Develop Reference

dropdown selected item and repose.redirect

I have two dropdownlist in my project and get the items from sql server. One of them show list of something (And I named it DropdownSoore) and another one show list of members of it (And I named it DropdownAye) that update when select an item from DropdownSoore. then when select an item from DropdownAye go to page of them by forwarding query string. I have no problem to updating DropdownAye but when I select item from it and redirect to page of it, the DropdownAye lose the selected item and show the first item (as default) and index to query string in url.
what should I do?
Excuse me about my grammer, I'm not English...
I set DropdownSoore:
<asp:DropDownList ID="DropDownListSoore" runat="server" class="nav-link btn btn-outline-secondary dropdown-toggle" aria-haspopup="true" aria-expanded="true" AutoPostBack="True"></asp:DropDownList>
for (int i = 0; i <= dt.Rows.Count - 1; i++)
{
string IdSoore = Convert.ToString(dt.Rows[i]["IdSoore"]);
string NameSoore = Convert.ToString(dt.Rows[i]["NameSoore"]);
DropDownListSoore.Items.Add(IdSoore + "." + NameSoore);
}
string forwardedIdSoore = Request.QueryString["IdSoore"];
if (forwardedIdSoore != null)
{
DropDownListSoore.Items.FindByValue(forwardedIdSoore);
}
And then set DropdownAye:
<asp:DropDownList ID="DropDownListAye" runat="server" class="nav-link btn btn-outline-secondary dropdown-toggle" aria-haspopup="true" aria-expanded="true" OnSelectedIndexChanged="DropDownListAye_SelectedIndexChanged" AutoPostBack="True"></asp:DropDownList>
DropDownListAye.Items.Clear();
for (int i = 0; i <= dt1.Rows.Count - 1; i++)
{
DropDownListAye.Items.Add(Convert.ToString(dt1.Rows[i]["NumberAye"]));
}
int iSelectedAye = Convert.ToInt32(DropDownListAye.SelectedIndex) + 1;
string SelectedAye = Convert.ToString(dt1.Rows[iSelectedAye]["IdAye"]);
Session["SSelectedAye"] = SelectedAye;
string forwardedIdAye = Request.QueryString["IdAye"];
if (forwardedIdSoore != null)
{
DropDownListSoore.Items.FindByValue(forwardedIdAye);
}
in page_Load. and dont have problem to update DopdownAye but when I used it to redirect always get IdAye=1 in url and show the first item of DropdownAye ...:
protected void DropDownListAye_SelectedIndexChanged(object sender, EventArgs e)
{
int SelectedAye = Convert.ToInt32(Session["SSelectedAye"]);
int SelectedSoore = Convert.ToInt32(DropDownListSoore.SelectedIndex) + 1;
string forward = "~/contentAye.aspx?IdSoore=" + SelectedSoore + "&IdAye=" + SelectedAye;
Response.Redirect(forward);
}
I try !IsPostBack but dont have utility too.
I do all thing I think and i dont know what shoild i do.

And where are you loading up these infomration?
Remember, page load ALWAYS fires and triggers for each post-back, for each button click, and any OTHER event on the page that calls code behind.
What does the above really mean?
Well, it means that you need to ONLY ONE TIME load up the drop downs, the gridview(s), or whatever else you have.
So, for the last 200+ web pages I have built, I ALWAYS have this code stub in the page load event:
so this markup:
<h3>Select Hotel</h3>
<asp:DropDownList ID="DropDownList1" runat="server"
DataValueField="ID"
DataTextField="HotelName" Width="356px">
</asp:DropDownList>
<br />
<br />
<asp:Button ID="Button1" runat="server"
Text="Show/get/display drop selection" OnClick="Button1_Click"
CssClass="btn" />
<br />
<h3>Selected result</h3>
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
and code behind:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
// load up data, controls etc.
string strSQL =
"SELECT ID, HotelName FROM tblHotelsA ORDER BY HotelName";
DataTable dt = General.MyRst(strSQL);
DropDownList1.DataSource = dt;
DropDownList1.DataBind();
DropDownList1.Items.Insert(0, new ListItem("Please Select Hotel", ""));
}
}
protected void Button1_Click(object sender, EventArgs e)
{
string sResault =
$#"dropdown list value (pkid) = {DropDownList1.SelectedItem.Value}
<br/>
Dropdown list Text (Hotel) = {DropDownList1.SelectedItem.Text}";
Label1.Text = sResault;
}
and the result:
SUPER important:
If I leave out the !IsPostBack test in page load, then for EVERY button click, the dropdown list re-load code will trigger, and runs BEFORE your button stubb, or post back. As a result, I will see/find/get no valid value from the drop down list, since page load ALWAYS runs before the given code stub, and thus if page load "every time" re-loads the data, then it will blow out the choosen value in the drop down list.
So, loading up of grids, data, dropdowns etc. can ONLY occur one time in page load, since page load ALWAYS runs before each button or event code stub you have behind.
If you thus only load up the controls and dropdowns on the first REAL page load, then the values the user selects in those dropdowns should work, but only will work if you ALWAYS include that all important if (!IsPostBack) code stub in your page load event.
Now, of course in place of that button to loadup + display the dropdown list into that label?
Well, of course that button click may well (like often) jump or navigate to another page. So, in place of that code to fill out the selected value(s) into that lable, we could pass the selected value to the next page. And how to do that? Well, you can use session(), you can use parmaters in the URL, or you can even use a post-back URL, and then the WHOLE previous page becomes available (Page.Previous), which then in theory allows you to grab ANY and ALL values from the previous page.
but, say we choose session() to pass the value, then this:
Session["HotelPK"] = DropDownList1.SelectedItem.Value;
Response.Redirect("GridFun3.aspx");

Pass an asp web control as a CommandArgument

In my web app I have a series of ImageButtons. Upon clicking any of these ImageButtons, the ImageButton that was clicked needs to have it's image changed.
I would like one OnClick method that performs its action on the ImageButton that was clicked. Here is my attempt so far:
ASP.NET Code:
<asp:ImageButton ID="ImageToChange1" runat="server" OnClick="ChangeImage" CommandArgument="ImageToChange1"/>
<asp:ImageButton ID="ImageToChange2" runat="server" OnClick="ChangeImage" CommandArgument="ImageToChange2"/>
<asp:ImageButton ID="ImageToChange3" runat="server" OnClick="ChangeImage" CommandArgument ="ImageToChange3"/>
For my C# Code I want to do something like the following:
public void ChangeImage(object sender, CommandEventArgs e)
{
e.CommandArgument.ImageUrl = "~/Images/Penguins.jpg";
}
I'm wondering if there is a more appropriate way to do this than using the "OnClick" event or if I can accomplish this by manipulating "e" or "sender" somehow. Any insight would be greatly appreciated. Thank you.

In your ChangeImage, you can get the CommandArgument and the control as below
public void ChangeImage(object sender, CommandEventArgs e)
{
ImageButton imageButton = sender as ImageButton;
string imageToChange = e.CommandArgument;
//Then you can assign the appropreate image
imageButton.ImageUrl = "~/Images/Penguins.jpg";
}

Session in not passed between pages c#

I'm working with VS 2013 and Mysql, in one of my pages I put select query in a gridview in this view and I have a button for each row so that if I press a row button I have a new window opening that has the colum Id (which is the first colum ) from the gridview.
the grid view button code:
<Columns>
<asp:TemplateField ><ItemTemplate><asp:Button ID="gridbutton" runat="server" Text="Plus de détails" OnClientClick="basicPopup();return false;" RowIndex='<%# Container.DisplayIndex %>' OnClick="button_click" /></ItemTemplate></asp:TemplateField>
</Columns>
the code of the button_click method:
protected void button_click(object sender, EventArgs e)
{
Button gridbutton = sender as Button;
int rowIndex = Convert.ToInt32(gridbutton.Attributes["RowIndex"]);
string n = "l'index" + rowIndex + "";
Session["idProjet"] = GridView1.Rows[rowIndex].Cells[2].Text;
//string idProjet = Convert.ToString(Session["idProjet"]);
// Alert.Show(idProjet);
}
I just used the two last lines to make sure that I'm getting the value, and I'm getting the right value.
And this is the code from the second page where I want to get the session value:
protected void Page_Load(object sender, EventArgs e)
{
string idProjet = Convert.ToString(Session["idProjet"]);
Alert.Show(idProjet);
}
But all I'm getting is an empty result.

In you button code you have both onclientclick and click event.
In you clickclick event I guest you are opening the different page. Note that client click executes first. So the new page already gets opened. Your server side event executes later. That is why the session is not available in the new form.
<asp:Button ID="gridbutton" runat="server" Text="Plus de détails" OnClientClick="basicPopup();return false;" RowIndex='<%# Container.DisplayIndex %>' OnClick="button_click" />
In this case you have to pass the idProject as query string to the new page.

Click Event of Dynamically generated Anchor Not Firing

I have an anchor on Lable Text.I am creating anchor with runat="server" dynamically on click of a button, It gets created as expected. I want to use its click event but it does not fire.
My code :
lblEmail.Text = email + " <a href='#' runat='server' class='crossicon' onclick='removebtn_Click'></a> ";
protected void removebtn_Click(object sender, EventArgs e)
{
}
How Can I create event for this button?I don't want to use JS, as in that case I will have to use a hidden field for new value

Adding markup/text to the label in that way wouldn't add the linkbutton or register the event to the control tree at the server. For that behavior of dynamically adding controls along with the server events to be achieved, you need to register the controls and events (as shown below)
aspx:
<asp:Panel runat="server" id="pnlEmail">
<asp:Label runat="server" id="lblEmail"/>
</asp:Panel>
aspx.cs:
In whichever event, you want to set the label text (along with the link)
lblEmail.Text = email;
LinkButton lnkbtnEmail = new LinkButton();
lnkbtn.Click += lnkbtn_Click;
lnkbtn.Text = "Dynamic Link";
pnlEmail.Controls.Add(lnkbtnEmail);
And the Handler would be
void lnkbtn_Click(object sender, EventArgs e)
{
// code for your dynamically generated link
}

By default, controls use __doPostBack to do the postback to the server. __doPostBack takes the UniqueID of the control (or in HTML, the name property of the HTML element). The second parameter is the name of the command to fire.
<a href='#' runat='server' class='crossicon' href="javascript:void(0);" onclick="__doPostBack('someuniqueid', '');></a>
System.Web.UI.Page already implements the IPostBackEventHandler interface by default, so you don't need to implement it on every page - it's already there.
You can override the RaisePostBackEvent method on the page like this:
protected override void RaisePostBackEvent(IPostBackEventHandler source, string eventArgument)
{
//call the RaisePostBack event
base.RaisePostBackEvent(source, eventArgument);
if (source == SomeControl)
{
//do something
}
}
I hope it will help you.

I don't think so it is created dynamically. Where is ID of that control. You have to Create Server side control and add it into some placeholder/panel e.t.c

Disable Postback on button ASP.NET c#

here is an example of what I am doing
Page Load
{
//Adds items to a panel (not an updatepanel just a normal panel control)
}
protected void btnNexMod_Click(object sender, EventArgs e)
{
// Calls DoWork() and Appends more items to the same panel
}
My problem is that the asp:button is doing a postback as well as calling DoWork()
Therefore, re-calling my page load, re-initializing my panel :(
I want my items that I have added to the panel to stay there!
All help appreciated, not looking for a hand you the answer kind-of deal. Any steps are appreciated thanks!
Here is an exact example of my problem.
protected void Page_Load(object sender, EventArgs e)
{
CheckBox chkbox = new CheckBox();
chkbox.Text = "hey";
chkbox.ID = "chk" + "hey";
// Add our checkbox to the panel
Panel1.Controls.Add(chkbox);
}
protected void Button1_Click(object sender, EventArgs e)
{
CheckBox chkbox = new CheckBox();
chkbox.Text = "hey";
chkbox.ID = "chk" + "hey";
// Add our checkbox to the panel
Panel1.Controls.Add(chkbox);
}
Only thing on the page is a empty panel and a button with this click even handler.
I have also tried this and it still doesn't work. Now its clearing the initial item appended to the panel.
if (!Page.IsPostBack) // to avoid reloading your control on postback
{
CheckBox chkbox = new CheckBox();
chkbox.Text = "Initial";
chkbox.ID = "chk" + "Initial";
// Add our checkbox to the panel
Panel1.Controls.Add(chkbox);
}

If you're adding controls to the Panel dynamically, then you'll have to recreate the controls at every postback, and make sure to assign the same IDs to the controls so that ViewState can populate the values. It's usually best to recreate dynamic content during OnInit, but this can be difficult in some situations.
One of my favorite tools is the DynamicControlsPlaceHolder, because you can add dynamic controls to it and it will persist them automagically, without any additional coding required on the page. Just add controls to it, and it will do the rest.
Here's the link:
http://www.denisbauer.com/Home/DynamicControlsPlaceholder
As for preventing your button from performing a postback, use OnClientClick and return false.
OnClientClick="return false;"

You could use
<asp:LinkButton OnClientClick="javascript:addItemsToPanel();return false;"
thus using a javascript function to add them. That's how I've got around that problem.

You can also try this:
Page Load
{
if (!this.IsPostBack) // to avoid reloading your control on postback
{
//Adds items to a panel (not an updatepanel just a normal panel control)
}
}

you can do like this...
ASPX code:
<asp:LinkButton ID="someID" runat="server" Text="clicky"></asp:LinkButton>
Code behind:
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
someID.Attributes.Add("onClick", "return false;");
}
}
What renders as HTML is:
<a onclick="return false;" id="someID" href="javascript:__doPostBack('someID','')">clicky</a>

You are correct, you will have to add the new items to the Panel after a PostBack. That is the nature of the .NET pipeline.
If you use a data bound control, like a Repeater, to display the panel contents, then the button click handler just needs to rebind the control and it will all work out correctly.

Changing the asp:Button to a asp:LinkButton solved my issue.

I think, it is better use the Ajax Update panel. And put your button in to that.
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button1" />
</ContentTemplate>
</asp:UpdatePanel>