Niranjan Kala's coding blog

on software development and productivity

Free Programming Books

There was thread on Stackoverflow which contribute the list of free programming books. The Original Source for these free books as below:
 List of freely available programming books
Further I found a nice maintained list on GitHub – Free programming books and subset of the list is here:

Parallel Programming
Partial Evaluation
Professional Development
Programming Paradigms
Regular Expressions
Reverse Engineering
Software Architecture
Theoretical Computer Science
Web Performance

Orchard CMS Learning stuff.

Recently I try to learn about the CMS which are developed in Microsoft technologies as there are lots of mature CMS available like joomla, Druple etc. These are based on the PHP and mostly hosted on apache(Linux based web server). Though I am working on .net stack so I decided to start with some open source CMS developed in technology and I decided to start learning with Orchard.

What is Orchard:
Orchard is a free, open source, community-focused Content Management System built on the ASP.NET MVC platform.

Orchard is built on a modern architecture that puts extensibility up-front, as its number one concern. All components in Orchard can be replaced or extended. Content is built from easily composable building blocks. Modules extend the system in a very decoupled fashion, where a commenting module for example can as easily apply to pages, blog posts, photos or products. A rich UI composition system completes the picture and ensures that you can get the exact presentation that you need for your content.

Here are few learning resources that I want to share with others also:

              How to resolve “The 'DesignerPackage' package did not load correctly” issue??

              It was the today morning I just start preparing to do my work and opened Visual Studio. Now what I found that there was lots popup showing the error for load fail of the designer packages respectively.

              The error  was “The 'DesignerPackage' package did not load correctly” and I did following trick to solve this issue in Visual studio 2013. If you are using older version then look for 11.0 or 10.0 folder for this “ComponentModelCache” directory.

              1. First open windows explorer and go to “C:\Users\<your users name>\AppData\Local\Microsoft\VisualStudio\12.0\ComponentModelCache”.

              2. Delete all the files located in this folder after closing the visual studio.

              After doing this start your visual studio and all errors went away.

              How to iterate through TileView items in XtraGrid?

              This is related to DevExpress question - How to loop through tiles in TileView, which help me to achieve the required functionality in the XtraGrid using the TileView. I require to implement the selection process for TileView similar to GridView in XtraGrid, but I require to iterate through all the TileView items. TileView actually use TileViewControl internally so it require to access under laying  tileview control items to access more information about the TileViewItems. See the below code snippet:

              private void HandleTileItemSelection(TileViewItem tileViewItem)
                  if ((ModifierKeys & Keys.Control) != Keys.Control)
                      Dictionary visibleTiles = ((tileView1.GetViewInfo() as ITileControl).ViewInfo as TileViewInfoCore).VisibleItems;
                      int alternateCheckedItemsCount = 0;
                      foreach (KeyValuePair item in visibleTiles)
                          if (item.Value != tileViewItem && item.Value.Checked)
                              item.Value.Checked = false;
                              tileView1.SetRowCellValue(item.Value.RowHandle, "CheckedStatus", false);

              RANDBETWEEN(m,n) in Sql Server?

              Today I have to find random number between two numbers lots of the time in the stored procedures So I tried to create a function which return random numbers between two boundary numbers m and n. I tried to look for the solution and got below logic to implement the function.

              Let m = 5 and n = 500 and method call would be RANDBETWEEN(5, 500). Then logic to find the random number would be as below:

              • Use RAND() (which returns a value between 0 and 1 (exclusive).
              • multiply by 298 (since you want a dynamic range of [300-3] = 297 + 1)
              • add 3 to Offset
              • and cast to INT?
              SELECT CAST(RAND() * 298 + 3 AS INT)
              A Stored Procedure can be written like this if it supposed to be reuse in code more often:
              @LowerBound int = 0 ,
              @UpperBound int = 1 , 
              @ret int OUT
                  SET NOCOUNT ON;
                  SELECT @ret = (CAST((RAND() * (@UpperBound - @LowerBound)) + @LowerBound AS INT));
              RETURN ;

              Call can be made like this:

              DECLARE @tmp INT;
              EXECUTE [dbo].[RANDBETWEEN] 0,10, @ret=@tmp OUT ;
              SELECT @tmp

              To create a function I found that I have to create a View that make random method call and then function will do remaining operation to get the random number.

              CREATE VIEW Get_RAND
              SELECT RAND() AS RANDNumber

              Then you can create a function like this (accessing the view with the SELECT RandomNumber... ) :
              CREATE FUNCTION RANDBETWEEN(@LowerBound INT, @UpperBound INT)
              RETURNS INT
                  DECLARE @TMP FLOAT;
                  SELECT @TMP = (SELECT RandomNumber FROM Get_RAND);
                  RETURN CAST(@TMP* (@UpperBound - @LowerBound) + @LowerBound AS INT);

              Then this function can be called as below:

              SELECT [dbo].[RANDBETWEEN](1,10)

              WCF or ASP.NET Web APIs for web services??

              This is a interesting question for everyone and especially for me too. Whenever I got chance to dig for these technologies to create service, I found myself little confuse that which one should I choose.

              It may be the “WCF vs ASP.NET Web API” contest for choosing in particular scenario and requirement of client. I got lots of reference and comparison related these two things which are discussed below:

              The ASP.NET Web API is a continuation of the previous WCF Web API project (Conceptual changes are described on Codeplex WCF documentation - How to Migrate from WCF Web API to ASP.NET Web API).

              Here is comparison from MSDN - WCF and ASP.NET Web API:

     Web API is all about HTTP and REST based GET,POST,PUT,DELETE with well know MVC style of programming and JSON returnable; web API is for all the light weight process and pure HTTP based components. For one to go ahead with WCF even for simple or simplest single web service it will bring all the extra baggage. For light weight simple service for ajax or dynamic calls always WebApi just solves the need. This neatly complements or helps in parallel to the MVC.

              WCF was originally created to enable SOAP-based services. For simpler RESTful or RPCish services (think clients like jQuery) ASP.NET Web API should be good choice.

              In the scenarios listed below you should go for WCF:

              1. If you need to send data on protocols like TCP, MSMQ or MIME
              2. If the consuming client just knows how to consume SOAP messages

              We can expose REST endpoints on WCF services as well.

              WEB API is a framework for developing RESTful/HTTP services.

              There are so many clients that do not understand SOAP like Browsers, HTML5, in those cases WEB APIs are a good choice.Although WCF provides some support for writing REST-style services, the support for REST in ASP.NET Web API is more complete and all future REST feature improvements will be made in ASP.NET Web API.

              Here are few nice articles and reference:
              WCF or ASP.NET Web APIs? My two cents on the subject
              Scott Hanselman’s - Podcast 264 - This is not your father's WCF - All about the WebAPI with Glenn Block

              What is the correct way to handle exceptions and UnobservedTaskException in the TPL?

              Information from: A Task's exception(s) were not observed either by Waiting on the Task or accessing its Exception property. As a result, the unobserved exception was

              If you create a Task, and you don't ever call task.Wait() or try to retrieve the result of a Task<T>, when the task is collected by the garbage collector, it will tear down your application during finalization. For details, see MSDN's page on Exception Handling in the TPL.

              The best option here is to "handle" the exception. This can be done via a continuation - you can attach a continuation to the task, and log/swallow/etc the exception that occurs. This provides a clean way to log task exceptions, and can be written as a simple extension method, ie:

              public static void LogExceptions(this Task task)
                  task.ContinueWith( t =>
                       var aggException = t.Exception.Flatten();
                       foreach(var exception in aggException.InnerExceptions)
              With the above, you can prevent any task from tearing down the app, and logging it, via:
              Task.Factory.StartNew( () => 
                     // Do your work...
              Alternatively, you can subscribe to the TaskScheduler.UnobservedTaskException and handle it there. 

              Continuation of the task could determine the status of the parent task whether it get faulted or completed to success. A continuation can find out if an exception was thrown by the antecedent Task by the antecedent task's exception property. The following code snippet will print the results of a NullReferenceException to the console.

              Task task1 = Task.Factory.StartNew (() => { throw null; });
              Task task2 = task1.ContinueWith (ant => Console.Write(ant.Exception());
              If task1 throws an exception and this exception is not captured/queried by the continuation then it is considered unhandled and the application get halted. With continuations it is enough to establish the result of the task via the Status property.
              asyncTask.ContinueWith(task =>
                  // Check task status.
                  switch (task.Status)
                      // Handle any exceptions to prevent UnobservedTaskException.             
                      case TaskStatus.RanToCompletion:
                          if (asyncTask.Result)
                              // Do stuff...
                      case TaskStatus.Faulted:
                          if (task.Exception != null)
                              mainForm.progressRightLabelText = task.Exception.InnerException.Message;
                              mainForm.progressRightLabelText = "Operation failed!";
              If you don't use continuations you either have to wait on the task in a try/catch block or query a task's Result in a try/catch block. See below code snippet:
              int x = 0;
              Task task = Task.Factory.StartNew (() => 7 / x);
                  // OR.
                  int result = task.Result;
              catch (AggregateException aggEx)

              How to close a MessageBox after several seconds?

              Related to: Close a MessageBox after several seconds.
              I need to create a message box or Popup which must be visible for specified time and close automatically after then.

              There is not inbuilt feature in .net framework to do this. You need to create your custom logic that message box close after a specific time. To do this create a custom message box class which have a timer which close the raised pop message when elapsed time equal to specified time to make it visible to the user.
              Here is the custom class:

              public class AutoClosingMessageBox {
                  System.Threading.Timer _timeoutTimer;
                  string _caption;
                  AutoClosingMessageBox(string text, string caption, int timeout) {
                      _caption = caption;
                      _timeoutTimer = new System.Threading.Timer(OnTimerElapsed,
                          null, timeout, System.Threading.Timeout.Infinite);
                      MessageBox.Show(text, caption);
                  public static void Show(string text, string caption, int timeout) {
                      new AutoClosingMessageBox(text, caption, timeout);
                  void OnTimerElapsed(object state) {
                      IntPtr mbWnd = FindWindow(null, _caption);
                      if(mbWnd != IntPtr.Zero)
                          SendMessage(mbWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
                  const int WM_CLOSE = 0x0010;
                  [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
                  static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
                  [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
                  static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

              It can be called as below:

              AutoClosingMessageBox.Show("Text", "Caption", 1000);

              How to prevent selection change in drop down from key press when UltraComboEditor’s DropdownStyle set to DropDownList?

              Current requirement is that user can select option from drop down from mouse selection only, but whenever use type anything in the drop down it automatically raise control’s ComboBox.SelectionChangeCommitted event with first match that satisfies auto complete condition of the control. As required we need
              ignore the key press to raise the ComboBox.SelectionChangeCommitted event of the combo box and it only allow selection only on mouse.



              To do this, I set the control’s DropdownStyle set to DropDownList, but no work correctly. Along this I have to suppress combo box’s key press by handling KeyDown event as below.

              LibraryListDropdown libDropdown = null;
              public Form1()
                  libDropdown = new LibraryListDropdown();
                  this.libDropdown.DropDownStyle = DropDownStyle.DropDownList;
                  libDropdown.Name = "cmbObjectType";
                  libDropdown.SelectionChangeCommitted += new EventHandler(libDropdown_SelectionChangeCommitted);
                  libDropdown.KeyDown += libDropdown_KeyDown;
              void libDropdown_KeyDown(object sender, KeyEventArgs e)
                  e.SuppressKeyPress = true;
              private void libDropdown_SelectionChangeCommitted(object sender, EventArgs e)

              How to display tooltip on mouse hover in particular cell or column cell?


              Today I got an assignment to display tooltip on particular column cell depending on its text that contain some specific prefix to create different tool tip text.  The grid control was used is Infragistics UltraWinGrid to populate data to user.


              Most of the time I work with DevExpress controls and default win form controls, there we have different approach to get the grid element when hovering mouse over the grid element.  These controls use HitTestInfo to determine that which grid element currently hovered. While looking for the solution I found one Stackoverflow thread - DataGridView.HitTestInfo equivalent in Infragistics UltraWinGrid? . I am also hunting for the same question’s answer that does Infragistics’s UltraGrid control provides functionality similar to that of DataGridView.HitTestInfo?

              Source - Task-based Tutorial - How to use ToolTips with the Infragistics UltraWinGrid

               I found out that Infragistics controls don't convert the coordinates, but they use a special Infragistics grid event (MouseEnterElement) to get the element, which the mouse currently hovers over. Also with the Infragistics UltraWinGrid-control it required to keep track of the grid-row, over which the cursor is hovering. In contrast to our generic solution, the position is stored in a data-type provided by the UltraWinGrid-control and not in a Point-structure: 

              Public Class Form1
                  Inherits System.Windows.Forms.Form 
                  'Holds the row/column-coordinates of the cell on which
                  'the mouse is hovering...
                  Private mCurrentCell As Infragistics.Win _ 
                              .UltraWinGrid.UltraGridCell = Nothing

              The way of implement for the generic grid-control (in the section on "How to use ToolTips with grid-controls"), the whole logic, to keep track of the current mouse-position in terms of grid-coordinates (row/column) and to provide the tooltip with the content of the current grid-element, is located in the MouseEnterMouseLeave and MouseMove event-handlers. This is slightly different for the UltraWinGrid-control. Of course, the needed logic is also coupled to mouse-events, but the UltraWinGrid-control provides additional mouse-related events, which make the integration even easier. 


              Code snippet to show tooltip while using UltraWinGrid:

              private void ultraGrid1_MouseEnterElement(object sender, UIElementEventArgs e)
                  if (e.Element is RowUIElement)
                      if (e.Element.SelectableItem is UltraGridRow)
                          UltraGridRow ultraGridRow = (UltraGridRow)e.Element.SelectableItem;
                          if (ultraGridRow.Band.Key == PaletteZoneHVACGroupingConstants.BAND_PARENT)
                              toolTip.ToolTipText = "Drag-n-drop here";
                  else if(e.Element is CellUIElement)
                      // Get a refernce to the column.
                      UltraGridColumn column = (UltraGridColumn)e.Element.GetContext();
                      if (column != null && column.Key == ColumnName.DESIGNTEMPLATE)
                          UltraGridCell cell = e.Element.SelectableItem as UltraGridCell;
                          if (cell.Row.Band.Key == Constants.BAND_PARENT)
                              string toolTipMessage = string.Empty;
                              if (cell.Text.StartsWith(Constants.TextDesginChangePrefix))
                                  toolTipMessage = ResourceMessage.GetMessage(ResourceConstants. DESGINS_CHANGE);
                              else if (cell.Text.StartsWith(Constants.TextParametersChangePrefix))
                                  toolTipMessage = ResourceMessage.GetMessage(ResourceConstants.DESGINS_PARAMETERS_CHANGE);
                              if (!string.IsNullOrWhiteSpace(toolTipMessage))
                                  toolTip.ToolTipText = toolTipMessage;
              private void ultraGrid1_MouseLeaveElement(object sender, UIElementEventArgs e)



              How to set UltraToolTipeInfo in perticular row in win ultra grid control.

              display tooltip on mouse hover in cell