Gridview Sorting and Paging with Dynamically Generated Controls

Question

I've gotten myself into a pickle with using dynamic controls in a gridivew.

I am binding the gridview to a list and am then adding dyanmic controls. IN order to keep the control state I need to do this in page load. However since events fire after page load I am unable to properly handle sorting and paging events. Are there any creative solutions to this problem or am I going about this all wrong?

EDIT: I am not sure I explained my problem correctly. It doesn't matter where I add the dynamic controls in the life cycle. The problem is that the sorting and paging events require me to rebind the GridView which (apparently) causes the properties assigned to my dynamic controls to be lost from ViewState since the binding on sorting and paging happens late in the life cycle.

protected void Page_Load(object sender, EventArgs e)
{       
   //NOTE: to maintain control state of dynamic controls all databinding needs to be done in page load. 
   grdProducts.DataSource = GetDataSource();
   grdProducts.DataBind();
}

protected void grdProducts_OnRowDatabound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType != DataControlRowType.DataRow) return;        

    ManufacturerProduct m = new ManufacturerProduct();

    m.Model = DataBinder.Eval(e.Row.DataItem, "Model").ToString();

    PlaceHolder ph = new PlaceHolder();        
    ph = (PlaceHolder)e.Row.FindControl("phAddToCart");        

    LinkButton lb = new LinkButton();
    lb.Text = "Add To Cart";
    //NOTE: if I bind after page load the command never fires.      
    lb.Command +=  new CommandEventHandler(AddItem);
    lb.CommandName = "AddItem";
    lb.CommandArgument = m.Model;        
    ph.Controls.Add(lb);

}

protected void grdProducts_OnSorting(object sender, GridViewSortEventArgs e)
{
    //NOTE: since events fire after page load I can't handle this properly.

    hfSortExpression.Value = e.SortExpression.ToString();

    grdProducts.PageIndex = 0;
    //NOTE: If I rebind here I hose my dynamic controls
    //grdProducts.DataSource = GetDataSource();
    //grdProducts.DataBind();
}

Check this thread, It may give you idea http://stackoverflow.com/questions/5947780/how-to-convert-a-gridview-to-datatable-and-sort-the-datatable/5947912#5947912 — Muhammad Akhtar, May 17 '11 at 16:42

personaelit · Accepted Answer · 2011-05-22T13:25:28.960

1

Well, the answer for me was to rethink how I attacked the problem. I got rid of the dynamic linkbutton and added a button field instead. That way I could bind the gridview where ever and its control state didn't matter. Here is a page that helped me.

http://msdn.microsoft.com/en-us/library/bb907626.aspx

edited May 22 '11 at 13:25

answered May 19 '11 at 16:06

personaelit

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score 0 · Answer 2 · answered May 17 '11 at 16:43

You should write your code in PreRender event of page
ASP.NET Page Life Cycle Overview
PreRender event raised after the Page object has created all controls that are required in order to render the page, including child controls of composite controls.

score 0 · Answer 3 · edited May 17 '11 at 17:16

0

You need to use the OnRowCreated event of the GridView for adding dynamic controls to be able to handle state of them. The OnRowCreated event is fired automatically at every postback, before page load and everytime you call the DataBind() method on the grid.

Only the actual databinding should be in the OnRowDatabound event.

You should also not rebind your grid every postback.

edited May 17 '11 at 17:16

Greg Bacon

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answered May 17 '11 at 16:52

Simon Bondo

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I think this is good advice as a rule, but the command event that I add to the dynamic link button still never fires so I am not sure it solved my problem. Unless I am missing something else. – personaelit May 17 '11 at 17:27
In my particular case, I needed to do this to add a custom filter to the header of each column of the grid. I used the `OnRowCreated` event to create and add a DropDownList and add some filter values to it. When i later needed to add sorting, I sorted the datasource (not the grid itself) and then rebound the grid. – Simon Bondo May 17 '11 at 17:53

score 0 · Answer 4 · answered May 17 '11 at 17:01

Your mistake it that you have to remove these two lines from Page_Load() :

grdProducts.DataSource = GetDataSource();
grdProducts.DataBind();

When I dinamicaly bind datasource on my control, I must override the OnInit like this and take the two line and put it there :

protected override void OnInit(EventArgs e) {
   grdProducts.DataSource = GetDataSource();
   grdProducts.DataBind();
   base.OnInit(e);
}

Then, it maintains states because it's before the initialisation of the ViewState of the page. As Thomas said, get a look at the links he gave you.

Note : Sorry for my english, I'm from Quebec and usualy talk french.

Gridview Sorting and Paging with Dynamically Generated Controls

4 Answers4