Develop Reference

Datagrid ItemCommand event not firing

I am still a novice with asp.net, so I'm sure there are better ways to do some of this...
I want to allow a user to enter a date, and then execute an SQL query against a database to return all records matching that date. I want to display those records, and allow the user to select one for additional processing. It seemed like the DataGrid with a column of Pushbuttons was a good choice. In fact, I've done this before, but it those cases there was no user interaction involved. The page just ran a fixed SQL query. With what I'm doing now, the data is displayed as I want, but the Pushbuttons aren't working...the ItemCommand event doesn't fire.
I've read a lot of threads about the ItemCommand event not firing, but I still can't get this to work. My understanding is that I need to bind the DataGrid while not in a Postback, and I think my code does that. When I debug the Page_Load event, I can see that the code inside if (!IsPostBack){} is running, and the session variables have the expected data.
On the page that hosts the DataGrid, I have a 'Find' button that executes a SQL query against a database. The query uses a date entered into the textbox that is on that page. In the 'Find' button click event, I store the results of the query (a DataTable) in a session variable, then do a Redirect to re-load the page.
Once the page reloads, the session variables contain my expected data and the data is displayed in the DataGrid, along with the Pushbuttons. When I click any of the buttons in the DataGrid, the contents of the DataGrid disappear and the ItemCommand event does not fire.
Here's the definition of the DataGrid (updated to include the button):
<asp:Panel runat="server" ID="pnlSelect" HorizontalAlign="Left" Visible="true" style="margin-top:10px" >
Please select a participant.
<asp:DataGrid runat="server" ID="grdItems" AutoGenerateColumns="true" BorderColor="black" BorderWidth="1" CellPadding="3" style="margin-left:2px; margin-top:6px" OnItemCommand="grdSelect_ItemCommand" >
<Columns>
<asp:ButtonColumn HeaderStyle-HorizontalAlign="Center" ButtonType="PushButton" Text="Select" HeaderText="Select" CommandName="Select" >
<ItemStyle Width="60px" HorizontalAlign="Center"/>
</asp:ButtonColumn>
</Columns>
</asp:DataGrid>
</asp:Panel>
Here's the Page Load code (unneeded code-behind stuff is commented out):
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
if (Session["y"] != null)
{
txtFind.Text = Session["x"].ToString();
DataTable table = Session["y"] as DataTable;
Session.Remove("x");
Session.Remove("y");
if (table != null)
{
/*
ButtonColumn buttonColumn = new ButtonColumn
{
HeaderText = "Select",
Text = "Select",
CommandName = "Select",
ButtonType = ButtonColumnType.PushButton,
};
grdItems.Columns.Add(buttonColumn);
foreach (DataColumn c in table.Columns)
{
BoundColumn column = new BoundColumn
{
HeaderText = c.Caption,
DataField = c.Caption,
ReadOnly = true
};
grdItems.Columns.Add(column);
}
*/
grdItems.DataSource = table;
grdItems.DataBind();
}
}
}
}
Here's the relevant 'Find' button event code. I can't post the details of the sql query text, but that part does work and the DataTable does contain the expected data:
DataTable table = DatabaseHelper.FindBySQL(sqlText);
if (table != null && table.Rows.Count > 0)
{
Session["x"] = searchtext;
Session["y"] = table;
Response.Redirect(Request.RawUrl, true);
}
And this the ItemCommand event. I place a breakpoint on the first line, and the debugger never hits it.
protected void grdItems_ItemCommand(object source, DataGridCommandEventArgs e)
{
string item = "";
switch (e.CommandName.ToLower())
{
case "select":
item = e.Item.Cells[1].Text.Trim();
//todo: handle the selected data
break;
}
}
Thanks for any thoughts.
Don

asp.net: How to update data in GridView through Checkbox in particular row

I am developing a Web Form, where I show Gridview with data. One of the column consists of CheckBox. How can I update data in particular row.
so my question is:
How to unidentified particular row and send an sql request with UPDATE when user Check or Uncheck the CheckBox?
Update:
Here is my code that i have. It doesn't update value of CheckBox.
namespace:
public partial class Call_Bills : System.Web.UI.Page
{
SqlConnection con = new SqlConnection();
string check;
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Button_Submit(object sender, EventArgs e)
{
foreach (GridViewRow row in GridView2.Rows)
{
con.ConnectionString = ConfigurationManager.ConnectionStrings["TestDeductionsConnectionString2"].ToString();
con.Open();
bool private1 = (row.FindControl("CheckBox1") as CheckBox).Checked;
if (private1 == true)
{
check = "1";
}
else
{
check = "0";
}
SqlCommand cmd = new SqlCommand("insert into DetailCosts(private) values(#private)", con);
cmd.Parameters.AddWithValue("#private", check);
cmd.ExecuteNonQuery();
}}
name of GridView is: GridView2;
name of Checkbox in the Table: private;
id of CheckBox in Gridview is:
<asp:TemplateField HeaderText="Private" SortExpression="private">
<ItemTemplate>
<asp:CheckBox ID="CheckBox1" runat="server" Checked='<%# Eval("private") %>' />
</ItemTemplate>
<HeaderStyle HorizontalAlign="Center" />
</asp:TemplateField>

you can manually define a method to handle a postback generated by a control inside a gridview column. To do that you just need to add the tags AutoPostBack=True and OnCheckedChanged=YourMethodName to the control.
On the code-behind, define this method as public void, and define the parameters that usually would be there (sender as object and e as EventArgs), like:
public void YourMethodName(object sender, EventArgs e)
On the method, you may need to get the GridViewRow which contains the control that has generated the event. To do that, just parse the sender parameter (which will be the checkbox) and get 2 parent levels (GridViewCell and GridViewRow), it would be something like:
GridViewRow row = ((CheckBox)sender).parent.parent;
Since you have the row, you may get any control inside it with the FindControl method. If you need an id to identify the entitiy being updated, you may store it in a hidden field inside the row.
Hope it helps!

Gridview Row Events not firing in UserControl

I've got a pretty strange problem with my usercontrols that I'm working with. I'm coding some user controls to be used in a DotNetNuke module.
Basically I have a UserControl on my page that holds some controls and then there is a Placeholder where I am loading in a UserControl that has a GridView placed in it.
Basically here is my page structure
<asp:Panel runat="server" ID="pnlServiceType" Visible="false">
<uc:ServiceType runat="server" ID="ServiceType" />
</asp:Panel>
Within that user control are some form elements and then the following:
<asp:PlaceHolder runat="server" ID="phServices" />
That placeholder then has a user control added to it like so:
<p class="header"><asp:Label runat="server" ID="lblServiceHeader" Font-Bold="true" /></p>
<asp:GridView runat="server" ID="gvServices" AlternatingRowStyle-BackColor="#eaeaea" BorderStyle="None" GridLines="None"
AutoGenerateColumns="false" CellPadding="6" Width="100%" EnableViewState="false" OnRowEditing="gvServices_RowEditing">
When the user picks something in the DropDownList, I'm clearing the controls out of the Placeholder, and re-adding just a single UserControl for the set of records for whatever type they've picked like so
_serviceID = e.Value;
//Clear the controls out of the placeholder
phServices.Controls.Clear();
//Reset the count of grids for the OnInit() method
Session["GridCount"] = 0;
if (e.Value != "NULL")
{
PopulateServicesGrid(_service.GetServicesByFormType(Convert.ToInt32(e.Value)));
}
else
{
PopulateServicesGrid(_service.GetServicesByClient(Convert.ToInt32(_client)));
}
And the PopulateServicesGrid method:
private void PopulateServicesGrid(List<NOAService> services)
{
//Creates a LINQ grouping based on the Billing Codes
//Allows a super easy creation of grids based on the grouped billing codes
var query = services.Select(service => service.BillingCode).Distinct();
foreach (string code in query)
{
var servicesByCode = services.Where(service => service.BillingCode == code).ToList();
ServicesGrid servicesGrid = LoadControl("~/DesktopModules/LEL Modules/NOA/ServicesGrid.ascx") as ServicesGrid;
Label lblServiceHeader = servicesGrid.FindControl("lblServiceHeader") as Label;
GridView gvServices = servicesGrid.FindControl("gvServices") as GridView;
phServices.Controls.Add(servicesGrid);
servicesGrid.ID = code;
lblServiceHeader.Text = servicesByCode[0].FormTypeName;
gvServices.DataSource = servicesByCode;
gvServices.DataBind();
Session["GridCount"] = phServices.Controls.Count;
}
}
And on my ServiceType UserControl, on the PageInit, I'm readding the ServiceGrid usercontrol so that my grids show up across postbacks and aren't lost from the Placeholder
void NOAServiceType_Init(object sender, EventArgs e)
{
for (int i = 0; i < Convert.ToInt32(Session["GridCount"]); i++)
{
ServicesGrid servicesGrid = LoadControl("~/DesktopModules/LEL Modules/NOA/ServicesGrid.ascx") as ServicesGrid;
phServices.Controls.Add(servicesGrid);
}
}
The grids populate successfully and everything seems to work just fine. But for some reason, on my GridView, I have a CommandField of
<asp:CommandField ShowEditButton="true" ItemStyle-HorizontalAlign="Right" EditText="Edit" UpdateText="Update"
EditImageUrl="~/images/LELModules/appbar.edit.rest.png" CancelImageUrl="~/images/LELModules/appbar.close.rest.png" UpdateImageUrl="~/images/LELModules/appbar.check.rest.png"
ButtonType="Image" CausesValidation="false" />
When I click my Edit command on the Grid row, nothing happens. My grid doesn't lose its rows, the control is still there, everything seems like it should be ok. The RowEditing event doesn't fire until I click it a second time.
Any idea why this might be occuring?
UPDATE: I've managed to figure out that my SelectedIndexChanged handlers are effectively resetting the DataSource on the Grid contained by the UserControl when they are readded to the PlaceHolder. When the CommandField (Edit) is clicked though, the Init fires for the UserControl that holds the placeholder
ServiceType UserControl < `Init` fires here
-Form elements
-Placeholder which holds
--UserControl with GridView
The Init method loads up new instances of the UserControl and adds them to the PlaceHolder, but the DataSource is null. With EnableViewState=true it looks like the data is still bound, but if I handle PreRender, I can see that the DataSource on my gvServices | null
Is it even possible to edit rows like this on a GridView that is being added dynamically to a PlaceHolder over and over?
FIXED I found out what the issue was after referring to this article
http://www.west-wind.com/weblog/posts/2006/Feb/24/Overriding-ClientID-and-UniqueID-on-ASPNET-controls
It got me thinking, what if the IDs were getting changed? The controls are way nested. So I went and put a watch on the GridView's ID, ClientID, and UniqueID just to see. When the Control is loaded on my Init handler, it's assigned a super generic ID when it's added.
private void PopulateServicesGrid(List<NOAService> services)
{
//Creates a LINQ grouping based on the Billing Codes
//Allows a super easy creation of grids based on the grouped billing codes
var query = services.Select(service => service.BillingCode).Distinct();
foreach (string code in query)
{
var servicesByCode = services.Where(service => service.BillingCode == code).ToList();
ServicesGrid servicesGrid = LoadControl("~/DesktopModules/LEL Modules/NOA/ServicesGrid.ascx") as ServicesGrid;
Label lblServiceHeader = servicesGrid.FindControl("lblServiceHeader") as Label;
GridView gvServices = servicesGrid.FindControl("gvServices") as GridView;
phServices.Controls.Add(servicesGrid);
**servicesGrid.ID = code;**
lblServiceHeader.Text = servicesByCode[0].FormTypeName;
gvServices.DataSource = servicesByCode;
gvServices.DataBind();
Session["GridCount"] = phServices.Controls.Count;
}
}
I was setting the ID as something else. So when I was hitting the Edit RowCommand on my grid, it was reloading the controls again on Init and the IDs were being changed back from my custom set code (T2020, pulled from my database) to the generic ID again, it didn't know how to fire the event.
I hope this helps someone as I've lost at least 12 hours fixing this problem.

ASP.NET: Dynamically creating controls

I have the following scenario:
My page has a dropdown list that allows user to choose a category.
For each category, there is a set of attributes, whose values should be fetched from the user. The number of attributes are different for each category.
Depending on the category the user chooses, a set of dropdown lists should be created corresponding to the attributes and filled with corresponding attribute values.
Since it is required that the page should not reload, I plan to fetch the data (from SQL Server 2008) using AJAX (?). I'm new to ASP.NET and have not used AJAX though I'm comfortable with C#. Need advice on how to proceed.
EDIT: Is this useful if I need to dynamically generate combo boxes?

You can use UpdatePanel or PageMethods
in both cases and in any case, I would say, you do need to know JavaScript when you want to use AJAX and make dynamic web applications. It take some time but it pays off don't worry.
you can search here in SO about PageMethod, for example see this one:
Regarding PageMethod in asp.net

You could use the following approach (if you do not feel comfortable building a more complex UI with javascript).
It works by dynamically creating the attribute DropDownLists when the page loads (you would implement it based on the result of a DB query) and hiding each one, ready for display later on.
Upon the selection of a category the correct DropDownLists would then be made visible (again a query here could determine which attribute DropDownLists become visible).
Obviously it will require some modifications to probably generate a Panel which contains each DropDownList and a Label control, instead of just creating a number of DropDownLists.
You would then show/hide the Panel instead of the DropDownList, but hopefully it points you in the right direction.
Hope this helps.
Markup
<style type="text/css">
select
{
display:block;
margin-top:10px;
}
</style>
....
<asp:ScriptManager ID="scriptManager" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="updatePanel" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<!-- Category selection -->
<asp:DropDownList ID="categoryDropDownList" runat="server" AutoPostBack="true" OnSelectedIndexChanged="categoryDropDownList_SelectedIndexChanged">
<asp:ListItem Text="Please select a category" Value="0"></asp:ListItem>
</asp:DropDownList>
<br />
<!-- Used to store the drop downs -->
<asp:Panel ID="dropDownContainer" runat="server"></asp:Panel>
</ContentTemplate>
</asp:UpdatePanel>
Code
protected void Page_Load(object sender, EventArgs e)
{
LoadDropDownLists();
}
private void LoadDropDownLists()
{
//Dummy data, you would pull your categories/attributes from whichever datasource
//you are using
var categories = new[]{
new { Name = "Category 1", Id = 1, Attributes = new string[]{"GA", "FA", "RA"} },
new { Name = "Category 2", Id = 2, Attributes = new string[]{"GA", "NA"} }
};
//Loop through the categories, load the dropdown
foreach (var category in categories)
{
if (!IsPostBack)
categoryDropDownList.Items.Add(new ListItem(category.Name, category.Id.ToString()));
//For each attribute create a drop down and populate with data as required
foreach (var attribute in category.Attributes)
{
string dropDownListId = FormatDropDownListId(attribute);
if (!DropDownListExists(dropDownListId))
{
DropDownList dropDownList = new DropDownList();
dropDownList.ID = dropDownListId;
dropDownList.Visible = false;
dropDownList.Items.Add(new ListItem(attribute));
dropDownContainer.Controls.Add(dropDownList);
}
}
}
}
private bool DropDownListExists(string id)
{
DropDownList dropDownList = (DropDownList)dropDownContainer.FindControl(id);
return dropDownList != null;
}
protected void categoryDropDownList_SelectedIndexChanged(object sender, EventArgs e)
{
//Reset all visible dropdowns
HideAllDropDownLists();
//Get the selected category
string selectedItem = categoryDropDownList.SelectedItem.Value;
switch (selectedItem)
{
case "1":
{
//Here you would connect to db and pull correct attributes
//then set the visible dropdowns as required
SetDropDownVisibility(FormatDropDownListId("GA"));
SetDropDownVisibility(FormatDropDownListId("FA"));
SetDropDownVisibility(FormatDropDownListId("RA"));
} break;
case "2":
{
SetDropDownVisibility(FormatDropDownListId("GA"));
SetDropDownVisibility(FormatDropDownListId("NA"));
} break;
}
}
private void SetDropDownVisibility(string id)
{
DropDownList dropDownList = (DropDownList)dropDownContainer.FindControl(id);
if(dropDownList != null)
dropDownList.Visible = true;
}
private void HideAllDropDownLists()
{
foreach (Control control in dropDownContainer.Controls)
{
control.Visible = false;
}
}
private string FormatDropDownListId(string id)
{
return string.Format("dropDown{0}", id);
}

If you're using ASP.NET webforms then I don't believe you need to use AJAX or JavaScript.
I would do the following
Set autopostback = true on your combobox
Add an event handler for the OnChanged event of the combobox
Inside the event handler, apply rules at to load / generate / populate child comboboxes
Add those combo boxes to the form
You can either hide the comboboxes (as I see in #jdavies answer), or start without any and dynamically create & add them to the form.
This question deals with the same issue:
DropDownList and Update Panel

Passing two values through CommandArgument and splitting it

I'm using the commandArgument property of the LinkButton ( Which is wrapped inside a repeater ) to pass two values -as one string- to a second repeater then I try to split them into two values, So I could use them as parameters in my ADO.NET Code (SqlCommand Parameters)....after testing my queries don't return any results but If I passed fixed values for the parameter or change the source of the parameter (just for test from a textbox or querystring or something) I get my results, so I think the problem is in splitting.
I Conduct some arugment values from the ArgumentCommand property of the LinkButton -which is wrapped inside a repeater:
<ItemTemplate>
<asp:LinkButton id="sort_lnkbtn" Text='<%# Eval("value")%>'
CommandArgument='<%#string.Format("{0}|{1}",Eval("arrange_by_id"),Eval("value"))%>' runat="server">
</asp:LinkButton>
</ItemTemplate>
Then I receive these values and cut them into two pieces of information:
string sortByAndArrangeBy = (e.CommandArgument).ToString();
char[] separator = { '|' };
string[] sortByAndArrangeByArray = sortByAndArrangeBy.Split(separator);
Now the ado.net code uses this values as a
using (SqlConnection cn1 = new SqlConnection(ConfigurationManager.ConnectionStrings["testConnectionString"].ConnectionString))
{
using (SqlCommand cm1 = new SqlCommand("SELECT [name] FROM brands WHERE (name like #SearchString + '%' )", cn1))
{
cm1.Parameters.Add("#SearchString", System.Data.SqlDbType.Char);
cm1.Parameters["#SearchString"].Value = sortByAndArrangeByArray[1];
cn1.Open();
using (SqlDataReader dr1 = cm1.ExecuteReader())
{
List_rpt.DataSource = dr1;
List_rpt.DataBind();
}
}
}

Here is a simple solution:
Wrap your item template for the repeater in a control. The control will have the same markup as your item template without the bindings:
Control Markup:
<div>
<asp:LinkButton ID="LnkBtnSort" runat="server" Text="Sort" OnClick="LnkBtnSort_Clicked"/>
</div>
Control Code:
public class SomeControl
{
public event EventHandler Click;
public string ArrangeById
{
set { ViewState["byid"] = value; }
get { return ViewState["byid"].ToString(); }
}
public string Value
{
set { ViewState["val"] = value; }
get { return ViewState["val"].ToString(); }
}
protected void LnkBtnSort_Clicked(object sender, EventArgs e)
{
if( Click != null )
{
this.Click(this, EventArgs.Empty);
}
}
}
So now in the repeater all you have to do is bind an instance of that control to the Container.DataItem:
<ItemTemplate>
<ctrl:SomeControl
ID="someControl"
runat="server"
OnClick="SomeControl_Clicked"
ArrangeById='<%# Eval("arrange_by_id") %>'
Value='<%# Eval("value") %>' />
</ItemTemplate>
The page/control that has the repeater will have one simple method:
protected void SomeControl_Clicked(object sender, EventArgs e)
{
//Here cast the sender to the type of control you made:
SomeControl ctrl = (SomeControl)sender;
string byId = ctrl.ArrangeById;
string val = ctrl.Value;
}
Note: this code may not be 100% correct but it illustrates the point. The flow is simple - the control binds its public properties to whatever you need to bind. When the link is clicked (inside your control) the control doesn't propagate this event to the page. Instead it fires its own event (Click) thus sending a signal to the page that an event occured. however by doing so, it changes the source of the event to itself instead of the actual link button. The page handles the event and everyone is happy.
This way you don't have to care what the CommandArgument is... If this comes up empty, it means that either your data source is empty... or something else happened in the code.