In this article I am going to show AutoCompleteTextBox in WPF. AutoCompleteTextBox mean when
we type something to search in a textbox to get a small list of valid
search results that match the search string entered so far. In this
article I am using Linq to Sql also. I have saved my DataBase inside
DATA folder. To run the application just add this database and change
connection string from setting inside properties folder.
See in this image.

Image 1.
Just change here DataSource according to you server name.
This is my DataTable from which records are coming.
Image 2.
This is my XAML code.
<Window x:Class="AutoCompleteTextBoxInWPF.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="250" Width="350">
<Grid Background="AliceBlue">
<Grid.RowDefinitions>
<RowDefinition Height="40" />
<RowDefinition Height="203" />
</Grid.RowDefinitions>
<TextBlock Text="Search :" HorizontalAlignment="Left"
VerticalAlignment="Bottom" Width="70" Height="15.96" Margin="31,0,0,4" />
<TextBox HorizontalAlignment="Right" VerticalAlignment="Bottom"
Height="25" Width="160" Margin="0,0,10,0" x:Name="txtName" TextWrapping="NoWrap" SelectionChanged="txtName_SelectionChanged" />
<ListBox x:Name="listName" SelectionChanged="listName_SelectionChanged"
Background="LightCyan" Grid.Row="1" Visibility="Collapsed"
HorizontalAlignment="Right" VerticalAlignment="Top" Width="160" Margin="0,0,10,0"/>
</Grid>
</Window>
When we run the application and want to search name which start with "R".

Image 3.
If we type character "E", then the textbox will show all names starting with this character.
Image 4.