you want to set SelectedItem yourself then you need to set the value to the parent object that contains the value, e.g.:
using System.Linq;
Emb1CB.SelectedItem = emb.FirstOrDefault(x => x.EMB_CODE == "HOUSSE PROTEC PALETTE");
Let's say I have a ComboBox named comboBox.
I want to disable ComboBox's auto complete feature.
At first I thought that everything I need to do is setting its IsTextSearchEnabled to false as following
comboBox.IsTextSearchEnabled = false;
But it seems doing this cause some unexpected side effects.
When IsTextSearchEnabled = true (which is default with combobox) if you try to set a value for ComboBox's Text, the combobox will find corresponding index in its ItemsSource and update the its SelectedIndex accordingly.
List<string> lst = new List<string>();
lst.Add("1");
lst.Add("2");
lst.Add("3");
lst.Add("4");
lst.Add("5");
MessageBox.Show(comboBox.SelectedIndex.ToString()); // -1
comboBox.ItemsSource = lst;
comboBox.Text = "3";
MessageBox.Show(comboBox.SelectedIndex.ToString()); // 2
Now when I tried to set IsTextSearchEnabled = false, the ComboBox's SelectedIndex doesn't get updated when its Text changes.
List<string> lst = new List<string>();
lst.Add("1");
lst.Add("2");
lst.Add("3");
lst.Add("4");
lst.Add("5");
MessageBox.Show(comboBox.SelectedIndex.ToString()); // -1
comboBox.IsTextSearchEnabled = false;
comboBox.ItemsSource = lst;
comboBox.Text = "3";
MessageBox.Show(comboBox.SelectedIndex.ToString()); // -1
I wonder if there is a way to achieve both (i.e disabling Auto Complete feature and still have ComboBox update its SelectedIndex automatically when its Text is changed)
There are several ways to reach it. In your case with strings it's enough to set not the Text property, but SelectedValue:
List<string> lst = new List<string>();
lst.Add("1");
lst.Add("2");
lst.Add("3");
lst.Add("4");
lst.Add("5");
MessageBox.Show(comboBox.SelectedIndex.ToString()); // -1
comboBox.IsTextSearchEnabled = false;
comboBox.ItemsSource = lst;
comboBox.SelectedValue = "3";
MessageBox.Show(comboBox.SelectedIndex.ToString()); // 2
If you have more complex data type as string, then you can set also SelectedValuePath or search it by yourself in ItemsSource in event handler for TextInput and set the ´SelectedItem´.
I have a DataTable that is coming from a Web Service, which I need to bind to a ComboBox. I have not grokked doing binding in XAML yet so this question is about binding in code instead. So far I have tried
cboManager.DataContext = Slurp.DistrictManagerSelect().DefaultView;
cboManager.DisplayMemberPath = "Name";
cboManager.SelectedValuePath = "NameListId";
cboManager.SetBinding(ComboBox.ItemsSourceProperty, new Binding());
And I have tried
DataTable tbl = new DataTable();
tbl = Slurp.DistrictManagerSelect();
cboManager.ItemsSource = ((IListSource)tbl).GetList();
cboManager.DisplayMemberPath = "[Name]";
cboManager.SelectedValuePath = "[NameListId]";
DataContext = this;
In both cases I get the list of managers to show but when I select from the ComboBox I get [Name] and [NameListId] and not the values I am expecting. What am I doing wrong (other than not using XAML's DataBinding)?
Edit added after answers to my original post came in.
So (based on Rachel's response) try number three looks like this:
using (DataTable tbl = Slurp.DistrictManagerSelect())
{
List<ManagerList> list = new List<ManagerList>();
foreach (var row in tbl.Rows)
{
list.Add(new ManagerList
{
NameListId = (int)row[0],
Name = row[1].ToString()
});
}
}
Assuming I am doing what she meant the correct way I am no getting this error Cannot apply indexing with [] to an expression of type 'object'
Have you tried to just bind to the DataTable directly? Do you have columns Name and NameListId? Leave off the DataContext (you already assigned the ItemsSource).
DataTable tbl = Slurp.DistrictManagerSelect();
cboManager.ItemsSource = tbl;
cboManager.DisplayMemberPath = "Name";
cboManager.SelectedValuePath = "NameListId";
When you cast to the IListSource I suspect it is combining all the columns. If you want to bind to a list then you need to create items that have properties Name and NameListID.
I think that's because your ItemsSource is a DataTable, so each ComboBoxItem contains a DataContext of a DataRow, and the DataRow class doesn't have properties called Name or NameListId
Basically, you're trying to tell the ComboBox to display DataRow.Name, and set the value to DataRow.NameListId, both of which are not valid properties.
I usually prefer to parse data into objects, and bind the ItemsSource a List<MyObject> or ObservableCollection<MyObject>
foreach(DataRow row in tbl.Rows)
list.Add(new MyObject { Name = row[0].ToString(), NameListId = (int)row[1] });
cboManager.ItemsSource = list;
I wanted a combo box in data grid which i added using the following code behind
DataColumn dc;
DataGridNS.DataGridTemplateColumn dgc = new DataGridNS.DataGridTemplateColumn();
dgc.Header = dc.ColumnName;
dgc.Width = 100;
dgc.IsReadOnly = true;
DataTemplate dtm = new DataTemplate();
FrameworkElementFactory outer = new FrameworkElementFactory(typeof(ComboBox));
dtm.VisualTree = outer;
dgc.CellTemplate = dtm;
dtgrdAtlas.Columns.Add(dgc);
i want to bind an array to this combo box.
how do i do that.
This code is in a seperate function where i add columns to data grid and my string array is in seperate function/class.
To bind a list to a ComboBox you need to set the ItemsSource, or Binding a List to the ItemsSource.
Here in this example I set directly the ItemsSource :
MyCombobox.ItemsSource = new List<int> {2, 3, 4 ,5, 6};
I have been confused while setting SelectedItem programmaticaly in wpf applications with Net Framework 3.5 sp1 installed. I have carefully read about hundred posts \topics but still confused((
My xaml:
<ComboBox name="cbTheme">
<ComboBoxItem>Sunrise theme</ComboBoxItem>
<ComboBoxItem>Sunset theme</ComboBoxItem>
</ComboBox>
If I add IsSelected="True" property in one of the items - it's dosn't sets this item selected. WHY ?
And i was try different in code and still can't set selected item:
cbTheme.SelectedItem=cbTheme.Items.GetItemAt(1); //dosn't work
cbTheme.Text = "Sunrise theme"; //dosn't work
cbTheme.Text = cbTheme.Items.GetItemAt(1).ToString();//dosn't work
cbTheme.SelectedValue = ...//dosn't work
cbTheme.SelectedValuePath = .. //dosn't work
//and even this dosn't work:
ComboBoxItem selcbi = (ComboBoxItem)cbTheme.Items.GetItemAt(1);//or selcbi = new ComboBoxItem
cbTheme.SelectedItem = selcbi;
The SelectedItem is not readonly property, so why it wan't work?
I think thats should be a Microsoft's problems, not my. Or I have missed something??? I have try playing with ListBox, and all work fine with same code, I can set selections, get selections and so on.... So what can I do with ComboBox ? Maybe some tricks ???
To select any item in the ComboBox and to set it as default item selected just use the below line:
combobox.SelectedIndex = 0; //index should be the index of item which you want to be selected
If i add the combobox and items programmatically, this works for me:
ComboBox newCombo = new ComboBox();
ComboBoxItem newitem = new ComboBoxItem();
newitem.Content = "test 1";
newCombo.Items.Add(newitem);
newitem = new ComboBoxItem();
newitem.Content = "test 2";
newCombo.Items.Add(newitem);
newitem = new ComboBoxItem();
newitem.Content = "test 3";
newCombo.Items.Add(newitem);
newCombo.SelectedItem = ((ComboBoxItem)newCombo.Items[1]);
newCombo.Text = ((ComboBoxItem)newCombo.Items[1]).Content.ToString();
newStack.Children.Add(newCombo);
It also works if it set the ItemSource property programmatically, then set the text to the selected value.
Create a public property in your viewmodel for the theme list and one for the selected item:
private IEnumerable<string> _themeList;
public IEnumerable<string> ThemeList
{
get { return _themeList; }
set
{
_themeList = value;
PropertyChangedEvent.Notify(this, "ThemeList");
}
}
private string _selectedItem;
public string SelectedItem
{
get { return _selectedItem; }
set
{
_selectedItem = value;
PropertyChangedEvent.Notify(this,"SelectedItem");
}
}
bind your combobox in xaml to the properties like this:
<ComboBox
Name="cbTheme"
ItemsSource="{Binding ThemeList}"
SelectedItem="{Binding SelectedItem}">
</ComboBox>
now all you do is add items to the ThemeList to populate the combobox. To select an item in the list, set the selected property to the text of the item you want selected like this:
var tmpList = new List<string>();
tmpList.Add("Sunrise theme");
tmpList.Add("Sunset theme");
_viewModel.ThemeList = tmpList;
_viewModel.SelectedItem = "Sunset theme";
or try setting the selected item to the string value of the item you want selected in your own code if you want to use the code you currently have - not sure if it will work but you can try.
If you know the index of the item you want to set, in this case it looks like you are trying to set index 1, you simply do:
cbTheme.SelectedIndex = 1;
I found that when you don't know the index, that's when you have the real issue. I know this goes beyond the original question, but for Googlers on that count that want to know how to set the item when the index isn't known but the value you want to display IS known, if you are filling your dropdown with an ItemSource from a DataTable, for example, you can get that index by doing this:
int matchedIndex = 0;
if (dt != null & dt.Rows != null)
{
if (dt.Rows.Count > 0)
{
foreach (DataRow dr in dt.Rows)
{
string myRowValue = dr["SOME_COLUMN"] != null ? dr["SOME_COLUMN"].ToString() : String.Empty;
if (myRowValue == "Value I Want To Set")
break;
else
matchedIndex++;
}
}
}
And then you do simply do cbTheme.SelectedIndex = matchedIndex;.
A similar iteration of ComboBoxItem items instead of DataRow rows could yield a similar result, if the ComboBox was filled how the OP shows, instead.
Is the ComboBox data bound?
If so you are probably better to do it through Binding rather than code ....
See this question ... WPF ListView Programmatically Select Item
Maybe create a new SelectableObject {Text = "Abc Theme", IsCurrentlySelected = True}
Bind a collection of SelectableObjects to the ComboBox.
Essentially setting the IsCurrentlySelected property in the model and having UI update from the Model.
Acording Answer 4
If you already add the Items in the Item source.
Fire the PropertyChangedEvent of the selectet Value.
tmpList.Add("Sunrise theme");
tmpList.Add("Sunset theme");
PropertyChangedEvent.Notify(this,"SelectedItem");