<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="WpfApplication1.Window1" Title="ColumnDefinitions Sample"> <Border BorderBrush="Black" Background="White" BorderThickness="2"> <DockPanel Margin="10,0,0,0"> <TextBlock FontSize="20" FontWeight="Bold" DockPanel.Dock="Top">Grid Column and Row Collections</TextBlock> <Grid DockPanel.Dock="Top" HorizontalAlignment="Left" Name="grid1" ShowGridLines="true" Width="625" Height="400"> <Grid.ColumnDefinitions> <ColumnDefinition/> <ColumnDefinition/> <ColumnDefinition/> </Grid.ColumnDefinitions> <Grid.RowDefinitions> <RowDefinition/> <RowDefinition/> <RowDefinition/> </Grid.RowDefinitions> </Grid> <StackPanel HorizontalAlignment="Left" Orientation="Horizontal" Width="625" DockPanel.Dock="Top"> <Button Width="125" Click="addCol">Add Column</Button> </StackPanel> </DockPanel> </Border> </Window> //File:Window.xaml.cs using System; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; namespace WpfApplication1 { public partial class Window1 : Window { RowDefinition rowDef1; ColumnDefinition colDef1; private void addCol(object sender, RoutedEventArgs e) { colDef1 = new ColumnDefinition(); grid1.ColumnDefinitions.Add(colDef1); } } }