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ASP.NET - Drag and Drop on a Webpage

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28 Dec 20041 min read 365.2K   12.4K   123   59
Drag and drop contained objects on a webpage.

Introduction

Many web applications are required to be complex yet intuitive to the user. One way to achieve this is to create objects or areas of the web page draggable and droppable. Unfortunately, ASP.NET server controls do not have the Drag events and DragEventArgs. Fortunately, there is a way to enable drag and drop functionalities within a web page. Now keep in mind, this is not like a Windows application where you can drag files from the user's PC to the application. The drag and drop is limited to the boundaries of the web page.

Using the code

  1. Create a web application within your solution.
  2. Create a web page.
  3. Add the provided JavaScript in the <HEAD> of your <HTML>.
  4. Add two textboxes and a button in the web form.
  5. Add the DrawContainers method to the code-behind of the web page.
  6. Ensure that the click event for the button calls the DrawContainers method.

or

  • Download the source code and run the sample application.

JavaScript

This is the JavaScript that enables the drag and drop to take place:

JavaScript
<!--------- Drag and Drop JavaScript ------------>

var TimerID = 0;
var oEl     = null;
var oTarget = null;
var beginDrag = false;
var tmpHTML = "";
  
function killTimer()
{
    if (TimerID != 0 )
    {
        clearTimeout(TimerID);
        TimerID = 0;
    }
}
       
function fnShowDragWindow() 
{
    var obj = document.all("DW");
    
    killTimer();
    
    if (oEl == null)  
    {
        return;
    }
    
    obj.style.top        = oEl.offsetTop;
    obj.style.left        = oEl.offsetLeft;
    obj.style.height    = oEl.offsetHeight - 3;
    obj.style.width        = oEl.offsetWidth - 3;
    obj.innerText        = oEl.SpecimenId;
    obj.style.display    = "block";
    obj.style.zIndex    = 999;
    
    window.document.attachEvent( "onmousemove"  , fnMove );
    window.document.attachEvent( "onscroll"  , fnMove );
    window.document.attachEvent( "onmousemove" , fnCheckState );
    window.document.attachEvent( "onmouseup"    , fnRelease );
    window.document.attachEvent( "onselectstart", fnSelect );
    //window.document.attachEvent("onmouseover",setTarget);
    
    beginDrag = true;
}

function setTarget(id)
{
    var src = document.getElementById(id);
    
    if (src == null) 
    {
        return;
    }
    
    if (src.target == 'true')
    {
        oTarget = src;
    }
    else
    {
        oTarget = null;    
    }
}

function BeginDrag(id)
{
    // Get the item to be dragged.
    oEl = document.getElementById(id);
    
    // Is there an item?
    if(oEl == null)
    {
        return;
    }
    
    tmpHTML = oEl.innerHTML;
    // Set the window timeout.
    TimerID = setTimeout(fnShowDragWindow, 1);
}            


function fnCheckState()
{
    if(event.button != 1)
    {
        fnRelease();
    }
}

function fnSelect()
{
    return false;
}


function fnMove()
{
    if (event.button != 1)
    {
        fnRelease();
        return;
    }
    
    var obj = document.all("DW");
    
    obj.style.top = 
      event.clientY - (obj.offsetHeight/2) + window.document.body.scrollTop;  
    obj.style.left = event.clientX  + window.document.body.scrollLeft;
    window.status = 'Top=' + obj.style.top + ' Left=' + obj.style.left;
    
    if (event.clientY > window.document.body.clientHeight - 10 )
    {
        window.scrollBy(0, 10);
    }
    else if (event.clientY < 10)
    {
        window.scrollBy(event.clientX, -10);
    }
    
}

function fnRelease()
{
    if (beginDrag == false) return;
                           
    window.document.detachEvent( "onmousemove" , fnMove );
    window.document.detachEvent( "onscroll" , fnMove );
    window.document.detachEvent( "onmousemove" , fnCheckState );
    window.document.detachEvent( "onmouseup" , fnRelease );
    window.document.detachEvent( "onselectstart", fnSelect );
    //window.document.detachEvent( "onmouseover", setTarget );
    
    var obj = document.all("DW");
    
    if (oTarget != null) 
    {    
        var targetHTML = oTarget.innerHTML;
        var targetSpecId = oTarget.SpecimenId;
        var sourceSpecId = oEl.SpecimenId;
        
        oEl.innerHTML = targetHTML;
        oEl.SpecimenId = targetSpecId;
        oTarget.SpecimenId = sourceSpecId;
        
        oTarget.innerHTML = tmpHTML;
        
        // Is the container empty?
        if(oTarget.innerHTML != "")
        {
            oTarget.style.backgroundColor="beige";
        }
        else
        {
            oTarget.style.backgroundColor = "turquoise";
        }
        
        if(oEl.innerHTML != "")
        {
            oEl.style.backgroundColor = "beige"
        }
        else
        {
            oEl.style.backgroundColor = "turquoise"
        }
    }
    
    killTimer();
    
    obj.style.display    = "none";
    oEl                    = null;
    oTarget                = null;
    beginDrag            = false;
    TimerID                = 0;
}


function CancelDrag()
{
    if (beginDrag == false)
    {
        killTimer();
    }
}
<!--------- End of Drag and Drop JavaScript ------------>

C# code behind - DrawContainers method

This is the code behind used to create the drag and drop objects:

C#
private void DrawContainers()
{
    TableRowCollection trCol = this.Table1.Rows;
    TableRow tr = null;
    
    // Should we continue?
    if(this.txtContX.Text == null || this.txtContY.Text == null)
        return;
    
    // Size of the row.
    int rowSize = Int32.Parse(this.txtContX.Text); 
    // Number of rows.
    int rowNumber = Int32.Parse(this.txtContY.Text);
    // Total number of containers.
    int numberOfContainers = rowSize * rowNumber;
    // Boolean value for empty table cells.
    bool isEmpty = false;
    
    // Loop through all of the containers.
    for(int i=0; i< numberOfContainers; i++)
    {
        // new row mod.
        int newRow =  i % rowSize;
        
        // Should we create a new row?
        if(tr == null || newRow == 0)
        {
            tr = new TableRow();
            trCol.Add(tr);
        }

        // Empty cell generator.
        if((i+1)%17==0)
        {
            isEmpty = true;
        }
        else
        {
            isEmpty = false;
        }

        // Set the cell collection.
        TableCellCollection tdc = tr.Cells;

        // Create a new table cell.
        TableCell td = new TableCell();
        td.ID = "cell_" + i.ToString();
        
        // Set the cell backcolor.
        td.BackColor = Color.Turquoise;
        // Set the cell's class.
        td.CssClass = "SpecimenLoc";

        td.Attributes.Add("SpecimenId", "");

        // Is the cell empty?
        if(!isEmpty)
        {
            td.Attributes.Add("SpecimenId", i.ToString());
            td.BackColor = Color.Beige;
            td.Text = i.ToString();
        }
        
        // Add javascript attributes to the cell.
        td.Attributes.Add("target", "true");
        td.Attributes.Add("onmousedown", "BeginDrag(this.id);");
        td.Attributes.Add("onmouseup", "CancelDrag();"); 
        td.Attributes.Add("onmouseover", 
                "setTarget(this.id);this.style.cursor='hand';");
        td.Attributes.Add("onmouseout", 
                                "this.style.cursor='default';");
        td.Width = Unit.Pixel(35);
        td.Height = Unit.Pixel(35);

        // Add the cell to the cell collection.
        tdc.Add(td);
    }
}

C# code behind - button click event

The click event of the button:

C#
private void btnDrawContainers_Click(object sender, System.EventArgs e)
{
    // Draw the containers.
    this.DrawContainers();
}

License

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Comments and Discussions

 
GeneralMy vote of 5 Pin
Manoj Kumar Choubey9-Feb-12 21:13
professionalManoj Kumar Choubey9-Feb-12 21:13 
QuestionExplaination Pin
sakshictr10-Jan-12 19:34
sakshictr10-Jan-12 19:34 
QuestionNeed some Suggestions. Pin
supriya_rani2012-Sep-11 23:37
supriya_rani2012-Sep-11 23:37 
GeneralMy vote of 1 Pin
Member 449609922-Jun-09 20:55
Member 449609922-Jun-09 20:55 
GeneralGood Article Pin
khanjee7730-Dec-08 17:30
khanjee7730-Dec-08 17:30 
GeneralMy vote of 2 Pin
guest37538-Dec-08 2:47
guest37538-Dec-08 2:47 
Generalhii kenny Young Pin
ctcalyx6-Aug-07 21:06
ctcalyx6-Aug-07 21:06 
GeneralRe: hii kenny Young Pin
Rockrebel7-Aug-08 1:42
Rockrebel7-Aug-08 1:42 
GeneralRe: hii kenny Young Pin
Kenneth Young7-Aug-08 2:26
Kenneth Young7-Aug-08 2:26 
QuestionHyperLinkBitmap Error Pin
diddy4332-Jul-07 6:39
diddy4332-Jul-07 6:39 
GeneralDoens't work with firefox Pin
carlintveld31-May-07 7:50
carlintveld31-May-07 7:50 
GeneralRe: Doens't work with firefox Pin
vytas z.16-Aug-07 2:33
vytas z.16-Aug-07 2:33 
GeneralRe: Doens't work with firefox Pin
bbol19-Nov-07 12:49
bbol19-Nov-07 12:49 
GeneralDoes n't Work with ASP.Net 2005 Pin
Hari Darshan26-Apr-07 1:17
Hari Darshan26-Apr-07 1:17 
QuestionHow to get updated row after drag? Pin
davihigh12-Sep-06 3:29
davihigh12-Sep-06 3:29 
AnswerRe: How to get updated row after drag? Pin
Kenneth Young12-Sep-06 7:15
Kenneth Young12-Sep-06 7:15 
QuestionCheckbox. Pin
py1rdj4-Sep-06 11:20
py1rdj4-Sep-06 11:20 
AnswerRe: Checkbox. Pin
Kenneth Young12-Sep-06 7:17
Kenneth Young12-Sep-06 7:17 
QuestionDrag n Drop from listbox to a datagrid Pin
Coder.864-Sep-06 4:11
Coder.864-Sep-06 4:11 
This seems to be a gr8 implementation.Thanks to the author.
I have a query.
I need to drag and drop items from listbox to datagrid.
If anybody has implemented please help me out in this.
I tried out but i cant put it in the grid.

Thanks
Kumar.
AnswerRe: Drag n Drop from listbox to a datagrid Pin
Kenneth Young12-Sep-06 7:21
Kenneth Young12-Sep-06 7:21 
GeneralDatagrid to Datagrid drag drop Pin
sandeepautade31-Aug-06 2:31
sandeepautade31-Aug-06 2:31 
GeneralRe: Datagrid to Datagrid drag drop Pin
Kenneth Young31-Aug-06 2:39
Kenneth Young31-Aug-06 2:39 
GeneralDRAG DROP Pin
Mon217-Aug-06 20:45
Mon217-Aug-06 20:45 
GeneralRe: DRAG DROP Pin
Kenneth Young31-Aug-06 2:37
Kenneth Young31-Aug-06 2:37 
Generalmicrosoft treeview [modified] Pin
Mohd Azidi13-Jul-06 14:37
Mohd Azidi13-Jul-06 14:37 

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