Develop Reference

Display calculated value of 2 textbox values to third textbox

I have calculated the two textbox values and displayed successfully it into third textbox but the issues are when I enter value to textbox1 and move to textbox2 the page get reload as I have mentioned AutoPostBack="true" for textbox1 and textbox2 and when I remove this AutoPostBack="true" the calculated value is not displayed in third textbox.
Here is my code behind
protected void txttotal_TextChanged(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(txttotal.Text) && !string.IsNullOrEmpty(txtdiscount.Text))
txtgrandtotal.Text = (Convert.ToInt32(txttotal.Text) - Convert.ToInt32(txtdiscount.Text)).ToString();
}
protected void txtdiscount_TextChanged(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(txttotal.Text) && !string.IsNullOrEmpty(txtdiscount.Text))
txtgrandtotal.Text = (Convert.ToInt32(txttotal.Text) - Convert.ToInt32(txtdiscount.Text)).ToString();
}
Here is aspx code
<asp:TextBox ID="txttotal" runat="server" CssClass="textstyle" OnTextChanged="txttotal_TextChanged" AutoPostBack="true"></asp:TextBox>
<asp:TextBox ID="txtdiscount" runat="server" CssClass="textstyle" OnTextChanged="txtdiscount_TextChanged" AutoPostBack="true"></asp:TextBox>
<asp:TextBox ID="txtgrandtotal" runat="server" CssClass="textstyle" ReadOnly="true"></asp:TextBox>

To add the two text box value and show it on third text box you can add them on button click event here is the code
aspx page
<div>
<asp:TextBox runat="server" ID="txt1"></asp:TextBox>
<asp:TextBox runat="server" ID="txt2"></asp:TextBox>
<br />
<asp:Label runat="server" Text="Answer"></asp:Label> <asp:TextBox runat="server" ID="txt3"></asp:TextBox>
<asp:Button runat="server" ID="btn1" Text="CLICK TO ADD" OnClick="btn1_Click"/>
</div>
.cs
protected void btn1_Click(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(txt1.Text) && !string.IsNullOrEmpty(txt2.Text))
{
txt3.Text = (Convert.ToInt32(txt1.Text) + Convert.ToInt32(txt2.Text)).ToString();
}
else {
Response.Write("Please Enter Value");
}
}

asp.net checkbox with OnClick="return false" (<== read only). How to change to "return true" (<== can write) and back in code behind

I have an asp:checkbox with OnClick="return false" which 'closes' it for changes (that's the nearest equivalent to ReadOnly=true which I found).
I also have a button.
When I click the button I need the codebehind (C#) to change the checkbox to "return true", that is : to 'open' it for checking or unchecking. Clicking the button again should 'close' it back again.
In short - how do I toggle between these two states in the code behind?
HTML:
<asp:Button runat="server" ID="my_Button" Text="click me" OnClick="my_Button_Click" />
<asp:CheckBox runat="server" ID="my_CheckBox" Checked="true" OnClick="return false;" />
Code behind:
protected void my_Button_Click(object sender, EventArgs e)
{
// here is where the toggling should come... <============
}

As you can see here: OnClick vs OnClientClick for an asp:CheckBox? - there's no OnClick for checkbox. You should use OnCheckedChanged instead.
I've attached a minor fix to the problem:
<asp:Button runat="server" ID="my_Button" Text="click me" OnClick="my_Button_Click" />
<asp:CheckBox runat="server" ID="my_CheckBox" Checked="true" OnCheckedChanged="my_checkbox_click" />
And the code behind:
protected void my_checkbox_click(object sender, EventArgs e)
{
}
protected void my_Button_Click(object sender, EventArgs e)
{
my_CheckBox.Enabled = !my_CheckBox.Enabled;
}

In order to achieve this, I added a HiddenField and used it in the code behind.
HTML:
<asp:HiddenField runat="server" ID="my_Hidden_Field" Value="readonly" />
<asp:Button runat="server" ID="my_Button" Text="click me" OnClick="my_Button_Click" />
<asp:CheckBox runat="server" ID="my_CheckBox" Checked="true" OnClick="return false;" />
Code behind:
protected void my_Button_Click(object sender, EventArgs e)
{
if (my_Hidden_Field.Value == "readonly")
{
my_Hidden_Field.Value = "canwrite";
my_CheckBox.Attributes.Add("onclick", "return true;");
}
else
{
my_Hidden_Field.Value = "readonly";
my_CheckBox.Attributes.Add("onclick", "return false;");
}
}
(like always, I look for a solution for a day or two, give up, post a question here, and then I come up with an answer... Hope this will be helpful to others :-)

ASP.NET checkbox autopostback not working

I designed a simple page with, two text boxes, one checkbox, one button, and one label.
When I start I want to check the checkbox to make the button enabled, and then enter two numbers into the two textboxes, click the button to do addition, and show the result in the label.
But when I click the checkbox the page postback is not working; it's not writing Page is posted back on the page and the button is still disabled.
However, if I make the button enabled and do the addition it invokes the page postback and also invokes the checkedchanged method.
<asp:TextBox ID="txtFirst" runat="server"></asp:TextBox>
<asp:TextBox ID="txtSecond" runat="server"></asp:TextBox>
<asp:Label ID="result" runat="server"></asp:Label>
<td>
<asp:CheckBox ID="cboptions" runat="server" AutoPostBack="True"
onCheckedChanged="cboptions_CheckedChanged" />
</td>
<asp:Button ID="submit" runat="server" Text ="addition" onclick="Button_Click"/>
Code:
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == true)
{
Response.Write("Page is posted back");
}
}
protected void cboptions_CheckedChanged(object sender, EventArgs e)
{
submit.Enabled = cboptions.Checked;
}
protected void submit_Click(object sender, EventArgs e)
{
int a = Convert.ToInt32(txtFirst.Text);
int b = Convert.ToInt32(txtSecond.Text)+a;
result.Text = b.ToString();
}

There were many formatting errors in your code, do it this way
Aspx
<asp:TextBox ID="txtFirst" runat="server"></asp:TextBox>
<asp:TextBox ID="txtSecond" runat="server"></asp:TextBox>
<asp:Label ID="result" runat="server"></asp:Label>
<asp:CheckBox ID="cboptions" runat="server" AutoPostBack="True"
onCheckedChanged="cboptions_CheckedChanged" />
<asp:Button ID="btn" runat="server" Text ="addition" onclick="Button_Click"/>
C#
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == true)
{
Response.Write("Page is posted back");
}
}
protected void cboptions_CheckedChanged(object sender, EventArgs e)
{
btn.Enabled = cboptions.Checked;
}
protected void Button_Click(object sender, EventArgs e)
{
int a = Convert.ToInt32(txtFirst.Text);
int b = Convert.ToInt32(txtSecond.Text) + a;
result.Text = b.ToString();
}

How to pass variable from textbox to code behind back to same page

I have a webs form page and I have a text box which once clicked passes a variable to the code behind and then back into another element of that page and I cannot get it to work.
This is the closest I have got.
<asp:Panel ID="Search" runat="server" Visible="true">
<tr>
<td>
<asp:Label ID="lblSearch" runat="server" Text="Search"></asp:Label>
</td>
<td>
<asp:TextBox ID="search" runat="server" />
</td>
<td>
<asp:RequiredFieldValidator ID="valSearch" runat="server"
ControlToValidate="movieSearch" Text="Please enter text" />
</td>
<td>
<asp:Button ID="btnSubmit" runat="server" Text="Save"
OnClick="btnSubmit_Click" />
</td>
</tr>
</table>
</asp:Panel>
<asp:Panel ID="pnlSearchResult" runat="server" Visible="false">
<script>
var search = '<%=Server.UrlDecode(Request.QueryString["Data"]) %>';
</script>
</asp:Panel>
And the code behind:
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (IsValid)
{
pnlSearch.Visible = false;
pnlSearchResult.Visible = true;
Response.Redirect("search.aspx?Data=" + Server.UrlEncode(search.Text));
}
}
Also this does not change the visibility of the two panels for some reason.
I would appreciate any guidance I am very new to asp and c#.

The panel's visibility is not changing because you're forcing a new GET request to the page with this: -
Response.Redirect("search.aspx?Data=" + Server.UrlEncode(search.Text));
(I'm assuming your page is called 'search.aspx')
There's no need to do this. Remove this line.
Secondly, I see you want to force the textbox's Text value into a Javascript variable. Replace this
var search = '<%=Server.UrlDecode(Request.QueryString["Data"]) %>';
with this
var search = '<%= search.Text %>';

Write below code on page event.
Another more important point is you first panel Id is "Search" not "pnlSearch" on aspx page so please correct it
protected void Page_Load(object sender, EventArgs e)
{
if (Request.QueryString["Data"] != null)
{
Search.Visible = false;
pnlSearchResult.Visible = true;
}
}

I recommend solution without using Response.Redirect.
Code Behind Submit Button click:
protected void btnSubmit_Click(object sender, EventArgs e)
{
if (IsValid)
{
pnlSearch.Visible = false;
pnlSearchResult.Visible = true;
}
}
In Markup:
<asp:Panel ID="pnlSearchResult" runat="server" Visible="false">
<script>
var searchTxt = document.getElementById('search');
if(searchTxt.value != null && searchTxt.value != ''){
//do your stuff
}
</script>

Adding Dynamic Controls in ASP.NET

It kind of seems to me that there is an inherent difficulty in dynamically adding controls in ASP.NET Web Forms. Specifically, for a dynamically added control to be included in the ViewState, and have it's events properly wired up and so forth it is suggested that these be added during the Page_PreInit event.
That said, many times we'll probably want to add such controls according to an event, such as a user clicking a button. Control specific events like Click events always run after Init, and even after Load. Supposed the following .aspx....
<form id="form1" runat="server">
<div>
<asp:PlaceHolder ID="phAddresses" runat="server"></asp:PlaceHolder>
<br /><br />
<asp:Button ID="btnAddAddress" runat="server" Text="Add Another Address" OnClick="btnAddAddress_Click" />
...and the following .aspx.cs....
private static List<AddressUserControl> addresses = new List<AddressUserControl>();
protected void Page_PreInit(object sender, EventArgs e)
{
foreach (AddressUserControl aCntrl in addresses)
{
phAddresses.Controls.Add(aCntrl);
// Helper to find button within user control
addressButtonControl = findAddressControlRemoveButton(aCntrl);
addressUserControlButton.ID = "btnRemoveAddress" + addressCount;
addressUserControlButton.Click += new EventHandler(addressUserControlButton_Click);
addressCount++;
}
}
protected void btnAddAddress_Click(object sender, EventArgs e)
{
AddressUserControl aCntrl = LoadControl("~/UserControls/AddressUserControl.ascx") as AddressUserControl;
addresses.Add(aCntrl);
}
Now in the above situation the number of User Controls displayed is always one behind the number the user has actually added, because the Click event doesn't run until after PreInit, where controls must be added to the placeholder. I must be missing something here, because this seems inherent to the ASP lifecycle, and to require some 'hack' or other.
EDIT - Yeah for some reason EventHandlers I add during btnAddress_Click() won't run, only EventHandlers I add during Page_Init, or declaratively in markup. This is what I tried to do...
protected void btnAddAddress_Click(object sender, EventArgs e)
{
AddressUserControl aCntrl = LoadControl("~/UserControls/AddressUserControl.ascx") as AddressUserControl;
addresses.Add(aCntrl);
phAddresses.Controls.Add(aCntrl);
findAddressControlRemoveButton(aCntrl);
addressUserControlButton.ID = "btnRemoveAddress" + addresses.Count;
///////////////////////////////////////////////////////////////////////////////////
// ADDED EVENT HANDLER HERE
//////////////////////////////////////////////////////////////////////////////////////
addressUserControlButton.Click += new E ventHandler(addressUserControlButton_Click);
}
...but the event won't fire as I've said. Any ideas?
EDIT - Here's the markup for my AddressUserControl. There's no logic in the code behind file
<%# Control Language="C#" ClassName="AddressUserControl" AutoEventWireup="true" CodeBehind="AddressUserControl.ascx.cs" Inherits="XFAWithUserControl.UserControls.AddressUserControl" %>
<asp:Panel ID="pnlAddressForm" runat="server">
<asp:Label ID="lblStreet" runat="server" Text="Street Address"></asp:Label>
<asp:TextBox ID="txtStreet" runat="server"></asp:TextBox>
<br /><br />
<asp:Label ID="lblCity" runat="server" Text="City"></asp:Label>
<asp:TextBox ID="txtCity" runat="server"></asp:TextBox>
<br /><br />
<asp:Label ID="lblState" runat="server" Text="State"></asp:Label>
<asp:TextBox ID="txtState" runat="server"></asp:TextBox>
<br /><br />
<asp:Label ID="lblZip" runat="server" Text="Zip"></asp:Label>
<asp:TextBox ID="txtZip" runat="server"></asp:TextBox>
<br /><br />
<asp:Button ID="btnRemoveAddress" runat="server" Text="Remove Address" />
</asp:Panel>
right now my click event for btnRemoveAddress is just something silly like this...
private void addressUserControlButton_Click(object sender, EventArgs e)
{
Button thisButton = sender as Button;
thisButton.Text = "Why Hello";
}
but my goal is to have it remove the associated AddressUserControl, so that a user can add and/or remove an arbitrary number of AddressUserControls from the page by clicking buttons.
EDIT - Here's what I have now, still doesn't work
protected void btnAddAddress_Click(object sender, EventArgs e)
{
AddressUserControl aCntrl = LoadControl("~/UserControls/AddressUserControl.ascx") as AddressUserControl;
addresses.Add(aCntrl);
phAddresses.Controls.Add(aCntrl);
findAddressControlRemoveButton(aCntrl);
addressUserControlButton.ID = "btnRemoveAddress" + addresses.Count;
aCntrl.ChangeText += new EventHandler(addressUserControlButton_Click);
}
private void addressUserControlButton_Click(object sender, EventArgs e)
{
Button thisButton = sender as Button;
thisButton.Text = "Why Hello";
}
AddressUserControl.ascx
<asp:Panel ID="pnlAddressForm" runat="server">
<asp:Label ID="lblStreet" runat="server" Text="Street Address"></asp:Label>
<asp:TextBox ID="txtStreet" runat="server"></asp:TextBox>
<br /><br />
<asp:Label ID="lblCity" runat="server" Text="City"></asp:Label>
<asp:TextBox ID="txtCity" runat="server"></asp:TextBox>
<br /><br />
<asp:Label ID="lblState" runat="server" Text="State"></asp:Label>
<asp:TextBox ID="txtState" runat="server"></asp:TextBox>
<br /><br />
<asp:Label ID="lblZip" runat="server" Text="Zip"></asp:Label>
<asp:TextBox ID="txtZip" runat="server"></asp:TextBox>
<br /><br />
<asp:Button ID="btnRemoveAddress" runat="server" Text="Remove Address" OnClick="btnRemoveAddress_Click" />
</asp:Panel>
AddressUserControl.ascx.cs
public event EventHandler ChangeText;
protected void Page_Load(object sender, EventArgs e)
{
}
public void btnRemoveAddress_Click(object sender, EventArgs e)
{
if (this.ChangeText != null)
{
ChangeText(sender, e);
}
}

You need to have the logic in your click handler add to the panel's Controls collection as well as to the list of controls, like this:
protected void btnAddAddress_Click(object sender, EventArgs e)
{
AddressUserControl aCntrl = LoadControl("~/UserControls/AddressUserControl.ascx") as AddressUserControl;
addresses.Add(aCntrl);
phAddresses.Controls.Add(aCntrl);
}
UPDATE:
In your user control, you need to define an event that can be defined in the page that hosts the user control, like this:
AddressUserControl.cs (code-behind):
public event EventHandler RemoveAddress;
protected void removeAddressUserControlButton_Click(object sender, EventArgs e)
{
// Find out if the event has been set, if so then call it
if (this.RemoveAddress!= null)
{
RemoveAddress(sender, e);
}
}
Now on your page where you are using the user control, do this:
// Wire up the user control's event
nameOfUserControl.RemoveAddress += new EventHandler(addressUserControlButton_Click);
Finally, implement the addressUserControlButton_Click event:
protected void addressUserControlButton_Click(object sender, EventArgs e)
{
// Do your dynamic control creation here or whatever else you want on the page
}