Freeze Table Header and Columns

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Introduction

I was developing a web based application that needed a datagrid/table that can freeze its header and columns, and also have a complex that consists of merged cells. I have searched on the internet but I still can't find the one that I wanted. So, I decided to build it by my self, and thank god I made it :). And now I want to share the code with the world. This article describe how to build a table with freeze capability using built-in ASP.Net controls and some HTML tags.

Using the code

To build the freeze-able table we need to use the DIV, TABLE tag, ASP.Net Panel and PlaceHolder control and of course some javascript and CSS. You can see the layout in Figure 1.

Figure 1. The layout to position the tag and controls.

Object Name	Description
divScrollbar	We will use this to show horizontal scrollbar. So we can show the hidden area of tblPart2 using JavaScript and give the impression that we freeze the columns in tblPart1. This will be accomplished using JavaScript.
ASP Panel control	Optional. This will be used only if you want to be able to show or hide the entire objects.
divItems	This DIV will be used for vertical scrollbar so we can give impression to the user that the header is frozen. We will do this using CSS.
TABLE tag	To synchronize the position of tblPart1 and tblPart2.
tblPart1	This table will be container of the freezing columns. We will generate the rows later.
divPart2	This DIV is use to clip the view of tblPart2
tblPart2	This table is like tblPart1, but some of it's columns is hidden by divPart2. This table will be scrolled horizontally by divScroller. The header and rows will be generated later.
PlaceHolder1	Act as the container for the generated rows for tblPart1.
PlaceHolder2	Act as the container for the generated header and rows for tblPart2.
Table 1. Functional description of the objects

To freeze the header we can use the following CSS code:

tr.head
{
 position:relative; top: expression(document.all["divItems"].scrollTop-1); 
}

Building the horizontal scrollbar

To mimic IE scrollbar we can place a DIV tag inside a DIV tag. And resize both of them at run-time using JavaScript, this is done in ResizeTables() function.

 function ResizeTables()
 {         
  if (document.readyState)
  {  
       
   if (!document.all['divItems']) return;
   divItems.style.width = document.body.clientWidth-17;
   divItems.style.left = 0;        
       
   divPart2.style.width = document.body.clientWidth-155; 
   scroll1.style.width = divItems.style.width;
   scroll1.style.width = divItems.style.width;
   if(screen.width > 800)
    spacing1.style.width = tblPart2.offsetWidth+ tblPart1.offsetWidth;
   else
    spacing1.style.width = tblPart2.offsetWidth+ tblPart1.offsetWidth;          
           
   var AvailableHeight;
   AvailableHeight = 500;                
   divItems.style.height  = AvailableHeight;           
      
   divPart2.style.width = divItems.offsetWidth - tblPart1.offsetWidth-2;  
   
   if (parseInt(divPart2.style.width) + 
      tblPart1.offsetWidth < document.body.clientWidth )
   {  
    if (screen.width > 800)
    {              
     if(parseInt(divItems.style.height) < divPart2.offsetHeight)
     {                                                   
      divPart2.style.width = divItems.offsetWidth  -tblPart1.offsetWidth-19;
     }
    }
    else
    {
     if(parseInt(divItems.style.height) > divPart2.offsetHeight)
     {                         
      divPart2.style.width = divItems.offsetWidth -tblPart1.offsetWidth-2;
     }            
     else
     {
      divPart2.style.width = divItems.offsetWidth -tblPart1.offsetWidth-19;
     }           
    }

   }
  }
 }
 
 function OnScroll(sc)
 {  
  document.getElementById("divPart2").scrollLeft = sc.scrollLeft; 
 }         
 window.onload = ResizeTables;
 window.onresize = ResizeTables;