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POComboBox with progressive auto-complete
 

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    <p>We need to populate a combobox with data retrieved from a database. Because the number of potential records retrieved could be in the thousands, we limit the list by not even calling the database until the user has entered the first 5 characters in the combobox. Then the list is populated and progressively filtered as the user keys in additional characters using combobox.Items.Filter.</p> <p>The problem is that the process is not reversible. Let's say the user has entered 000-Test11 and what is being shown is 000-Test11 and 000-Test111. If the user hits backspace, the combobox should go back to 000-Test1 and show the above in addition to 000-Test12, 000-Test13, etc. </p> <p>The logic in the combobox text editor text changed event has been adapted from an MSDN thread - Implimenting AutoComplete combobox - Yiling Lai, Rovi Corporation answer: <a href="http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/cec1b222-2849-4a54-bcf2-03041efcf304/" rel="nofollow">http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/cec1b222-2849-4a54-bcf2-03041efcf304/</a>.</p> <p>Here is the code to demonstrate the issue we are having. </p> <p>StudyProxy class:</p> <pre><code> namespace WPFTesting { public class StudyProxy { public int StudyID { get; set; } public string StudyNumber { get; set; } public string Title { get; set; } public StudyProxy Init() { this.Title = this.StudyNumber; return this; } } } </code></pre> <p>The xaml:</p> <pre><code> &lt;Window x:Class="WPFTesting.SelectStudyScreen" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="300" Width="300" SizeToContent="WidthAndHeight"&gt; &lt;Grid&gt; &lt;DockPanel Height="250" Width="250"&gt; &lt;ComboBox DockPanel.Dock="Top" VerticalAlignment="Top" Name="comboBox1" IsEditable="True" IsReadOnly="False" Margin="10" DisplayMemberPath="StudyNumber" SelectedValuePath="StudyID" SelectionChanged="comboBox1_SelectionChanged"/&gt; &lt;DataGrid Name="dataGrid1" /&gt; &lt;/DockPanel&gt; &lt;/Grid&gt; &lt;/Window&gt; </code></pre> <p>The code behind:</p> <pre><code> using System; using System.Windows; using System.Collections.Generic; using System.Collections.ObjectModel; using System.Diagnostics; using System.Windows.Controls; using System.Windows.Input; using System.Windows.Controls.Primitives; using System.Runtime.Serialization; namespace WPFTesting { /// &lt;summary&gt; /// Interaction logic for SelectStudyScreen.xaml /// &lt;/summary&gt; public partial class SelectStudyScreen { private Popup _comboBox1Popup; private TextBox _comboBox1Editor; private StudyProxy _currentItem; public SelectStudyScreen() { InitializeComponent(); comboBox1.Loaded += new RoutedEventHandler(comboBox1_Loaded); } private void comboBox1_SelectionChanged(object sender, SelectionChangedEventArgs e) { if (comboBox1.SelectedIndex == -1) { dataGrid1.ItemsSource = null; } else { _currentItem = comboBox1.SelectedItem as StudyProxy; List&lt;string&gt; studyIDs = new List&lt;string&gt;(new string[] { comboBox1.SelectedValue.ToString() }); } } private void comboBox1_Loaded(object sender, RoutedEventArgs e) { _comboBox1Popup = comboBox1.Template.FindName("PART_Popup", comboBox1) as Popup; _comboBox1Editor = comboBox1.Template.FindName("PART_EditableTextBox", comboBox1) as TextBox; if (_comboBox1Editor != null) { _comboBox1Editor.KeyDown += new System.Windows.Input.KeyEventHandler(comboBox1Editor_KeyDown); _comboBox1Editor.TextChanged += new TextChangedEventHandler(comboBox1Editor_TextChanged); _comboBox1Editor.PreviewKeyDown += new KeyEventHandler(comboBox1Editor_PreviewKeyDown); } } void comboBox1Editor_PreviewKeyDown(object sender, KeyEventArgs e) { if (_comboBox1Editor.Text != comboBox1.Text) { } } void comboBox1Editor_KeyDown(object sender, System.Windows.Input.KeyEventArgs e) { } private void comboBox1Editor_TextChanged(object sender, TextChangedEventArgs e) { string text = (sender as TextBox).Text.Trim(); if (text.Length &lt; 5) { _comboBox1Popup.IsOpen = false; } else if (text.Length == 5) { _comboBox1Popup.IsOpen = false; comboBox1.ItemsSource = GetTestData(); } else { // Adapted // From: Implimenting AutoComplete combobox - Yiling Lai, Rovi Corporation answer // Link: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/cec1b222-2849-4a54-bcf2-03041efcf304/ comboBox1.Items.Filter += a =&gt; { if ((a as StudyProxy).StudyNumber.StartsWith(text, StringComparison.OrdinalIgnoreCase)) { return true; } return false; }; _comboBox1Popup.IsOpen = true; } } private List&lt;StudyProxy&gt; GetTestData() { List&lt;StudyProxy&gt; list = new List&lt;StudyProxy&gt;(); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test1" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test11" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test111" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test1111" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test12" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test122" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test1222" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test13" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test133" }.Init()); list.Add(new StudyProxy() { StudyID = 1, StudyNumber = "000-Test1333" }.Init()); return list; } } } </code></pre>
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    1. COYou wrote what you need. But what is happning with your code currently?
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    2. COSorry, when the combobox's ItemsSource is set, the first matching item is highlighted and the list is dropped. As you continue to type, the list gets smaller and smaller until only 1 item remains. This is what is desired. But if you hit the backspace key, it does not go back to the previous filter which would show additional items (eg once you show 000-Test111 you cannot get back to 000-Test11).
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    3. CODoes comboBox1Editor_TextChanged not even get called with a backspace key?
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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