Develop Reference

How do you get POSTed value from dynamically populated dropdownlist without the use of UpdatePanel?

I have a Web Form dependent on a Master Page, that contains a simple Form like this:
<asp:TextBox runat="server" ID="txtValue"></asp:TextBox>
<asp:DropDownList runat="server" ID="ddlProduct" />
<asp:Button runat="server" ID="btnConfirm" Text="Confirm" OnClick="btnConfirm_OnClick" />
on Page_Load I dynamically populate the DropDownList with values:
foreach(var product in products)
{
ListItem item = new ListItem(product.Nazev, product.ProductId.ToString());
ddlProduct.Items.Add(item);
}
Now .. normally if the DropDownList was populated statically, I would go with this, to get my selected value out of it:
protected void btnConfirm_OnClick(object sender, EventArgs e)
{
string selectedProduct = ddlProduct.SelectedValue;
}
But this is a no-go in this situation. Hence I try to directly get the selected value from POSTed parameters with one of those approaches (which are in fact practically the same):
protected void btnConfirm_OnClick(object sender, EventArgs e)
{
string selectedProduct = Request.Form.Get(ddlProdukt.ClientID);
string selectedProduct2 = Request.Params[ddlProdukt.ClientID];
}
But it doesn't work. If I debug it, the actual "id/name" of the DropDownList in the POSTed Form (Request.Params) is:
"ctl00$MainContent$ddlProdukt"
whereas the ClientId my approach gives me is:
"ctl00_MainContent_ddlProdukt"
I can't figure out, why does it replace '_' for '$' in the ID of my DDL control.. It seems to be such a trivial thing. There should be a better way to find out the right ID, than replacing the character, right?
Is there some other way I should "look/ask" for the selected value?
*Take into account, that I'am not looking for a solution with an UpdatePanel. I know, that using an UpdatePanel would result in the DDL value being sucessfully selected after the Postback, but that is NOT the answer I'm looking for here.
Thank you for any input.

If you still need to use the Request.Form.Get or Request.Params you should call it on ddlProdukt.UniqueID as it's separator is '$' versus '_' on the .ClientID

As requested an example. This code and the <asp:DropDownList ID="ddlProduct" runat="server"></asp:DropDownList> are on the aspx page, not the Master.
protected void Page_Load(object sender, EventArgs e)
{
//bind data not here
if (IsPostBack == false)
{
//but inside the ispostback check
ddlProduct.Items.Add(new ListItem("Item 1", "1"));
ddlProduct.Items.Add(new ListItem("Item 2", "2"));
ddlProduct.Items.Add(new ListItem("Item 3", "3"));
ddlProduct.DataBind();
}
}
protected void Button1_Click(object sender, EventArgs e)
{
Label1.Text = ddlProduct.SelectedValue;
}

DropDownList not accepting the SelectedIndex im trying to assign

I'm having a hard time figuring this out and I hope you guys would help me.
I have a page called Index.aspx with a DropDownList that is a separate UserControl class (because it will be used in other pages). Here's the code for that:
UcSelecionarLocal.ascx:
<%# Control Language="C#" AutoEventWireup="true"
CodeBehind="UcSelecionarLocal.ascx.cs"
Inherits="QuickMassage.uc.UcSelecionarLocal" %>
<asp:DropDownList ID="ddlLocais" runat="server"
CssClass="span4 dropdown-toggle" AutoPostBack="true">
</asp:DropDownList>
UcSelecionarLocal.ascx.cs:
public partial class UcSelecionarLocal : UserControl {
protected void Page_Load(object sender, EventArgs e) {
if (!this.IsPostBack) {
PreencherLocais();
}
}
private void PreencherLocais() {
ddlLocais.Items.Clear();
ddlLocais.Items.Add(new ListItem("Selecione", "0"));
ControleLocal controle = new ControleLocal();
DataTable tab = controle.ListarLocais();
foreach (DataRow row in tab.Rows) {
ddlLocais.Items.Add(new ListItem(row["Descricao"].ToString(),
row["ID"].ToString()));
}
}
}
This control is placed in Index.aspx and loads its values correctly. The form that it's contained in, has the action set to agendamentos.aspx. When I change the ddlist, the page is submitted to the forms action page, as it should be.
On the other page the problems begin: I get the parameters posted to this page and one of them is the ddlist value. In the immediate window, I check the value and it's there, let's say that it is 1.
To make long story short, I have this code:
agendamentos.aspx.cs:
protected void Page_Load(object sender, EventArgs e) {
DropDownList locais = ObterComponenteListaLocais();
try {
locais.SelectedIndex =
int.Parse(HttpContext.Current.Request["ucSelLocal$ddlLocais"]);
}
While debugging, I see that locais.SelectedIndex is -1. After the assignment it remains -1. The page loads and then I change the ddlist value again to 2. When debugging the same code above, I see that the locais.SelectedIndex is now 1. Again, setting it to 2, as it would normally be, produces no effect. If I change the ddlist again to 3, the SelectedIndex becomes 2 and does not take the value 3.
In other words: the value of the index in a newly loaded page is the value of the page that was loaded before.
Could you guys help me?

This is because the Page_Load event is firing in your page before the user control is loading. Do this:
public partial class UcSelecionarLocal : UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
}
public void PreencherLocais()
{
ddlLocais.Items.Clear();
ddlLocais.Items.Add(new ListItem("Selecione", "0"));
ControleLocal controle = new ControleLocal();
DataTable tab = controle.ListarLocais();
foreach (DataRow row in tab.Rows)
{
ddlLocais.Items.Add(new ListItem(row["Descricao"].ToString(), row["ID"].ToString()));
}
}
}
Then in your aspx page:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
this.idOfYourUserControl.PreencherLocais();
DropDownList locais = ObterComponenteListaLocais();
try {
locais.SelectedIndex =
int.Parse(HttpContext.Current.Request["ucSelLocal$ddlLocais"]);
}
}
Also because your question is a little confusing, an important note is that Page_Load fires before data is captured from controls that post back data. So that's a bad place to get their information because it will be what it was previously. That's why you need to create a function that fires on something like a button click that will execute after the controls data have been loaded.

Dropdownlist SelectedIndexChanged firing on every postback

I am dynamically adding a custom user control to an update panel. My user control contains two dropdownlists and a textbox. When a control outside of the update panel triggers a postsback, I am re-adding the user control to the update panel.
The problem is...on postback when I re-add the user controls, it's firing the "SelectedIndexChanged" event of the dropdownlists inside the user control. Even if the selectedindex did not change since the last postback.
Any ideas?
I can post the code if necessary, but there's quite a bit in this particular scenario.
Thanks in advance!
EDIT...CODE ADDED BELOW
*.ASCX
<asp:DropDownList ID="ddlColumns" OnSelectedIndexChanged="ddlColumns_SelectedChanged" AppendDataBoundItems="true" AutoPostBack="true" runat="server">
*.ASCX.CS
List<dataColumnSpecs> dataColumns = new List<dataColumnSpecs>();
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
fillDDLColumns();
}
}
public void fillDataColumnsList()
{
dataColumns.Clear();
//COMMON GETDATATABLE RETURNS A DATA TABLE POPULATED WITH THE RESULTS FROM THE STORED PROC COMMAND
DataTable dt = common.getDataTable(storedProcs.SELECT_COLUMNS, new List<SqlParameter>());
foreach (DataRow dr in dt.Rows)
{
dataColumns.Add(new dataColumnSpecs(dr["columnName"].ToString(), dr["friendlyName"].ToString(), dr["dataType"].ToString(), (int)dr["dataSize"]));
}
}
public void fillDDLColumns()
{
fillDataColumnsList();
ddlColumns.Items.Clear();
foreach (dataColumnSpecs dcs in dataColumns)
{
ListItem li = new ListItem();
li.Text = dcs.friendlyName;
li.Value = dcs.columnName;
ddlColumns.Items.Add(li);
}
ddlColumns.Items.Insert(0, new ListItem(" -SELECT A COLUMN- ", ""));
ddlColumns.DataBind();
}
protected void ddlColumns_SelectedChanged(object sender, EventArgs e)
{
//THIS CODE IS BEING FIRED WHEN A BUTTON ON THE PARENT *.ASPX IS CLICKED
}
*.ASPX
<asp:UpdatePanel ID="upControls" runat="server">
<ContentTemplate>
<asp:Button ID="btnAddControl" runat="server" Text="+" OnClick="btnAddControl_Click" />
</ContentTemplate>
</asp:UpdatePanel>
<asp:Button ID="btnGo" runat="server" Text="Go" OnClick="btnGo_Click" ValidationGroup="vgGo" />
<asp:GridView...
*.ASPX.CS
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
uc_Counter = 0;
addControl();
gridview_DataBind();
}
else
{
reloadControls();
}
}
protected void btnGo_Click(object sender, EventArgs e)
{
if (Page.IsValid)
{
//THIS BUTTON CLICK IS WHAT'S TRIGGERING THE
//SELECTEDINDEXCHANGED EVENT TO FIRE ON MY *.ASCX
gridview_DataBind();
}
}
private void reloadControls()
{
int count = this.uc_Counter;
for (int i = 0; i < count; i++)
{
Control myUserControl = Page.LoadControl("~/Controls/myUserControl.ascx");
myUserControl.ID = "scID_" + i;
upControls.ContentTemplateContainer.Controls.AddAt(i, myUserControl);
((customUserControl)myUserControl).fillDDLColumns();
}
}
private void addControl()
{
Control myUserControl = Page.LoadControl("~/Controls/myUserControl.ascx");
myUserControl.ID = "scID_" + uc_Counter.ToString();
upControls.ContentTemplateContainer.Controls.AddAt(upControls.ContentTemplateContainer.Controls.IndexOf(btnAddControl), myUserControl);
//((customUserControl)myUserControl).fillDDLColumns();
this.uc_Counter++;
}
protected int uc_Counter
{
get { return (int)ViewState["uc_Counter"]; }
set { ViewState["uc_Counter"] = value; }
}

Even though this is already answered I want to put an answer here since I've recently tangled with this problem and I couldn't find an answer anywhere that helped me but I did find a solution after a lot of digging into the code.
For me, the reason why this was happening was due to someone overwriting PageStatePersister to change how the viewstate hidden field is rendered. Why do that? I found my answer here.
One of the greatest problems when trying to optimize an ASP.NET page to be more search engine friendly is the view state hidden field. Most search engines give more score to the content of the firsts[sic] thousands of bytes of the document so if your first 2 KB are view state junk your pages are penalized. So the goal here is to move the view state data as down as possible.
What the code I encountered did was blank out the __VIEWSTATE hidden fields and create a view_state hidden field towards the bottom of the page. The problem with this is that it totally mucked up the viewstate and I was getting dropdownlists reported as being changed when they weren't, as well as having all dropdownlists going through the same handler on submit. It was a mess. My solution was to turn off this custom persister on this page only so I wouldn't have to compensate for all this weirdness.
protected override PageStatePersister PageStatePersister
{
get
{
if (LoginRedirectUrl == "/the_page_in_question.aspx")
{
return new HiddenFieldPageStatePersister(Page);
}
return new CustomPageStatePersister(this);
}
}
This allowed me to have my proper viewstate for the page I needed it on but kept the SEO code for the rest of the site. Hope this helps someone.

I found my answer in this post .net DropDownList gets cleared after postback
I changed my counter that I was storing in the viewstate to a session variable.
Then I moved my reloadControls() function from the Page_Load of the *.ASPX to the Page_Init.
The key was dynamically adding my user control in the Page_Init so it would be a member of the page before the Viewstate was applied to controls on the page.

HtmlInputCheckBox in Repeater always not checked

i'm using a HtmlInputCheckBox in a repeater by adding
<input id="CheckBox1" type="checkbox" runat="server" value='<%# Eval ("userid") %>' />
to repeater->ItemTemplate->table->tr->td and in the server side i'm using
protected void Button1_Click(object sender, EventArgs e)
{
for (int i = 0; i < UserRepeater.Items.Count; i++)
{
var chkBox = UserRepeater.Items[i].FindControl("CheckBox1") as HtmlInputCheckBox;
if (chkBox != null && chkBox.Checked)
{
//
}
}
}
i'm not programatically setting any checkbox to set - i'm checking them on the web page during test.
my var checkbox is always inchecked {Value = "1,2,3,4" Checked = false}, thx for helping me with that.

How are you populating your repeater - if you are doing it in page_load make sure it is protected for postbacks:
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
// populate your data
}
}
EDIT
This is assuming you are working with viewstate on - which is the case by default.

This may be to do with when you bind your repeater. If you are binding on Page_Load, the check boxes will be created after viewstate and post variables have been restored, so the value won't be on your checkboxes.
If possible, move the data bind to Page_Init; as this happens before viewstate/post values are restored your checkboxes will get the right values assigned. If you can't bind on Page_Init, then #Aristos's answer will do.

End user add values to a dropdownlist?

I'm populating a dropdownlist in c# asp.net-MVC from a SQL table using Linq2Sql. I'd like for the user to be able to enter something that isn't in the list into the drop down and have it add to the table. Is this possible?

Sounds like you need to add a radio button labeled "Other". When the user clicks the radio button a text box would appear that allows the user to input a new value that you can save to your DB and display in the drop down.
EDIT:
Quick snippet to enable the control using JavaScript:
<script language="javascript" type="text/javascript">
function radioclicked() {
textObj = document.getElementById('<NAME OF TEXT BOX');
textObj.disabled = false;
}
</script>
You can use a check box instead of a radio button so that the enabled property can be toggled.
To completely hide the text box then you will have to look into jQuery/Ajax.

Why can't we use a lightweight Add-on like www.combodropdown.info for this purpose? You can even consider AutoComplete plugin from jQuery, if your app already references jQuery.

Also a combobox will allow a user to enter a value in addition to picking from a list.

My MVC is not so so, but I assume this still applies as MVC is just model view controller.
What if you throw a drop down on your form visible=true, and a textbox on your form visible =false.
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
onselectedindexchanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
<asp:TextBox ID="TextBox1" runat="server" Visible="False"></asp:TextBox>
Fill your drop down:
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
List<int> s = Enumerable.Range(1, 10).ToList();
DropDownList1.DataSource = s;
DropDownList1.DataBind();
DropDownList1.Items.Add("Other");
}
}
Add an event to handle if someone selects other. If they do make the textbox visible:
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
switch (this.DropDownList1.SelectedItem.Text)
{
case "Other":
this.TextBox1.Visible=true;
break;
default:
this.TextBox1.Visible=false;
break;
}
}
Now you can enter your value and re-store back to the db.