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ASP.Net dynamic control/postback/event-handler madness – Part 2

May 13, 2013 Leave a comment

As a continuation of the HOW I was able to deal with dynamically creating grids based on a query, I had a problem. The problem was that that the ItemCommand was NEVER firing on postback. If you already know where I am going with this, then I’m sorry, but this was a crazy problem that was having a tough time getting to the bottom of. None of my debug code would ever hit or do anything related to that generated command button click, even though the post back happened.

When testing, I also noticed that all of my grids were disappearing on the post back, which made sense, because I had done this is usual:

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindData();
}
}

But, it appears that when the Page_Load fires on the postback and it does NOT create the control that caused the postback in the first place (my grid with a command button), it never fires the event handler! I was able to get it all to work by removing the IsPostBack check, but it seems silly to think that I am recreating the control from scratch in order to fire a button click. Almost like the button that ASP.Net is saying was clicked is gone forever and is replaced by another one which IT thinks was clicked. Kind of bizarre!!

Categories: .Net, Musings, Problems

ASP.Net dynamic control/postback/event-handler madness – Part 1

May 13, 2013 Leave a comment

Well, I recently had a difficult problem that I solved in a way that I don’t really like, but it works all the same. In the process I discovered something bizarre about ASP.Net. Here was the problem: I had a dataset coming out of a SQL stored procedure (that I had no control over or information about, except the output). The dataset needed to be grouped (1 – by period) and subgrouped (2 – by description) based on the properties, then displayed in a table for editing (3), if conditions permitted (4).

I solved these 4 problems with some interesting logic, first based on a container object that I populated out of the database. Then I did the following to solve problem 1:

HashSet periods = new HashSet();
List report = Helper.GetReport();
foreach (objContainer container in report)
{
periods.Add(container.Period);
}

Dictionary<string, List> periodDictionary = new Dictionary<string, List>();
//need to get periods and descriptions within them.
foreach (string period in periods)
{
periodDictionary.Add(period, report.FindAll(p => p.Period == period));
}

This gave me the values broken down into a dictionary of the containers grouped by their period property, but I had to do this again in order to group them again, and then I had to break it down again in order to output the information to the screen. Which, presented a problem, incidentally. I needed a way to display this information in an aspx. So, I just created a div tag with a server side ID value (grids) and then added controls to it, which you’ll see here:

foreach (KeyValuePair<string, List> kvp in periodDictionary)
{
//Okay, broken down by periods now.
//Now we need to break down each value list by description in the same way.

//print header
Label title = new Label();
title.Text = kvp.Key;
title.CssClass = “PeriodHeader”;

grids.Controls.Add(title);

HashSet descriptions = new HashSet();
foreach (objContainer container in kvp.Value)
{
descriptions.Add(container.Desc);
}

Dictionary<string, List> descDictionary = new Dictionary<string, List>();
foreach (string description in descriptions)
{
descDictionary.Add(description, kvp.Value.FindAll(p => p.Desc == description));
}

foreach (KeyValuePair<string, List> kvp2 in descDictionary)
{
Label subtitle = new Label();
subtitle.Text = kvp2.Key;
subtitle.CssClass = “DescHeader”;

grids.Controls.Add(subtitle);
DataGrid grid1 = BuildDataGrid(kvp2.Value);
grids.Controls.Add(grid1);
}
}

I’m sure anyone could pick out issues here, primarly the use of a DataGrid instead of a GridView. I like the DataGrid, okay?!? Get off my case!! Anyway, this worked and allowed me to just generate the information and group it with classes as needed in my BuildDataGrid() method. The specifics aren’t important, but here are a few examples of how I created the grid:

dataSource = dataSource.OrderByDescending(o => o.TransactionDate).ToList();
DataGrid grid = new DataGrid();
grid.DataSource = dataSource;
grid.ItemDataBound += new DataGridItemEventHandler(this.grid_ItemDataBound);
grid.ItemCommand += new DataGridCommandEventHandler(this.Grid_ItemCommand);

grid.AutoGenerateColumns = false;
grid.BorderStyle = BorderStyle.None;

BoundColumn column1 = new BoundColumn();
column1.DataField = “TransactionDate”;
column1.DataFormatString = “{0:MMM dd,yyyy}”;

ButtonColumn column4 = new ButtonColumn();
column4.ItemStyle.CssClass = “editButton”;
column4.DataTextField=”ShowEdit”;
column4.CommandName = “Edit”;
column4.ButtonType = ButtonColumnType.PushButton;

grid.Columns.Add(column1);
grid.Columns.Add(column4);
grid.DataBind();

return grid;

Okay, this long post is getting very long, but the point is that I was able to dynamically generate the columns and buttons and data all on the PageLoad() call and entirely server side. The bolded lines show how I was able to add the event handler code to the grid so that I could get in the way of the binding and the itemCommand events to adjust things as needed (styling, and dynamic commands like delete or edit based on the CommandName).

Categories: .Net, Musings, Problems