ListBox Deselect Tip

In ListBox, I've found that we can not deselect a entry once we selected any one of the entry in the list, even selecting no entry area. But I've found one of the solution to fix this issue as :
Let lstBox be the listbox in a form then,

Private Sub lstBox_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lstBox.MouseDown
Try
If Not lstBox.SelectionMode = SelectionMode.None Then
lstBox.SelectedIndex = lstBox.IndexFromPoint(e.X, e.Y)
End If
If (Windows.Forms.Control.ModifierKeys And Keys.Control) <> 0 Then
If lstBox.SelectedIndex = lstBox.IndexFromPoint(e.X, e.Y) Then
LstbIMBoxList.SelectedIndex = -1
End If
End If

Catch ex As Exception
'
End Try
End Sub

This may fix the issue in many situations depending on the requirements.

Singleton class

 Public Class MySingletonCls

           Private Shared objSingle As MySingletonCls
           Private Shared bIsCreated As Boolean

           Private Sub New()
               'Override the default constructor
           End Sub

           Public Shared Function CreateInstance() As MySingletonCls
                If bIsCreated = False Then
                   objSingle = New MySingletonCls()
                   bIsCreated = True
                   Return objSingle
               Else
                   Return objSingle
               End If
           End Function
 End Class

Tip to fetch XML using LINQ

Function FetchXML(ByVal url As Uri) As XElement

Dim x = WebRequest.Create(url)

Using r = x.GetResponse, rs As New StreamReader(r.GetResponseStream)

Return XElement.Parse(rs.ReadToEnd)

End Using

End Function

Call the function with the location of the xml file to get the corresponding XML element, that can be used for needed purpose.

Tip to handle XML based info project

Many times we need to manage the projects that just process specific information. Like if we consider a project that handles information about student(name,rno,course,class). So each student will have this information. To very easy way, if we create an XML file with one of the student. Creating a xml with this info is not very tough job.
Upto this point, half is done. Now we just need to get a class which can carry this information for various purposes and which can be written directly to xml file and also can read data from xml file( easiest way is serialize/deserialize mechanism can be very useful)

Now to get exact class that can be serialized directly to xml can be easily obtained from xsd utility of Visual Studio. just open the Visual Studio Command Prompt, and get the xsd file for your xml file and then convert this file directly to required class file. So the steps that can be needed to get the class are as below:

1. Create xml file say 'MyXml.xml'
2. run xsd MyXml.xml, will result MyXml.xsd
3. run xsd MyXml.xsd /c /l:vb, will result MyXml.vb

[the class can be constructed in various ways by using xsd, for details refer xsd documentation.]

note, in step 2 and 3, if current directory for running the command is same that is containing the MyXml.xml file then use command as such, else specify the full path of the file(s). Also target for the resulting file also can be specified(refer xsd documentation).

now we are with a class for which an object can be easily serialized/deserialized. So create collection of objects to carry all the records, applly any type of manipulations and serialize with XMLSerializer to write it to xml directly without worring about most of the validations as most are handled by serializers.

Protecting Assembly/DLL from illegal access tips

Sometimes we want to protect the access to the various functions of our assembly, I have identified that if the functions of the assembly made as friend and assembly is also made friend assembly, then the results will be as desired. As

A friend assembly is an assembly that is permitted to access another assembly's Friend types and members.

So Its possible to protect illegal access to our secure functionality.

This is one of the solution that can be helpful in some situation.

The info of Friend Assemblies can found at the link http://msdn.microsoft.com/en-us/library/bb384772.aspx

Some Simple LINQ Examples for existing examples

Here are some simple examples to understand better to LINQ

creating an iterator that will give you the letters "a" to "z" as you enumerate it:
Dim letters(0 To 25) As Char
For i As Int32 = 0 To 25
  letters(i) = ChrW(&H61 + i)
Next

By Using LINQ
Dim letters = From i In Enumerable.Range(0, 26) _
  Select ChrW(&H61 + i)
To read from a stream line-by-line,
search for a substring, and return the first couple of matches.
strLine = myStreamReader.ReadLine
Do While strLine IsNot Nothing
  If strLine.Contains(value) Then
     count += 1
     resultList.Add(strLine)
     If count >= 3 Then Exit Do
  End If
  strLine = myStreamReader.ReadLine
Loop

Unfortunately, StreamReader doesn't have an
iterator that returns each line. Without something that is enumerable,
you can't form the basis of a LINQ query, so you're forced to write
your query imperatively. That's not as bad as it might first sound;
Building the query into the imperative procedural block does work,
although it's kind of on the ugly side.
If you have an extension method named Lines that
returns an IEnumerable with each item a line, then you can create a
query like this:

Dim result = From line In myStreamReader.Lines _
   Where line.Contains(value) _
   Take 3

Tip for Alphablended area of image in list view

In List View, while displaying the images for the various files/folders, sometimes we face the problem that the alpha blended area of the image is not displayed properly with the default configuration of the list view. So to show the image with the correct display, I've found that if we set the ColorDepth of the image list (to be used to store the images to be shown in list view) to appropriate values, it provides the results as desired. So if smallImgLst and largeImgLst are the two image lists used for list view then if we need two views of the list i.e. Small images(16x16) and Large imges(32x32) then we can set the values as below:

smallImgLst.ColorDepth=ColorDepth.Depth32Bit
largeImgLst.ColorDepth=ColorDepth.Depth32Bit

smallImgLst.ImageSize=New System.Drawing.Size(16,16)
largeImgLst.ImageSize=New System.Drawing.Size(32,32)

If there are some other tips to resolve such kind of issue then comments are invited for discussion.

Display Image in ComboBox

In case we need to display a list of images in ComboBox we can do it by caring just few things about combobox. Firtsly set the 'DrawMode' of the ComboBox to 'OwnerDrawFixed' if all the images are of same size or set 'OwnerDrawVariable' if images are of variable size. and also for the variable sized images set the width and height during the 'MeasureItem' event of the combobox. If imgList1 contains all the needed images of variable and let number of items in the combobox is equal to number of images in the imagelist and each index of image specifies the corresponding item in combo box, Then I guess the following will be fine to get the list of images in the combobox.

1. Set the property 'DrawMode' to OwnerDrawVariable
2. In the method that implement event 'DrawItem' of the combo box, for the case if index of current item is non empty then then draw the image. i.e.

If e.Index<>-1 Then
e.Graphics.DrawImage(imgList1.images(e.Index),e.Bounds.Left,e.Bounds.Top)
End If

3. In the method that implements the 'MeasureItem' event of the combo box the following can be used
e.ItemHeight =imgList1.ImgaeSize.Height
e.ItemWidth = imgList1.ImageSize.Width


These are the basic settings that are needed to display images in combo box, rest are depends on the requirements.

Drop the lines if you think that can be help better for similar kind of requirements.

Count Character Occurances In a String

In a string occurance of particular character can be found easily by using the function 'InStr()' which returns the location of the character in the string. But if we want to count the number of occurances of particular character in the string then I've found the following three ways to get the

Private Function countOccurance1(ByVal hayStack As String,ByVal needle As Char) As Integer

If String.IsNullOrEmpty(hayStack) Then Return 0
Dim chars() As Char = hayStack.ToCharArray
Dim count As Integer = 0
For Each ch As Char In chars
If ch = needle Then count += 1
Next
Return count

End Function

Private Function countOccurance2(ByVal hayStack As String, ByVal needle As String) As Integer

Return (Len(hayStack) - Len(Replace(hayStack, needle, ""))) / Len(needle)
End Function

Private Function countOccurance3(ByVal hayStack As String, ByVal needle As String) As Integer

Dim i As Long, sHayStack As String : sHayStack = hayStack
Do Until InStr(sHayStack, needle) = 0
sHayStack = Replace(sHayStack, needle, "", 1, 1) : i += 1
Loop
Return i

End Function

I've not tested which is more effiecient, but all provides the similar results for many number tests.

Open XML Format SDK 2.0

Open XML documents provides strongly typed part and content classes for use

Open XML is an open ECMA 376 standard and is also approved as the ISO/IEC 29500 standard that defines a set of XML schemas for representing spreadsheets, charts, presentations, and word processing documents. Microsoft Office Word 2007, Excel 2007, and PowerPoint 2007 all use Open XML as the default file format.

The Open XML file formats are useful for developers because they use an open standard and are based on well-known technologies: ZIP and XML.

The Open XML Format SDK 2.0 is built on top of the System.IO.Packaging API and provides strongly typed part classes to manipulate Open XML documents. The SDK also uses the .NET Framework Language-Integrated Query (LINQ) technology to provide strongly typed object access to the XML content inside the parts of Open XML documents.

• Requirements:
  
  Supported Operating Systems: Windows Server 2003; Windows Vista; Windows XP Service Pack 2

This download requires the following:

• The Microsoft .NET Framework version 3.5.
• Up to 120 MB of available disk space.

“Be aware that it’s a 90MB download (about 120MB installed). About 100MB of it is documentation. The library itself (DocumentFormat.OpenXml.dll) is 3.5MB” as specified in windowsclientdevelopment.

The Open XML Format SDK 2.0 went live on April 7, 2009, and is now up for grabs via the Microsoft Download Center. The SDK, and the underlying System.IO.Packaging API enables developers to leverage a simplified manipulation process involving OpenXML packages. And when it comes down to manipulation of OpenXML packages, version 2.0 of the SDK brings to the table support for strongly typed part and content classes.

“In version 1 of the Open XML SDK we released the Open XML Packaging API, which allows you to create, open and manipulate Open XML files at the package and part level. In the first CTP of version 2 we released the Open XML Low Level DOM and Stream Reading/Writing components, which allow you to create and manipulate objects within xml parts contained in an Open XML package. In the second CTP of version 2 we are providing schema level validation functionality,” revealed Brian Jones, Office program manager.

In addition, the April 2009 CTP of Open XML Format SDK 2.0 permits OpenXML documents to be validated. The validation functionality added to the latest version of the SDK is designed to permit developers to perform validation of Open XML docs in relation to variations of the Open XML Format. Essentially what validation support is designed to do is to help reduce the possibility of invalid or corrupt Open XML files.

“Manipulating Open XML Formats by using the Open XML Base layer makes it much easier for you to work on the Open XML files, but doing so does not guarantee the production of valid Open XML files. The new Schema Level Validation component provides a mechanism to help you discover Open XML errors within files and in your code. This component assists you in debugging and validating Open XML files based on the schemas,” Jones added.

This release includes a high-level DOM (document object model) for Open XML development, as well as several tools to streamline Open XML development:

* The OpenXmlDiff utility identifies differences in the markup in two Open XML documents.

* The Open XML Class Explorer helps you determine which strongly typed class to use for a specific task, and includes the text of the relevant section of the ECMA-376 spec for each class.

* The Open XML Document Reflector takes a target document as input, and with a few clicks it shows you the C# code needed to generate that document (or a section of it) with the Open XML SDK.

Sample code that supports the scenarios described in the series of articles titled Creating Documents by Using the Open XML Format SDK 2.0 (Community Technology Preview)

The first article is located at:
http://msdn.microsoft.com/en-us/library/dd440953.aspx

Some brief overview can be seen from the link

Filling the DataGridView with all the files(upto deepest level) in specified directory

In case we need to fill a DataGridView in our form with all the files in the specified directory, no matter how deep many files exists, all the files are retireved from the directory and the related information is displayed in the DataGridView.

The steps to get the result as below:

1. Get the collection of FileInfo for each file in the directory/drive by using function explained in "Retrieve All Files Info in the specified Folder (Using LINQ To Object)" blog

2. Add the DataGridView component in the form name it anything say DataGridView1

3. Add the following string in the action corresponding to which data grid is needed to be filled with the file information:

       Dim arrList as New ArrayList

       getCompleteFileList1(directoryName, arrList)

       dataGridView1.DataSource= arrList

Or If only specific list of attributes for each file is needed to be displayed the the following lines can be considered:

       Dim arrList As New ArrayList

       getCompleteFileList1(directoryName, arrList)

        Dim filesInfo = From file As IO.FileInfo In arrList _

                       Select file.Name, file.DirectoryName, file.Length, file.LastWriteTime

        dataGridView1.DataSource = filesInfo.ToList

Retrieve All Files Info in the specified Folder (Using LINQ To Object)

        Public Sub getCompleteFileList1(ByVal rootDir As String, ByRef arrFileList As ArrayList) 

            If My.Computer.FileSystem.GetDirectoryInfo(rootDir).Name = "System Volume Information" Then

                Return

            End If

            For Each recursiveDir As String In My.Computer.FileSystem.GetDirectories(rootDir)

                Call getCompleteFileList1(recursiveDir, arrFileList)

            Next

            Dim files = From file In My.Computer.FileSystem.GetFiles(rootDir, FileIO.SearchOption.SearchTopLevelOnly) _

                        Order By file _

                        Select My.Computer.FileSystem.GetFileInfo(file)

            arrFileList.AddRange(files.ToList)

        End Sub

This function return a collection of System.IO.FileInfo objects that can be used to retrieve all files and their corresponding information with same list that can be used depending on the requirement.

If  only the specific attribute is desired for each file, then we can specify the needed attribute under the Select Key

Retrieve All Files in the specified Folder

Private Sub getCompleteFileList(ByVal rootDir As String, ByRef arrFileList As ArrayList)

If My.Computer.FileSystem.GetDirectoryInfo(rootDir).Name = "System Volume Information" Then

Return

End If

For Each recursiveDir As String In My.Computer.FileSystem.GetDirectories(rootDir)

Call getCompleteFileList(recursiveDir, arrFileList)

Next

For Each foundFile As String In My.Computer.FileSystem.GetFiles(rootDir,FileIO.SearchOption_
.SearchTopLevelOnly)

arrFileList.Add(foundFile)

Next

End Sub

rootDir can be root drive or some specific directory. arrFileList is the final list of files in rootDir' all subDir,Sub-SubDir,Sub-Sub-SubDir................ means all the existing files, no matter how much deeper, are added in th earrFileList that can be used for any needed purpose requiring all the list of files in some dir.

XML Operations: Create XML, Insert Data, Modify Data and Delete Data in XML File

• • Create XML File
    

  Private Sub CreateXmlFile()

          Dim xw As New XmlTextWriter("C:\mySampleXml.xml", System.Text.Encoding.UTF8)

          xw.WriteStartDocument()

          xw.WriteStartElement("nodes", "")

  
  

          xw.WriteStartElement("node", "")

          xw.WriteStartAttribute("id", "")

          xw.WriteString("1")

          xw.WriteEndAttribute()

          xw.WriteStartElement("child")

          xw.WriteString("sample10")

          xw.WriteEndElement()

          xw.WriteStartElement("child")

          xw.WriteString("sample11")

          xw.WriteEndElement()

          xw.WriteEndElement()

  
  

  
  

          xw.WriteStartElement("node", "")

          xw.WriteStartAttribute("id", "")

          xw.WriteString("2")

          xw.WriteEndAttribute()

          xw.WriteStartElement("child")

          xw.WriteString("sample20")

          xw.WriteEndElement()

          xw.WriteStartElement("child")

          xw.WriteString("sample21")

          xw.WriteEndElement()

          xw.WriteEndElement()

  
  

          xw.WriteStartElement("node", "")

          xw.WriteStartAttribute("id", "")

          xw.WriteString("3")

          xw.WriteEndAttribute()

          xw.WriteStartElement("child")

          xw.WriteString("sample30")

          xw.WriteEndElement()

          xw.WriteStartElement("child")

          xw.WriteString("sample31")

          xw.WriteEndElement()

          xw.WriteEndElement()

  
  

          xw.WriteEndElement()

          xw.Flush()

          xw.Close()

          Process.Start("C:\mySampleXml.xml")

      End Sub

  
  

  
  

  • Insert Data in XML File
    

  Private Sub InsertDataToXmlFile()

          Dim xDoc As New XmlDocument

          xDoc.Load("C:\mySampleXml.xml")

          Dim sourceRootNode As XmlNode = xDoc.SelectSingleNode("/nodes/node[@id=2]") 'Slects the root 'nodes'

          Dim newChildNode As XmlNode = xDoc.CreateNode(XmlNodeType.Element, "child", "")

          newChildNode.InnerText = "New Sample 22"

  
  

          'Child with attribute

          Dim newChildNode1 As XmlNode = xDoc.CreateNode(XmlNodeType.Element, "child", "")

          Dim atr As XmlAttribute = xDoc.CreateAttribute("childID")

          atr.Value = "ch1"

          newChildNode1.InnerText = "New Sample 23"

          newChildNode1.Attributes.Append(atr)

          sourceRootNode.AppendChild(newChildNode)

          sourceRootNode.AppendChild(newChildNode1)

          xDoc.Save("C:\mySampleXml.xml")

          Process.Start("C:\mySampleXml.xml")

  
  

      End Sub

  
  

  
  

  • Modify Data in XML File
    

      Private Sub ModifyDataInXmlFile()

          Dim xDoc As New XmlDocument

          xDoc.Load("C:\mySampleXml.xml")

          Dim desiredNode As XmlNode = xDoc.SelectSingleNode("/nodes/node[@id=2]")

          Dim childNodes As XmlNodeList = desiredNode.SelectNodes("./child") ''.' specifies the current node and '/child' specifies child nodes

          For Each curNode As XmlNode In childNodes

              If curNode.HasChildNodes = True Then

                  If curNode.Attributes.Count > 0 Then

                      If curNode.Attributes("childID").Value = "ch1" Then

                          curNode.InnerText = "Updated Sample 23"

                      End If

                  End If

              End If

          Next

          xDoc.Save("C:\mySampleXml.xml")

          Process.Start("C:\mySampleXml.xml")

  
  

      End Sub

  
  

  
  

  • Delete Data in XML File
    

      Private Sub RemoveDataFromXmlFile()

          Dim xDoc As New XmlDocument

          xDoc.Load("C:\mySampleXml.xml")

          Dim desiredNode As XmlNode = xDoc.SelectSingleNode("/nodes/node[@id=2]")

          Dim childNodes As XmlNodeList = desiredNode.SelectNodes("./child") ''.' specifies the current node and '/child' specifies child nodes

          For Each curNode As XmlNode In childNodes

              If curNode.HasChildNodes = True Then

                  If curNode.Attributes.Count > 0 Then

                      If curNode.Attributes("childID").Value = "ch1" Then

                          curNode.ParentNode.RemoveChild(curNode)

                      End If

                  End If

              End If

          Next

          Dim anotherDesiredNode As XmlNode = xDoc.SelectSingleNode("/nodes/node[@id=2]")

          anotherDesiredNode.ParentNode.RemoveChild(anotherDesiredNode)

          xDoc.Save("C:\mySampleXml.xml")

          Process.Start("C:\mySampleXml.xml")

  
  

      End Sub

  
  

  Please give any suggestions for better coding. Also add code for other possible cases that can be  possible for other various situations.

  
  

Convert Bitmap picture to Byte() and back to picture

[Not tested Code]

Let pic be the picture as
Dim pic as Bitmap

and Let bytes() be the required converted picture into byte.
Dim bytes() As Byte

Then the code to convert the picture to bytes as below:

If picture IsNot Nothing Then
Dim BitmapConverter As System.ComponentModel.TypeConverter = System.ComponentModel.TypeDescriptor.GetConverter(picture.[GetType]())
bytes= DirectCast(BitmapConverter.ConvertTo(picture, GetType(Byte())), Byte())
Else
bytes= Nothing
End If

Also to get picture back to bitmap format from the byte object the code will be like as below:

If bytes IsNot Nothing Then
pic= New Bitmap(New MemoryStream(value))
Else
pic = Nothing
End If

Uses:
The picture can't save directly in XML file and is required to be converted to like bytes only then can be saved to XML file. Similarly later it can be retrieved back to picute in bitmap format by using the above procedure.

SendKys

In an application sometimes we may face to send a key to the application or environment after some event occures. VB.Net provides a way to send keys to window forms by using

System.Windows.Forms.SendKeys.Send("your key comes here")

there are various codes for various keys. The list of syntax of all the keys is given below:


Key Code
BACKSPACE {BACKSPACE}, {BS}, or {BKSP}
BREAK {BREAK}
CAPS LOCK {CAPSLOCK}
DEL or DELETE {DELETE} or {DEL}
DOWN ARROW {DOWN}
END {END}
ENTER {ENTER}or ~
ESC {ESC}
HELP {HELP}
HOME {HOME}
INS or INSERT {INSERT} or {INS}
LEFT ARROW {LEFT}
NUM LOCK {NUMLOCK}
PAGE DOWN {PGDN}
PAGE UP {PGUP}
PRINT SCREEN {PRTSC}
RIGHT ARROW {RIGHT}
SCROLL LOCK {SCROLLLOCK}
TAB {TAB}
UP ARROW {UP}
F1 {F1}
F2 {F2}
F3 {F3}
F4 {F4}
F5 {F5}
F6 {F6}
F7 {F7}
F8 {F8}
F9 {F9}
F10 {F10}
F11 {F11}
F12 {F12}
F13 {F13}
F14 {F14}
F15 {F15}
F16 {F16}

To specify keys combined with any combination of the SHIFT, CTRL, and ALT keys, precede the key code with one or more of the following codes:

Key Code
SHIFT +
CTRL ^
ALT %

Getting String object as Stream IO.Stream object

let myString be the String object that is needed to be converted into

Dim msObj As MemoryStream = New MemoryStream(System.Text.Encoding.ASCII.GetBytes(myString))

MyObjThatNeedsStreamObj.Load(CType(msObj , Stream))

Opening a Form by Type or Name

Opening a Form by Type or Name
You have a class that is able to trap an event, say the doubleclick of a textbox, and has to open a form when it occurs. If it's always the same form, that's easy, but what if you want it to be determined during runtime? This is a quite common story: doubleclick on article opens the detail form of that article, doubleclick on supllier opens that particular form. If you use a form variable, how do you say to the class which form should be opened? This will not work

Code:

Dim FormToOpen as Form 'you don't want to open it right away, you want to know when the time comes what form to open
FormToOpen = Form1

You could say FormToOpen = new Form1, but then 1. an instance would be immediately created, even if it never will be used: memory leak. 2. you can never close the form, you'll always have to use the same instance created when setting the form. Consequently, you can never open more than 1 instance using this way.

The solution: use the type. If you know the type, the Activator class will enable you to open (and return) an instance of that form at any time and as much times as you like. (The Activotor class exposes the function CreateInstance which returns an instance of the specified object)
The following code creates an instance of the type form1 and shows it.

Code:

CType(Activator.CreateInstance(GetType(Form1)), Form).Show()
. . . . . . . .. . . . . . . .. . . . . . . .

WMI Scripting

WMI (Windows Management Instrumentation) - Home

Introduction to WMI

Who will benefit from learning about WMI (Windows Management Instrumentation) commands? Here are the people who I had in mind as I wrote this section. Network managers who want to collect specific data from one (or more) server. IT professionals who what to know precisely what's happening in their Microsoft operating system. Those techies who love remote control without hassle. . . . . . . . . . . . . . . . . . . . . . . . . . .

------------------------------------------------

WMI Scripting can be used to retrieve many useful information related to running machine in a very easy way.

Tutorial Learning Points

1) Sometimes simple phrases have a beauty all of their own. Yet, often simple phrases hide all the hard work, what you do not see is all the experiments that did not work and all the extra code that you don't need. Perhaps the best way to re-enforce this theme is to point what NOT to put in the WQL clause.

2) ("Select * from Win32_LogicalDisk where objItem.FreeSpace > 10000"). No need for objItem, just the pure property name. As with all scripting learn to apply the punctuation correctly.

Example 2 - Select only File Systems that are NTFS.

The key WQL clause is where FileSystem = 'NTFS'")

("Select * from Win32_LogicalDisk where FileSystem = 'NTFS'")

Tutorial Learning Points

1) In truth, text filters are harder than numeric filters. The greatest problems are with the speech marks.

("Select * from Win32_LogicalDisk where FileSystem = 'NTFS'"). Again looks easy, but here are some mistakes. Where FileSystem = ' NTFS '". It is outrageous that blank spaces should cause problems - but they do.

2) Here is another error, note the wrong type of speech marks. where FileSystem = "NTFS"". The spacing is correct but NTFS should be bracketed by a pair of single speech marks, the double quotes draws an error message.

. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .. . . . . .

Saving all the images from ImageList to Disk

Public Sub saveImageListToDisk()
Dim img As Image
Dim iCnt As Integer
For Each img In ImagList1.Images
iCnt = iCnt + 1
img.Save("C:\MyImages\" & iCnt & ".png")
Next
End Sub