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Posted 2 Jun 2012

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Filtered DropDown ComboBox

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2 Jun 2012CPOL
A rather quick and dirty way of creating a filtered combo box in WPF.

I have discovered a rather quick and dirty way of creating a filtered combo box in WPF. It has some quirks, but it is good for longer lists. One issue I discovered was that if I was using the same list for two combo boxes they would interfere with one another. Here is the code behind to handle with combo box:

comboBox1.Loaded += delegate
  var textBox1 = (TextBox)comboBox1.Template.FindName(
    "PART_EditableTextBox", comboBox1);
  var popup1 = (Popup)comboBox1.Template.FindName("PART_Popup", comboBox1);

  textBox1.TextChanged += delegate
    popup1.IsOpen = true;
    comboBox1.Items.Filter += a =>
      return textBox1.Text.Length == 0 || (a.ToString().ToUpper().
        Substring(0, Math.Max(textBox1.SelectionStart, 1)).ToUpper()));

In the example I have two combo boxes because I needed two and I was getting some strange behavior between the two. Still get some strange behavior that somebody may be able to figure out.

To do two text boxes I have duplicated code for the lambda expressions. I needed to do this because need to have the parent combo box information when dealing with the TextChanged event. I was unable to figure out how to not duplicate code without some side effects.

The XAML for the form is the following:

<Window x:Class="FilteredComboBoxExample.MainWindow"
        Title="Filtered DropDown ComboBox" Height="200" Width="200">
    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center" Width="80">
    <ComboBox Grid.Column="2"
              ItemsSource="{Binding Source={x:Static local:StaticData.GetList}}" />
    <ComboBox Grid.Column="2"
              ItemsSource="{Binding Source={x:Static local:StaticData.GetList}}" />


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Software Developer (Senior) Clifford Nelson Consulting
United States United States
Has been working as a C# developer on contract for the last several years, including 3 years at Microsoft. Previously worked with Visual Basic and Microsoft Access VBA, and have developed code for Word, Excel and Outlook. Started working with WPF in 2007 when part of the Microsoft WPF team. For the last eight years has been working primarily as a senior WPF/C# and Silverlight/C# developer. Currently working as WPF developer with BioNano Genomics in San Diego, CA redesigning their UI for their camera system. he can be reached at

Comments and Discussions

SuggestionArticle is not very useful in this shape Pin
WojciechD9-Oct-14 0:41
professionalWojciechD9-Oct-14 0:41 
QuestionIssues Pin
Guillaume Leparmentier3-Jun-12 0:44
Guillaume Leparmentier3-Jun-12 0:44 

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