I was wondering about a way to get the keyboard strokes & read them. This windows api can be used from all sorts of keylogger hacking tricks to useful shortcut keys in an OS that you would like to define. here is a small code snippet with explanation:

This snippet shows the user how to get the key pressed. That is if the user presses control key that key is identified. Using this we can develop applications with greater flexibility. For example we can make an application to close if a key is pressed and so on.

This code is basically a smaller one with greater potential. It just contains three lines of code.

[codesyntax lang=”vbnet” highlight_lines=””]

Public Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer

[/codesyntax]

[codesyntax lang=”vbnet” highlight_lines=””]

On Error Resume Next
 'To check wheteher Control key is pressed
 If GetAsyncKeyState(17) Then
 msgbox "Control key pressed"
 End If

[/codesyntax]

One of my favorite .NET control is the ListView. It is very useful for displaying multiple records on a spreadsheet format. Column sorting is one the feature of spreadsheet applications that most of end-users are used to. Unfortunately, this is not readily available as property in VB.NET. The ListView Sorting property only sorts items and not the sub-items so it can’t be use if we want to allow the user to sort your list by any clicked column.

To make your ListView application capable of column sorting, follow these steps:

1. On your existing project, add a new class with following code:

[codesyntax lang=”vbnet” highlight_lines=””]

Imports System.Collections
Public Class clsListviewSorter
 Implements System.Collections.IComparer ' Implements a comparer Implements IComparer 
 Private m_ColumnNumber As Integer
 Private m_SortOrder As SortOrder
 Public Sub New(ByVal column_number As Integer, ByVal sort_order As SortOrder)
 m_ColumnNumber = column_number
 m_SortOrder = sort_order
 End Sub
 ' Compare the items in the appropriate column 
 Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements IComparer.Compare
 Dim item_x As ListViewItem = DirectCast(x, ListViewItem)
 Dim item_y As ListViewItem = DirectCast(y, ListViewItem)
 ' Get the sub-item values. 
 Dim string_x As String
 If item_x.SubItems.Count <= m_ColumnNumber Then
 string_x = ""
 Else
 string_x = item_x.SubItems(m_ColumnNumber).Text
 End If
 Dim string_y As String
 If item_y.SubItems.Count <= m_ColumnNumber Then
 string_y = ""
 Else
 string_y = item_y.SubItems(m_ColumnNumber).Text
 End If
 ' Compare them. 
 If m_SortOrder = SortOrder.Ascending Then
 If IsNumeric(string_x) And IsNumeric(string_y) Then
 Return (Val(string_x).CompareTo(Val(string_y)))
 ElseIf IsDate(string_x) And IsDate(string_y) Then
 Return (DateTime.Parse(string_x).CompareTo(DateTime.Parse(string_y)))
 Else
 Return (String.Compare(string_x, string_y))
 End If
 Else
 If IsNumeric(string_x) And IsNumeric(string_y) Then
 Return (Val(string_y).CompareTo(Val(string_x)))
 ElseIf IsDate(string_x) And IsDate(string_y) Then
 Return (DateTime.Parse(string_y).CompareTo(DateTime.Parse(string_x)))
 Else
 Return (String.Compare(string_y, string_x))
 End If
 End If
 End Function
End Class

[/codesyntax]

2. Declare a private variable on the form where the listview you want to be sorted is located.

[codesyntax lang=”vbnet” highlight_lines=””]

Private m_SortingColumn As ColumnHeader

[/codesyntax]

3. Then on the listview’s ColumnClick event, add the following code

[codesyntax lang=”vbnet” highlight_lines=””]

Private Sub ListView1_ColumnClick(ByVal sender As Object, ByVal e As System.Windows.Forms.ColumnClickEventArgs) Handles ListView1.ColumnClick
 ' Get the new sorting column. 
 Dim new_sorting_column As ColumnHeader = ListView1.Columns(e.Column)
 ' Figure out the new sorting order. 
 Dim sort_order As System.Windows.Forms.SortOrder
 If m_SortingColumn Is Nothing Then
 ' New column. Sort ascending. 
 sort_order = SortOrder.Ascending
 Else ' See if this is the same column. 
 If new_sorting_column.Equals(m_SortingColumn) Then
 ' Same column. Switch the sort order. 
 If m_SortingColumn.Text.StartsWith("> ") Then
 sort_order = SortOrder.Descending
 Else
 sort_order = SortOrder.Ascending
 End If
 Else
 ' New column. Sort ascending. 
 sort_order = SortOrder.Ascending
 End If
 ' Remove the old sort indicator. 
 m_SortingColumn.Text = m_SortingColumn.Text.Substring(2)
 End If
 ' Display the new sort order. 
 m_SortingColumn = new_sorting_column
 If sort_order = SortOrder.Ascending Then
 m_SortingColumn.Text = "> " & m_SortingColumn.Text
 Else
 m_SortingColumn.Text = "< " & m_SortingColumn.Text
 End If
 ' Create a comparer. 
 ListView1.ListViewItemSorter = New clsListviewSorter(e.Column, sort_order)
 ' Sort. 
 ListView1.Sort()
 End Sub

[/codesyntax]

There you have it, test your listview application and it should be sorting by the column clicked.