Library tutorials & articles

Building a Full-Featured Custom DataGrid Control

By Dimitrios Markatos, published on 19 Mar 2005
Page 8 of 9
  1. Introduction
  2. A Look Ahead
  3. Our Page Setup
  4. Control Outline
  5. Building Our Control
  6. Let's Cache
  7. Now We Compile...
  8. DataGrid Enhancements
  9. Conclusion

DataGrid Enhancements

The final section below is compiled from forum questions that were posted to me and that I answered on DNJ. I also include additional code to further enhance the Datagrid's functionality in this article.

The four added topics are:

  1. How to customize the Datagrid pager
  2. Adding a Custom Datagrid ItemTemplate
  3. Formatting Column Output in the DataGrid
  4. Adding an Incremental Count Column To DataGrid

How to customize the Datagrid pager


For example, to get your Datagrid pager to display paging like "<Prev 12 13 14 15 Next>", you'll need to replace the start and end paging ellipses "..." with < Prev and Next >. How's that done? By enumerating through the paging link button controls, determine the index position for the ellipses and then replacing them.

Here's how:

Here is the entire GridCreated method. Replace the original one found in the article, with the following:

private void GridCreated (Object sender, DataGridItemEventArgs e)
{

    //Declare the ItemType
    ListItemType elemType = e.Item.ItemType;
    if (elemType == ListItemType.Item || elemType == ListItemType.AlternatingItem)
    {
        //A DataGrid Item represents an item (row) in the DataGrid control
        //e.Item is the table row where the command is raised
        DataGridItem dgRow = (DataGridItem) e.Item;
        int rowCntIncr = dgRow.DataSetIndex + 1; //Gets the index number of the DataGridItem object from the bound data source
        //Get the start and end index count from DataGrid
        //declare as typed variables first then convert
        StartCnt = rowCntIncr-dgRow.ItemIndex;
        EndCnt = rowCntIncr;
    }
    else if (elemType == ListItemType.Pager)
    {
        TableCell Pager = (TableCell) e.Item.Controls[0];
        //Additional Pager Text
        TableCell dgPagerText = new TableCell();

        dgPagerText.Width = Unit.Percentage(25);
        dgPagerText.ID = "dgPagerText";
        dgPagerText.HorizontalAlign = HorizontalAlign.Left;
        Label InfoText = new Label();
        InfoText.ID = "InfoText";
        dgPagerText.Controls.Add(InfoText);
        //Add Table Cell to Pager
        e.Item.Controls.AddAt(0, dgPagerText);

        //Add custom Previous/Next paging section
        //Loop indexed by 2 through datagrid paging numbers controls jumping over the spaces
        for (int i = 0; i <= Pager.Controls.Count; i+=2)
        {
            object pgNumbers = Pager.Controls[i];
            int bCnt = PagerStyle.PageButtonCount;
            int endPagingIndex = Pager.Controls.Count-1;
            if (pgNumbers.GetType().Name == "DataGridLinkButton")
            {
                LinkButton lb = (LinkButton) pgNumbers;
                //Deal only with ellipses
                if (lb.Text == "...")
                {
                    //Find index position of paging ellipses
                    if (i == 0)
                    {
                        lb.Text = "< Prev";
                    }
                    else if (i == endPagingIndex)
                    {
                        lb.Text = "Next >";
                    }
                }
            }
        }//End Loop
    }
}



Formatting Column Output in the DataGrid

To begin, you'll first want to disable AutoGenerateColumns by setting it to false, by doing so set your query to "Select * From ..." etc. Next, the following code would go into the classes GetDataGrid() method, right before the DataSource = GridCachedData(); line.

The code below creates custom BoundColumns that permit formatting. In this example we formatted our SupplierID as currency just to show how it's done, as in your question:

//Programmatic Custom BoundColumns
BoundColumn SupplierID = new BoundColumn();
BoundColumn CompanyName = new BoundColumn();
BoundColumn ContactName = new BoundColumn();
BoundColumn Country = new BoundColumn();
SupplierID.HeaderText="No.";
SupplierID.DataField="SupplierID";
SupplierID.DataFormatString = "{0:c}";
CompanyName.HeaderText="CompanyName";
CompanyName.DataField="CompanyName";
ContactName.HeaderText="ContactName";
ContactName.DataField="ContactName";
Country.HeaderText="Country";
Country.DataField="Country";

//Clear the DataGrid first
Columns.Clear();
//Add them to our Datagrid
Columns.Add(SupplierID);
Columns.Add(CompanyName);
Columns.Add(ContactName);
Columns.Add(Country);

Adding a Custom Datagrid ItemTemplate

I'll also demonstrate a couple of ways to programmatically add a custom ItemTemplate to your datagrid.

Normally, to get an ItemTemplate with your Datagrid, you'd do something like this:

<asp:TemplateColumn>
    <HeaderTemplate>Country</HeaderTemplate>
    <ItemTemplate>
        <asp:Label Text='<%# DataBinder.Eval(Container.DataItem, "Country") %>'
runat="server"/>
    </ItemTemplate>
</asp:TemplateColumn>

To do the same thing in our custom Datagrid control is easy. Here now we'll modify the "Country" datafield column in this case, programmatically.

Setting up an ItemTemplate is easy, as shown before in our BoundColumn thread, like so:

TemplateColumn Temp = new TemplateColumn();

Next, you add whatever TemplateColumn class members you wish. In this case, we'll add a header text:

Temp.HeaderText= "Country";

and then add it to your datagrid as in our previous DG formatting thread, in any order:

Columns.Add (Temp);

Now this works fine, except you won't get any data. Here are two ways to get data.

Method one is a quick and easy. To get something from this you can load an external server control:

Temp.ItemTemplate = Page.LoadTemplate("control.ascx");

This of course could contain pretty much whatever, within reason of course. The other method in getting data into your custom ItemTemplate is by implementing ITemplate. The class to do this is:

public class custDGTemplate : ITemplate
{
    private string fieldname;
    public custDGTemplate (string itemcolumname)
    {
        fieldname = itemcolumname;
    }
    public void InstantiateIn (Control container)
    {
        LiteralControl lc = new LiteralControl();
        lc.DataBinding += new EventHandler(this.OnDataBinding);
        container.Controls.Add (lc);
    }
    public void OnDataBinding (object sender, EventArgs e)
    {
        LiteralControl lc = (LiteralControl) sender;
        DataGridItem container = (DataGridItem) lc.NamingContainer;
        lc.Text = ((DataRowView) container.DataItem) [fieldname].ToString();
    }
}

Add this class anywhere within the mycustDG.cs source code file. Next, add the line below to your other custom ItemTemplate's members and pass the database field name to the to your custDGTemplate class, like so:

Temp.ItemTemplate = new custDGTemplate ("Country");

Adding an Incremental Count Column To DataGrid

I've got a cool little code snippet that you can add to the Datagrid to give it an new column with an incremental count. This first newly added column will have the count, with row 1 being 1, row 2 being 2, and the count goes on.

It's the same principle laid out in my myCustDG.cs class file's GridCreated method. So to implement this, you'll need to do two things:

1) In accordance to the previous two forum threads I added on creating custom templates, follow those examples and programmatically add another BoundColumn to the DataGrid so it can accommodate the incremental counting, like so:

BoundColumn Count = new BoundColumn();

Then add the header text:

Count.HeaderText = "No.";

Then add it to the DataGrid with the rest, just like in the other forum threads:

Columns.Add(Count);

2) Since we're already getting a count of how many records are found in our GridCreated method by showing us in our results – Results No. x to x, and now that we have just created a new column, all we need to do is write this number value to that column, by adding the two lines below to the GridCreated method, within the ListItemType.Item / ListItemType.AlternatingItem conditional after EndCnt = rowCntIncr; and before the ListItemType.Pager check:

//Add new Literal Control to write our Incremental Count from rowCntIncr
LiteralControl numberIncr = new LiteralControl(rowCntIncr.ToString());
//Write out to the first column the value count
dgRow.Cells[0].Controls.Add (numberIncr);

That's it, a quick and easy way to get an incremental count for your DataGrid.

Comments

  1. Ashish Dwivedi
    09 Oct 2006 at 13:32
    Hi,
    I am building a ASP .NET composite control containing a datagrid during which I am 
    finding a problem while paging of the grid.

    The problem is for example if I am having three pages to be displayed in the 
    datagrid, I have set the paging mode to be numeric.Now I am going to have 
    1,2,3 for navigation. 
    All navigations are working perfectly but when I go back to page 1 after page 2 
    or 3, the PageIndexChanged event is not triggered and I happen to see only the 
    information of previous page (i.e page 2 or page 3).



    Thanks in Advance 
    Ashish

















  2. hells_1999
    02 Feb 2006 at 08:16

    I build my own custom datagrid control using the code from your site.


    I used this control as a reference in another aspx page at you have mentioned in your article.
    I have 400 total number of records and my page count is 5. I wrote a stored procedure which will fetch 10 records each time for custom paging.


    When I click on ellipse after 5 it shoud page 6 to 10 but they link to first set of pages. So when I click on 6 it takes me to page 1 and so on. I am unable to navigate to more than 5 pages....


    Please Let me know...

  3. Will Rocca
    22 Dec 2005 at 15:23

    Quote:
    [1]Posted by taxiturner on 3 May 2005 10:25 PM[/1]
    LiteralControl lc = (LiteralControl) sender;
    DataGridItem container = (DataGridItem) lc.NamingContainer;
    lc.Text = ((DataRowView) container.DataItem) [columnName].ToString();




    I believe that "container" is your problem.
    try:


    lc.Text = ((DataRowView)e.Item.DataItem)[columnName].ToString();



    Now, if someone could just tell me how to cast a DataGridItemCollection as a TableRowCollection so that I don't get this error, that would be helpful.

  4. Hemant Kaushal
    22 Nov 2005 at 11:21

    I have created a Custom control using your article but i am having problem in sorting and update
    as i use a class which implements itemplate interface  for this and create the function for update and
    sorting  in same class.when i click on them the changes are made in database and dataset but they does not display on page and display on second click as these function are called in last i.e the getdatagrid() method is not called after them hence no changes are viewed.Please help me to resolve this problem.Can i use ipostbackdatahandler.


    Thanks in Advance

  5. sneha123
    31 Oct 2005 at 06:32

    There will be some 20 questions and  for each question there will be  4 choices.what i want to do is to select multiple answers by clicking the checkbox. i m using asp.net,vb.net
    pls help me


    we have written the code using radio button for selecting single item.but we  want to replace it with checkbox to select multiple items. the code using radio button is given below .pls correct it with checkbox


    Imports System.Data
    Imports System.Data.SqlClient
    Imports ELearning.LAIDBC
    Public Class Test
      Inherits System.Web.UI.Page
      Public ds As New DataSet()
      Public ds1 As New DataSet()
      Public ds2 As New DataSet()
      Public Score, Answered As Integer
      Protected WithEvents txtNoOfqns As System.Web.UI.WebControls.TextBox

    Region " Web Form Designer Generated Code "



      'This call is required by the Web Form Designer.
      <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()


      End Sub


      Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
          'CODEGEN: This method call is required by the Web Form Designer
          'Do not modify it using the code editor.
          InitializeComponent()
      End Sub
      Protected WithEvents lblCourse As System.Web.UI.WebControls.Label
      Protected WithEvents lblCourseName As System.Web.UI.WebControls.Label
      Protected WithEvents lblNoOfQuestions As System.Web.UI.WebControls.Label
      Protected WithEvents lblDurationInMinutes As System.Web.UI.WebControls.Label
      Protected WithEvents txtduration As System.Web.UI.WebControls.TextBox
      Protected WithEvents lblTimeLeft As System.Web.UI.WebControls.Label
      Protected WithEvents lblAnswered As System.Web.UI.WebControls.Label
      Protected WithEvents txtanswered As System.Web.UI.WebControls.TextBox
      Protected WithEvents DataGrid1 As System.Web.UI.WebControls.DataGrid
      Protected WithEvents submitbtn As System.Web.UI.WebControls.Button
      Protected WithEvents lab2 As System.Web.UI.WebControls.Label
      Protected WithEvents Lab4 As System.Web.UI.WebControls.Label
      Protected WithEvents Label2 As System.Web.UI.WebControls.Label
      Protected WithEvents lab1 As System.Web.UI.WebControls.Label
      Protected WithEvents txtans As System.Web.UI.WebControls.TextBox


    End Region


      Private ConDB As New ELearning.LAIDBC()
      Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
          If Session("Log") = Nothing Then
              Response.Redirect("frmLogin.aspx")
          End If


          If Not IsPostBack Then


              Try
                  Session("Course") = Session("URL2")
                  Session("Id") = "reshm-001"
                  Session("CandId") = "00000001"
                  'Response.Write(Session("Id"))
                  'Response.End()
                  Session("TotScore") = Nothing
                  Dim count1, str11 As String
                  ds1 = New DataSet()
                  ConDB.OpenConnection()


                  ds1 = ConDB.ExecuteSPReturnDS("ELSExecuteQuery", "select count(fUserId) from tblScore where fUserId='" & (Session("CandId")) & "'  and  fcourseid='" & Session("Id") & "' ")
                  ConDB.CloseConnection()
                  count1 = ds1.Tables(0).Rows(0)(0)
                  str11 = "select count(f    UserId) from tblScore where fUserId='" & (Session("CandId")) & "'  and  fcourseid='" & Session("Id") & "'"
                  'Response.Write(str11)
                  'Response.End()
                  If count1 < 3 Then
                      ' Response.Write(str11 & "," & count1)
                      ds2 = New DataSet()
                      Dim count2 As Integer
                      ConDB.OpenConnection()
                      ds2 = ConDB.ExecuteSPReturnDS("ELS    ExecuteQuery", "select count(fUserId) from tblScore where fUserId='" & (Session("CandId")) & "' and fresult='P'")
                      count2 = ds2.Tables(0).Rows(0)(0)
                      Response.Write(count2)
                      ConDB.CloseConnection()
                      If count2 > 0 Then


                          Session("msg") = "You have already passed for the test"
                          Response.Redirect("frmChance.aspx")
                      Else
                          Dim qrstr As String
                          Dim NoOfQuestionsToDisplay As Integer
                          Dim Mstring As String
                          Dim TotalNoOfQuestions As Integer
                          courseidselect()
                          Try
                              NoOfQuestionsToDisplay = txtNoOfqns.Text
                              Session("NoOfQuestionsToDisplay ") = txtNoOfqns.Text
                              ds = New DataSet()
                              ConDB.OpenConnection()
                              ds = ConDB.ExecuteSPReturnDS("ELSExecuteQuery", "select  count(*)  from tblQuestion where f_CourseId='" & Session("Id") & "'")
                              ConDB.CloseConnection()
                              TotalNoOfQuestions = ds.Tables(0).Rows(0)(0)
                              Session("TotQns") = TotalNoOfQuestions
                          Catch ex As Exception
                              R

  6. Rujuta
    05 Sep 2005 at 09:32
    I am having a datagrid where i am binding all boundcolumns from dataset and along with it i am having 2 templates , one is label and another checkbox . these two controls are bound to datagrid using itemplate class (i.e. dynamically) . when i am attaching checkbox and allocating event checkedchanged , its not getting fired and also i am unable to get how many checkbox are clicked (if autopostback=false) . if autopostback is true then datagrid is not displayed but if i again bind datagrid with all bouncontrols usinf sessions then i get same old datagrid but all checkbox are false .

    I hope i am clear with my problem . please help me in getting event fired for checkbox and also getting count for number of check box clicked .

    Thanks in advance,
    Rujuta
  7. Dimitrios Markatos
    15 Jul 2005 at 16:25
    Hi,

    You can implement one way as found in my other article here on DF - Dynamic Column Sorting and Paging in ASP.NET or you can download the upgraded version of my custom datagrid control with drag and drop columns and sorting.

    -Jimmy Markatos
  8. lamchoonho
    14 Jul 2005 at 04:53

    how can i implement sorting for all the column in this sample?

  9. enigma55
    23 Jun 2005 at 22:19
    I'm having the same problem.  Please let me know if you find anything.
  10. Dimitrios Markatos
    13 Jun 2005 at 15:37

    Hi all,


    I just re-added the forum post containing the new version of my article code. I just thought it easier to repost it again, since I find people requesting this and since the topics become hidden after a while, it won't show up unless you select all topics.


    Anyway, here is the link:


    Custom DG Ctrl w/ Dual Paging, Drag&Drop/Sort DL code forum post


    -Jimmy Markatos

  11. Dimitrios Markatos
    06 Jun 2005 at 19:07

    Right, I misunderstood you, as I was referring to DataSet data and I simply specified if you explicitly disabled view state, as yes, of course, true is the default. Now if you utilize what else I've mentioned then you shouldn’t have any issues.


    Also, I don't know what you mean with 2 other grids that maintain state. Are they all the same with dynamic item templates and all? As I can’t see your code I don’t know what you may have overlooked or otherwise.


    Therefore, employ the Page_Init method to help with this, but ultimately whenever something doesn't hold state by normal means as you would’ve hope it would then make use of view state.


    Hope this helps.

  12. anabhra
    06 Jun 2005 at 17:04

    I read this article on msdn:
    http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwebuiwebcontrolsdatagridcolumncollectionclasstopic.asp


    It seems to say that derived coumns (from say itemtemplate) that are added at run time are not saved to view state.


    They suggest having all needed cols and set visible attribute of those not needed for display to be set to false.


    I do have the EnableViewState=true (I think that is the default) on the page and grid.  I have 2 other grids that do maintain the state...


    -anabhra

  13. Dimitrios Markatos
    06 Jun 2005 at 16:59

    Yes, becuase by default all data within a DataSet is typically persisted in ViewState. Have you explcitly disabled Page ViewState? I don't see how your dynamically sized columns would reset themselves.


    At any rate, try enabling the DataGrid's DataGrid.EnableViewState property to true to maintains its state across HTTP requests.


    Furthermore, you can ideally stored any values you require to be persistant by storing those values in Session State.


    This should take care of it.


    - Jimmy Markatos

  14. anabhra
    06 Jun 2005 at 16:06

    I have one more question:


    When using template columns dynamically, are they stored in the view state?
    It seems not but I would like to have them as I have editable text boxes in the template columns that user enters data in...


    Many thanks,
    anabhra

  15. Dimitrios Markatos
    02 Jun 2005 at 20:26
    You're welcome. Glad to help!
  16. anabhra
    02 Jun 2005 at 20:23
    thanks a lot.

    your suggestion will work.

    I just solved my problem by setting the header template and itemtemplate widths. I had the grid in a div and that is why I could not see the widths. Once I set the table layout of the grid to fixed, I saw the columns being sized.

    again, many thanks for your interest.
  17. Dimitrios Markatos
    02 Jun 2005 at 20:20
    Sure, just add your datagrid column modifications in the ItemCreated event handler.

    Ex. in Pixels:
    Code:
    'VB
    Private Sub GridCreated (ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles GridCreated
      e.Item.Cells(0).Width = New Unit (100, UnitType.Pixel)
      e.Item.Cells(1).Width = New Unit (75, UnitType.Pixel)
    End Sub

    //C#
    private void GridCreated (object sender, DataGridItemEventArgs e)
    {
      e.Item.Cells[0].Width = new Unit (100, UnitType.Pixel);
      e.Item.Cells[1].Width = new Unit (75, UnitType.Pixel);
    }
    Furthermore, you can accomodate other Unit structures such as Percentage.

    Ex. in Percentage:
    Code:
    'VB
    Private Sub GridCreated (ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles GridCreated
      e.Item.Cells(0).Width = New Unit (50, UnitType.Percentage)
      e.Item.Cells(1).Width = New Unit (25, UnitType.Percentage)
       End Sub

    //C#
    private void GridCreated (object sender, DataGridItemEventArgs e)
    {
      e.Item.Cells[0].Width = new Unit (50, UnitType.Percentage);
      e.Item.Cells[1].Width = new Unit (25, UnitType.Percentage);
    }

    Hope this helps.

    - Jimmy Markatos
  18. anabhra
    02 Jun 2005 at 18:12
    I am dynamically creating/adding template columns to my datagrid. (implementing ITemplate interface).

    However, I am unable to set the width of this dynamically added column.

    any ideas?

    Many thanks,
    anabhra
  19. Dimitrios Markatos
    17 May 2005 at 19:48

    Glad to help!

  20. stevemets
    16 May 2005 at 21:50

    Excellent!

  21. Dimitrios Markatos
    16 May 2005 at 21:10

    Sure. You'll notice in my article's datagrid enhancements section How to customize the Datagrid pager, I show one way of manipulating the pager to which CSS could easily be added.


    Furthermore, in the article's forum post  I offer an improved version of my custom datagrid control, where I have added onmouseover rowhighlighting which further demonstrates CSS enhancement.


    Essentially, in modifying any elements of the datagrid, you’ll need to work with the grid’s OnItemCreated or OnItemDataBound methods to include any grid manipulations.


    Example:


    Your stylesheet:


    Code:
    <style>
    .DGPager {font-family: garamond; font-size:16px;}
    .DGPager a:link {font-size:16px; color:#0000FF;}
    .DGPager a:visited {font-size:16px; color:#C0C0C0;}
    .DGPager a:hover {font-size:16px; color:#FF0000;}
    </style>
    Next, add the event handler to your datagrid to call the method


    Code:
    OnItemCreated="Item_Created"
    And in the OnItemCreated method or in my article's GridCreated method, you add the following code in your code-behind or in your main page which determines you want to deal with the datagrid’s pager. The same goes for the header:
    Code:
    if (elemType == ListItemType.Pager) {


       e.Item.Cells[0].Attributes.Add("class","DGPager");


    }
    and for you in VB:


    Code:
    If (e.Item.ItemType = ListItemType.Pager) Then


       e.Item.Cells(0).Attributes.Add("class","DGPager")


    End If
    That’s it.


    -Jimmy Markatos

  22. stevemets
    16 May 2005 at 19:21

    Thanks- this seems to be a different approach.  I haven't looked at it in detail, but am interested.  It's interesting that the DataGrid with Month Pager Tabs was based on an article Dino wrote in ASP.Net Pro, and he also wrote the other 2 on editing the header, which I got to work, and on freezing the header, which I could not get to work (all of his samples in ASP.Net Pro are in C#, and I am still using VB, so I'm forced to use a translator which doesn't alway work.  They have just changed their policy to include both C# and VB, which is the best way to learn either in my opinion).


    Thanks for the help.  Do you know of any examples where the Pager can be manipulated with CSS?  

  23. Dimitrios Markatos
    16 May 2005 at 18:57

    Thanks stevemets,


    What you need is a custom pager control to give you the ability to provide fixed paging. I believe what you're looking for can be found here - Creating a Pager Control for ASP.NET by Dino Esposito.


    Hope this helps!

  24. stevemets
    15 May 2005 at 01:44

    Your Datagrid is very useful.  I have built a custom DG with paging set for Months (Jan-Dec) which serves up the sales for the month selected in the Pager Tab.  I have also enabled both Header Editing and Freezing Header as you scroll.  What I have not been able to do is to allow the Pager control to freeze in a similar manner as you scroll- the goal being to have the Header and Pager Tabs always visible so you don't have to go back to the top to change selection or remember what the data is in which column.  In general, I have not been able to apply any formatting using CSS to the pager at all.  Any help would be appreciated.


    Thanks!

  25. Dimitrios Markatos
    13 May 2005 at 14:26
    Cool, thanks. Glad to see it's helped you out.
  26. Sean Crouch
    09 May 2005 at 22:01
    Will take another look.

    Many thanks for your reply.

    Sean.
  27. James Crowley
    09 May 2005 at 20:51
    In order for those events to fire, you have to re-create the same controls when the page is reloaded. The DataGrid does this by using it's ViewState to restore the data it was originally bound to, and hence recreating all the rows in the table. You'd therefore have to do a similar trick of storing the data in the ViewState, and rebinding to that if DataBind() isn't called.
  28. Sean Crouch
    09 May 2005 at 17:02
    I wrote my own custom datagrid a short time ago, and included code that automatically handled the pageindexchanged and itemdatabound events. The upshot was that I could not get the code to run unless I re-bound the control on every page load.

    Is this normal?
    Conventional datagrids do not require this. What could I have been doing wrong?
    What are the issues with auto handling events with custom controls?

    many thanks
    Sean.
  29. taxiturner
    03 May 2005 at 22:25

    Doing someting similar to the code in the posting for "Building a Full-Featured Custom DataGrid Control" using datagrids and having a duece of a time getting past one problem.  
    The error encountered is System.InvalidCastException: Specified cast is not valid. I'm using the same code as up above for setting up the databinding for an item template in a datagrid. If I use a control file I have no problems with binding the data (from my SQL Server database).  But for some reason I can't assign the databinding using a code behind file .  Here's the code, just like up above as far as I can tell.


    LiteralControl lc = (LiteralControl) sender;
    DataGridItem container = (DataGridItem) lc.NamingContainer;
    lc.Text = ((DataRowView) container.DataItem) [columnName].ToString();


    Again, I have no problems binding to my itemtemplate column using other methods, so I'm wrather sure it's not a data issue.  I have seen mention on MSDN of this type of problem possibly being related to control tree hierarchy being re-ordered at this address http://support.microsoft.com/default.aspx?scid=kb;en-us;Q327287 but I couldn't see how to fix it from what they gave as a solution.  Their solution, to save you the trip, is this:
    "Make sure that the control tree is re-created on postback in the same order that it was saved at the end of the previous request."  My depth of .net knowledge doesn't go that deep.
    Any ideas?


    Thanks.


    Stack trace is here.
    [InvalidCastException: Specified cast is not valid.]
      DataGridTemplate.OnDataBinding(Object sender, EventArgs e) +13
      System.Web.UI.Control.OnDataBinding(EventArgs e) +66
      System.Web.UI.Control.DataBind() +26
      System.Web.UI.Control.DataBind() +86
      System.Web.UI.Control.DataBind() +86
      System.Web.UI.WebControls.DataGrid.CreateItem(Int32 itemIndex, Int32 dataSourceIndex, ListItemType itemType, Boolean dataBind, Object dataItem, DataGridColumn[] columns, TableRowCollection rows, PagedDataSource pagedDataSource) +169
      System.Web.UI.WebControls.DataGrid.CreateControlHierarchy(Boolean useDataSource) +1411
      System.Web.UI.WebControls.BaseDataList.OnDataBinding(EventArgs e) +49
      System.Web.UI.WebControls.BaseDataList.DataBind() +23
      Rock.BudgetDataGrid.datagridSetup(DataGrid datagrid) +914
      ASP.CreateProfilePage4aspx.PageLoad(Object sender, EventArgs e) in \CreateProfilePage4.aspx:28
      System.Web.UI.Control.OnLoad(EventArgs e) +67
      System.Web.UI.Control.LoadRecursive() +35
      System.Web.UI.Page.ProcessRequestMain() +750

  30. Dimitrios Markatos
    28 Mar 2005 at 00:48

    Hi all,


       I’ve added a newly enhanced version of my Custom Datagrid that adds some cool features and functionality including drag & drop columns that was incorporated from the wonderful article Extend the ASP.NET Datagrid with Client-side Behaviors by Dino Esposito found in the January 2004 issue of MSDN Magazine.


    I merged the code and functionality into the class assembly instead of the two found in the article. So in turn, you now really end with an awesome fully featured custom Datagrid control!


       The features are:
       
       1) Custom Paging taken from my article - Custom ASP.NET DataGrid Paging With Exact Count , alongside the conventional Datagrid paging setup.


       2) Drag & Drop Columns and Sorting from Dino Esposito's article


       3) Adding Background Image to Datagrid Header


       4) OnMouseover Datagrid Row Highlighting


       The only difference from this and my original article and code from "Building a Full-Featured Custom Datagrid Control" aside from the aforementioned, is in the code-behind setup. In this case, the dll class contains the drag & drop code and the Datagrid class only. My code-behind page inherits this and contains all of the remaining code.
       
       Be also sure to check out this article here on developerfusion.com where I have listed four additional Datagrid enhancements that you could incorporate into this Datagrid.


    Download the code here -> http://members.aol.com/dmarko1/dnjcode/CustDGDualPagingDragDrop_Sort.zip


    And feel free to send me an email and tell me what you think -- dmarko1@aol.com


    -Jimmy Markatos

  31. Dimitrios Markatos
    21 Mar 2005 at 18:23
    Hey folks,

    Here's one quick and easy way to add a background image to your Datagrid header, to give it a more fuller look. The code to do this is:

    Code:
    if (elemType == ListItemType.Header ) {

    e.Item.Style["background-image"] = "url(yourimage.jpg)";

    }


    Simply add this to my article's "myCustDG.cs"  source file code in the "GridCreated" method found at the end, recompile the source code to get your "myCustDG.dll"  and you're done.

    Even easier is my other forum post "Custom DG Control w/ Dual Paging, Drag & Drop/Sort" that has this incorporated into it and a whole lot more and you can download the code with all the enhancements here -> http://members.aol.com/dmarko1/dnjcode/CustDG_DualPaging_DragDrop_Sort.zip

    -Jimmy Markatos
  32. Developer Fusion Bot
    01 Jan 1999 at 00:00

    This thread is for discussions of Building a Full-Featured Custom DataGrid Control.

Leave a comment

Sign in or Join us (it's free).

Related tags

asp.net, datagrid
Dimitrios Markatos Dimitrios, or Jimmy as his friends call him, is a .NET developer/architect who specializes in Microsoft Technologies for creating high-performance and scalable data-driven enterprise Web and deskto...
AddThis

Related articles

Ask a question

Related discussion

Related podcasts

Events coming up

  • Jul 7

    DTC 70-528 Session 7: Chapter 12

    Greenwood Village, United States

    Due to lack of interest of the 5th Monday meetup, we will continue as originally scheduled. The topic of the night will be "Chapter 12 - Creating ASP.NET Mobile Web Applications", taught by RJ Hatch. It is a fairly small chapter, so we can discuss other topics as well. Pizza and beverages will be provided on a donation basis.

Languages

Web Development

Frameworks & Architecture

Other major sections

Cancel
Want to stay in touch with what's going on? Follow us on twitter!