Multiple Columns in WPF ListBox

In this article we will discuss ways to have multiple columns in WPF ListBox control and layout the ListBox such that each row has 3 items. All WPF controls deriving from ItemsControl provide an ItemsPanel property that allows us to replace the internal layout panel that arranges the items. So to have multiple columns in a ListBox we have to change the ItemsPanel property of the control.

WrapPanel

One of the most simple way of displaying content horizontally in ListBox is to have WrapPanel in ItemsPanel property of Listbox. But if we need to display fixed number of items in a row then we have to disable the horizontal scrollBar so that item get wrap to next row and set fixed width for ListBox. But as item get wrap the ListBoxItem are not positioned uniformly. So we have to set Width for each ListBoxItem so that all the items are positioned in a tabular way.

        <ListBox Width="300" ScrollViewer.HorizontalScrollBarVisibility="Disabled">
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <WrapPanel Orientation="Horizontal"/>
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            
            <ListBoxItem Content="Visual Basic" Width="80"/>
            <ListBoxItem Content="Silverlight" Width="80"/>
            <ListBoxItem Content="ASP.NET" Width="80"/>
            <ListBoxItem Content="WCF" Width="80"/>
            <ListBoxItem Content="Web Services" Width="80"/>
            <ListBoxItem Content="Windows Service" Width="80"/>
        </ListBox>

UniformGrid

One of the drawback with WrapPanel was we had to disable horizontal scrollbar, set Width for ListBox and also width for ListBoxItem. So we can use UniformGrid instead of WrapPanel in ItemsPanel property and set Columns property of it to the number of items we need to display in a row. Using UniformGrid all the items in the ListBox will have same width and height.

        <ListBox>
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <UniformGrid Columns="3"/>
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>
            
            <ListBoxItem Content="Visual Basic" />
            <ListBoxItem Content="Silverlight" />
            <ListBoxItem Content="ASP.NET" />
            <ListBoxItem Content="WCF" />
            <ListBoxItem Content="Web Services" />
            <ListBoxItem Content="Windows Service" />
        </ListBox>

Grid

Although UniformGrid is the best solution for multiple column ListBox but sometime we don’t want all the columns in the ListBox of same size. Also in some scenario we could have a requirement where we need to merge two or more columns (or rows) for a larger text. In this situation using Grid is very useful option.

        <ListBox>
            <ListBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="*"/>
                            <RowDefinition Height="*"/>
                            <RowDefinition Height="*"/>
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="0.8*"/>
                            <ColumnDefinition Width="*"/>
                            <ColumnDefinition Width="Auto"/>
                        </Grid.ColumnDefinitions>
                    </Grid>
                </ItemsPanelTemplate>
            </ListBox.ItemsPanel>

            <ListBoxItem Content="WCF"  Grid.Row="0" Grid.Column="0"/>
            <ListBoxItem Content="ASP.NET"  Grid.Row="0" Grid.Column="1"/>
            <ListBoxItem Content="VB.NET" Grid.Row="0" Grid.Column="2"/>
            <ListBoxItem Content="Silverlight" Grid.Row="1" Grid.Column="0"/>
            <ListBoxItem Content="Web Services" Grid.Row="1" Grid.Column="1"/>
            <ListBoxItem Content="Windows Service" Grid.Row="1" Grid.Column="2"/>
            <ListBoxItem Content="Windows Presentation Foundation" Grid.Row="2" Grid.ColumnSpan="3"/>
        </ListBox>

Only headache of using Grid in ItemsPanel is that we have to set RowDefinitions and ColumnDefinitions for the Grid. Also we have to set the Grid.Row and Grid.Column for each item to position them in the ListBox. But in some scenario as described above it is very useful.

I unlock Joy

At the recent Mobile Developer Summit which took place on November 2, 2011 at Bangalore Microsoft announced the details of the developer programme for Windows Mobile in India with ‘I unlock Joy’, a unique Application Development and Submission Program, where technology professionals and students get an opportunity to develop applications and showcase creativity.

‘I unlock Joy’ programme for developers has started from November 1, 2011 and will continue till June 30, 2012 whereas the program for students will begin on December 18, 2011 and conclude on March 30 next year.

Developer competitive categories:

· “SUBMIT & WIN” CATEGORY: A registered participant submits THREE qualified Windows Phone Application in the Marketplace and gets a chance to win a Windows Phone. In this category, the Applications must be distinct and of non-trivial utility value for the Application User.

· “PORT 2 APPS & WIN” CATEGORY: A registered participant submitting TWO qualified Windows Phone Applications in the Marketplace which are ported from existing Android or iPhone Applications get to win a Windows Phone.

· “WOMEN SPECIAL” CATEGORY: A first of its kind in the developer space. The first 100 registered Woman Developers who submit ONE (1) qualified Windows Phone Application each in the Marketplace qualify to win a Windows Phone each. The applications can be based on Entertainment, Fashion, Leisure, Sports, Recreation or Travel themes.

Student competitive categories:

· “STUDENT” CATEGORY: Calling on the community to be a part of the initiative, the “I unlock Joy” programme is customized to unfold their innovative and creative best and become among the select first few proud owners of the Windows Phone.

The contestants need to build one or more applications using Dev Tools and submit on AppHub. If their apps get certified and published on the Windows Phone Marketplace during the contest period which ends November 18, they can claim goodies like a brand new Windows Phone, certificate of acknowledgment from Microsoft and Windows Phone T-Shirts as well as USB flash drives.

You can find more information from official Website

http://www.microsoft.com/india/iunlockjoy/

WPF Collapsible Panel

In this article I have describe way to create a collapsible panel in WPF. This is one of the most common questions asked by many developers. Collapsible Panel can be used by user to collapse the content which he doesn't want to use and see only core information and hence keep the screen clean.

This sample inherits the Expander control which is available in WPF. It support panel collapse in all the four directions (left, right, top and bottom).

public class CollapsiblePanel : Expander
{
static CollapsiblePanel()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(CollapsiblePanel), new FrameworkPropertyMetadata(typeof(CollapsiblePanel)));
}
}

Here is the XAML for CollapsiblePanel

<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:sys="clr-namespace:System;assembly=mscorlib" 
xmlns:local="clr-namespace:CollapsiblePanelDemo">

<local:MultiplyConverter x:Key="multiplyConverter" />

<Style x:Key="ExpanderHeaderFocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Border>
<Rectangle SnapsToDevicePixels="true" Margin="0" Stroke="Black" StrokeDashArray="1 2" StrokeThickness="1" />
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

<Style x:Key="ExpanderUpHeaderStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Padding="{TemplateBinding Padding}">
<Grid Background="Transparent" SnapsToDevicePixels="False">
<Grid.LayoutTransform>
<RotateTransform Angle="90"/>
</Grid.LayoutTransform>


<Path x:Name="trapazoid" Fill="{Binding Path=Background, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}"  HorizontalAlignment="Center"   VerticalAlignment="Center">
<Path.Data>
<PathGeometry>
<PathGeometry.Figures>
<PathFigure StartPoint="0,0" >
<PathFigure.Segments>

<ArcSegment Size="25,25" RotationAngle="45" IsLargeArc="False" SweepDirection="Clockwise" Point="0,48"/>

</PathFigure.Segments>
</PathFigure >
</PathGeometry.Figures>
</PathGeometry>
</Path.Data>
</Path>



<Path x:Name="arrow" Data="M 1,1.5 L 9,9 L 1,16 1, 1" HorizontalAlignment="Center" SnapsToDevicePixels="false" Fill="{Binding Path=BorderBrush, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}" StrokeThickness="2" VerticalAlignment="Center"/>

</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="true">
<Setter Property="Data" TargetName="arrow" Value="M 9,1 L 1,8 L 9,16, 9,1"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

<Style x:Key="ExpanderLeftHeaderStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Padding="{TemplateBinding Padding}">
<Grid Background="Transparent" SnapsToDevicePixels="False">



<Path x:Name="trapazoid" Fill="{Binding Path=Background, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}"  HorizontalAlignment="Center"   VerticalAlignment="Center">
<Path.Data>
<PathGeometry>
<PathGeometry.Figures>
<PathFigure StartPoint="0,0" >
<PathFigure.Segments>

<ArcSegment Size="25,25" RotationAngle="45" IsLargeArc="False" SweepDirection="Clockwise" Point="0,48"/>

</PathFigure.Segments>
</PathFigure >
</PathGeometry.Figures>
</PathGeometry>
</Path.Data>
</Path>
<Path x:Name="arrow" Data="M 1,1.5 L 9,9 L 1,16 1, 1" HorizontalAlignment="Center" SnapsToDevicePixels="false" Fill="{Binding Path=BorderBrush, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}" StrokeThickness="2" VerticalAlignment="Center"/>

</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="true">
<Setter Property="Data" TargetName="arrow" Value="M 9,1 L 1,8 L 9,16, 9,1"/>
</Trigger>

</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

<Style x:Key="ExpanderRightHeaderStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Padding="{TemplateBinding Padding}">
<Grid Background="Transparent" SnapsToDevicePixels="False">
<Grid.LayoutTransform>
<RotateTransform Angle="180"/>
</Grid.LayoutTransform>

<Path x:Name="trapazoid" Fill="{Binding Path=Background, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}"  HorizontalAlignment="Center"   VerticalAlignment="Center">
<Path.Data>
<PathGeometry>
<PathGeometry.Figures>
<PathFigure StartPoint="0,0" >
<PathFigure.Segments>

<ArcSegment Size="25,25" RotationAngle="45" IsLargeArc="False" SweepDirection="Clockwise" Point="0,48"/>

</PathFigure.Segments>
</PathFigure >
</PathGeometry.Figures>
</PathGeometry>
</Path.Data>
</Path>
<Path x:Name="arrow" Data="M 1,1.5 L 9,9 L 1,16 1, 1" HorizontalAlignment="Center" SnapsToDevicePixels="false" Fill="{Binding Path=BorderBrush, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}" StrokeThickness="2" VerticalAlignment="Center"/>

</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="true">
<Setter Property="Data" TargetName="arrow" Value="M 9,1 L 1,8 L 9,16, 9,1"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

<Style x:Key="ExpanderDownHeaderStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Padding="{TemplateBinding Padding}">
<Grid Background="Transparent" SnapsToDevicePixels="False">
<Grid.LayoutTransform>
<RotateTransform Angle="-90"/>
</Grid.LayoutTransform>


<Path x:Name="trapazoid" Fill="{Binding Path=Background, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}"  HorizontalAlignment="Center"   VerticalAlignment="Center">
<Path.Data>
<PathGeometry>
<PathGeometry.Figures>
<PathFigure StartPoint="0,0" >
<PathFigure.Segments>

<ArcSegment Size="25,25" RotationAngle="45" IsLargeArc="False" SweepDirection="Clockwise" Point="0,48"/>

</PathFigure.Segments>
</PathFigure >
</PathGeometry.Figures>
</PathGeometry>
</Path.Data>
</Path>
<Path x:Name="arrow" Data="M 1,1.5 L 9,9 L 1,16 1, 1" HorizontalAlignment="Center" SnapsToDevicePixels="false" Fill="{Binding Path=BorderBrush, RelativeSource={RelativeSource FindAncestor, AncestorType=local:CollapsiblePanel}}" StrokeThickness="2" VerticalAlignment="Center"/>

</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="true">
<Setter Property="Data" TargetName="arrow" Value="M 9,1 L 1,8 L 9,16, 9,1"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

<Style TargetType="{x:Type local:CollapsiblePanel}">
<Setter Property="Background" Value="LightGray"/>
<Setter Property="BorderBrush" Value="White"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Expander}">
<Border SnapsToDevicePixels="true">
<DockPanel>

<ToggleButton x:Name="HeaderSite" ContentTemplate="{TemplateBinding HeaderTemplate}" ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}" Content="{TemplateBinding Header}" DockPanel.Dock="Top" Foreground="{TemplateBinding Foreground}" FontWeight="{TemplateBinding FontWeight}" FocusVisualStyle="{StaticResource ExpanderHeaderFocusVisual}" FontStyle="{TemplateBinding FontStyle}" FontStretch="{TemplateBinding FontStretch}" FontSize="{TemplateBinding FontSize}" FontFamily="{TemplateBinding FontFamily}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" IsChecked="{Binding IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" Margin="0" MinWidth="0" MinHeight="0" Padding="{TemplateBinding Padding}" Style="{StaticResource ExpanderDownHeaderStyle}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>


<Grid  
x:Name="ExpandSiteContainer"  
Visibility="Visible"  
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"  
Margin="{TemplateBinding Padding}"  
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"  
DockPanel.Dock="Bottom"                                        
>

<Grid.Tag>
<sys:Double>0.0</sys:Double>
</Grid.Tag>
<ScrollViewer  
VerticalScrollBarVisibility="Hidden"  
HorizontalScrollBarVisibility="Hidden"  

>
<ContentPresenter  
x:Name="ExpandSite"  
Focusable="false"  
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}"  VerticalAlignment="{TemplateBinding VerticalContentAlignment}" 
>
</ContentPresenter>
</ScrollViewer>
</Grid>
</DockPanel>
</Border>
<ControlTemplate.Triggers>

<Trigger Property="IsExpanded" Value="true">
<Trigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName ="ExpandSiteContainer"   
Storyboard.TargetProperty ="Tag"  
To="1.0" Duration ="0:0:0.45" />
</Storyboard>
</BeginStoryboard>
</Trigger.EnterActions>
<Trigger.ExitActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName ="ExpandSiteContainer"   
Storyboard.TargetProperty ="Tag"  
To="0" Duration ="0:0:0.45"/>
</Storyboard>
</BeginStoryboard>
</Trigger.ExitActions>
</Trigger>

<Trigger Property="ExpandDirection" Value="Down">
<Setter Property="Height" TargetName="ExpandSiteContainer">
<Setter.Value>
<MultiBinding Converter="{StaticResource multiplyConverter}">
<Binding Path="ActualHeight" ElementName="ExpandSite"/>
<Binding Path="Tag" RelativeSource="{RelativeSource Self}" />
</MultiBinding>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="ExpandDirection" Value="Right">
<Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Right"/>
<Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Left"/>
<Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderRightHeaderStyle}"/>
<Setter Property="Width" TargetName="ExpandSiteContainer">
<Setter.Value>
<MultiBinding Converter="{StaticResource multiplyConverter}">
<Binding Path="ActualWidth" ElementName="ExpandSite"/>
<Binding Path="Tag" RelativeSource="{RelativeSource Self}" />
</MultiBinding>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="ExpandDirection" Value="Up">
<Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Top"/>
<Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Bottom"/>
<Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderUpHeaderStyle}"/>
<Setter Property="Height" TargetName="ExpandSiteContainer">
<Setter.Value>
<MultiBinding Converter="{StaticResource multiplyConverter}">
<Binding Path="ActualHeight" ElementName="ExpandSite"/>
<Binding Path="Tag" RelativeSource="{RelativeSource Self}" />
</MultiBinding>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="ExpandDirection" Value="Left">
<Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Left"/>
<Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Right"/>
<Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderLeftHeaderStyle}"/>
<Setter Property="Width" TargetName="ExpandSiteContainer">
<Setter.Value>
<MultiBinding Converter="{StaticResource multiplyConverter}">
<Binding Path="ActualWidth" ElementName="ExpandSite"/>
<Binding Path="Tag" RelativeSource="{RelativeSource Self}" />
</MultiBinding>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>

</Style>
</ResourceDictionary>

Following is the example of using CollapsiblePanel control in WPF.

<my:CollapsiblePanel Grid.Row="2" Grid.Column="1" Header="Toolbar Demo" ExpandDirection="Down" x:Name="Expander2" BorderBrush="Yellow" Background="{StaticResource ToggleButtonBrush}" IsExpanded="False">
<my:CollapsiblePanel.Content>
<Image Source="/CollapsiblePanelDemo;component/Images/Koala.jpg" Height="240"  Stretch="Fill"   />
</my:CollapsiblePanel.Content>
</my:CollapsiblePanel>

You can download complete source code from following link
Download Source Code

Encrypt & Serialize an object

Serialization can be defined as the process of storing the state of an object instance to a storage medium. During this process, the public and private fields of the object and the name of the class, including the assembly containing the class, is converted to a stream of bytes, which is then written to a data stream. When the object is subsequently deserialized, an exact clone of the original object is created.

But many of the time we need to encrypt the object before saving it in the file, database, etc to protect from misuse. So we have first serialize the object into bytes and then we can encrypt the bytes using Cryptography.

Below is the code snippet to encrypt/decrypt the object in VB.net. Key in the code snippet is like a password which should be same during encryption and decryption.

Encrypt Code

Public Function Encrypt(Of T)(ByVal value As T, ByVal key As String) As Byte()

        Using strm As New MemoryStream
            Dim crypt As New TripleDESCryptoServiceProvider
            Dim slt() As Byte = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}
            Dim pdb As New Rfc2898DeriveBytes(key, slt)
            Dim bytDerivedKey() As Byte = pdb.GetBytes(24)
            crypt.Key = bytDerivedKey
            crypt.IV = pdb.GetBytes(8)

            Using cstream As New CryptoStream(strm, crypt.CreateEncryptor, CryptoStreamMode.Write)
                Dim bFormatter As New BinaryFormatter
                bFormatter.Serialize(cstream, value)
                cstream.Close()
                strm.Close()
            End Using

            Return strm.ToArray
        End Using
    End Function

Decrypt Code

Public Function Decrypt(Of T)(ByVal bytes() As Byte, ByVal key As String) As T
        Dim value As T

        Using strm As New MemoryStream(bytes)
            Dim crypt As New TripleDESCryptoServiceProvider
            Dim slt() As Byte = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}
            Dim pdb As New Rfc2898DeriveBytes(key, slt)
            Dim bytDerivedKey() As Byte = pdb.GetBytes(24)
            crypt.Key = bytDerivedKey
            crypt.IV = pdb.GetBytes(8)

            Using cstream As New CryptoStream(strm, crypt.CreateDecryptor, CryptoStreamMode.Read)
                Dim bFormatter As New BinaryFormatter
                value = bFormatter.Deserialize(cstream)
                cstream.Close()
                strm.Close()
            End Using
        End Using
        Return value
    End Function

Example to use above functions

<Serializable()>
    Public ClassCustomer
       Public PropertyCustomerID As Integer
        Public PropertyCustomerName As String
    End Class

    Private Sub SaveCustomer()
        Dim d As New Customer
        d.CustomerID = 1
d.CustomerName = "GAURAV"
        Dim bytes() As Byte = Encrypt(Of Customer)(d, "54321")
        My.Computer.FileSystem.WriteAllBytes("E:\Test.dat", bytes, False)
    End Sub

    Private Sub LoadCustomer()
        Dim bytes() As Byte = My.Computer.FileSystem.ReadAllBytes("E:\Test.dat")
        Dim objCustomer As Customer = Decrypt(Of Customer)(bytes, "54321")
    End Sub

ProcessCmdKey in Windows Form

Many time we need to trap the key pressed in Windows Form and based on it perform some operation. For example, stop user from closing the application when user press Alt+F4. Or want to stop user from moving from one child form to another child in a mdi form using Ctrl+Tab or stop user from moving from one tabpage to another tabpage in TabControl control. In this case ProcessCmdKey method is the best option.

ProcessCmdKey is a method in .NET which process the command key. This method is called during message preprocessing to handle command keys. Command keys are keys that always take precedence over regular input keys. The method return true to indicate that it has processed the command key, or false to indicate that the key is not a command key. This method is only called when the control is hosted in a Windows Forms application or as an ActiveX control.

The following example with stop user from closing the form when user press Alt+F4 and also stop user from navigate to another tabpage or child form by using Ctrl+Tab.

    Public Class Form1
        Protected Overrides Function ProcessCmdKey(ByRef msg As Message, ByVal keyData As Keys) As Boolean
            If keyData = (Keys.Alt Or Keys.F4) Then
                Return True
            ElseIf keyData = (Keys.Control Or Keys.Tab) Then
                Return True
            Else
                Return MyBase.ProcessCmdKey(msg, keyData)
            End If
        End Function
    End Class

Programmically toggling capslock button

VB.NET doesn’t contain any function through which we can On/Off capslock button in the keyboard. VB.NET has one function called My.Computer.Keyboard.CapsLock but it is readonly so we cannot change it. Capslock key also cannot be toggled by using SendKeys,Send() method. So only way to toggle the capslock key is by using WinAPIs. There is a function called keybd_event which can toggle the capslock key

Private Declare Sub keybd_event Lib "user32" (ByVal key As Byte, ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo As Long)

    Private Sub ToggleCapslock()
        keybd_event(Keys.Capital, 0, 0, 0)
        keybd_event(Keys.Capital, 0, &H2, 0)
    End Sub

In the above example we have called the keybd_event function twice. First for Keydown and second time for KeyUp (&H2 is value for KeyUp). If we want the code to work only to set capslock Off then we can change the code as below

   Private Sub SetCapslockOff()
If My.Computer.Keyboard.CapsLock = True Then
keybd_event(Keys.Capital, 0, 0, 0)
keybd_event(Keys.Capital, 0, &H2, 0)
Else
'Already off
End If
End Sub

Tab key work as an Enter key in Datagridview

To make the Tab key work as Enter key, we have to inherit DataGridView controls and override two methods ProcessDataGridViewKey and ProcessDialogKey. In both the methods if the user has click Tab then we have to ProcessEnterKey of Datagridview.

Public Class NewDataGridView
Inherits DataGridView

Protected Overrides Function ProcessDataGridViewKey(ByVal e As System.Windows.Forms.KeyEventArgs) As Boolean
If e.KeyCode = Keys.Tab Then
Me.ProcessEnterKey(e.KeyData)
Return True
End If
Return MyBase.ProcessDataGridViewKey(e)
End Function

Protected Overrides Function ProcessDialogKey(ByVal keyData As System.Windows.Forms.Keys) As Boolean
If keyData = Keys.Tab Then
Me.ProcessEnterKey(keyData)
Return True
End If
Return MyBase.ProcessDialogKey(keyData)
End Function
End Class