I have a simple ASP.NET page with a button and a textbox, I want to click the button and have "Hello" appear in the textbox.
<%# Page Language="C#" AutoEventWireup="true" CodeFile="SOM.aspx.cs" Inherits="SOM" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div><br />
</div>
<asp:Button ID="MyBtn" runat="server" Text="Click" OnClick="SearchBtn_Click" />
<br />
<br />
<asp:TextBox ID="TextBox1" runat="server" Width="268px"></asp:TextBox>
in the code behind I am able to use Intellisence to autocomplete TextBox1.Text = "Hello";
but then when I try to debug, the project fails to build saying
The name TextBox1 does not exist in the current context
Is there a property that I need to set?
///Code behind
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Windows.Input;
public partial class SOM: System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void SearchBtn_Click(object sender, EventArgs e)
{
//TextBox1.Text = "HI";
}
protected void TextBox1_TextChanged(object sender, EventArgs e)
{
}
}
If any of the great answers here do not work, here's another solution that once caused me a few gray hairs, especially if you're using VS 2012.
If your project is a web application, delete the designer.cs file. Then right click on the aspx file and select "Convert to Web Application".
For as great as Visual Studio is, sometimes these stupid WTF things drive me absolutely nuts.
Your aspx page is not referencing the correct code behind.
In the head of your aspx page replace with
<%# Page Language="C#" AutoEventWireup="true" CodeFile="myName.aspx.cs" Inherits="myName" %>
That should work
NOTE: I now know this isn't the problem, I but updated my answer in case it solves someone else's problem.
If you are using a namespace somewhere between your codebehind or the aspx page, you have to make it consistent.
I will use "MyProject" as a sample namespace.
namespace MyProject
{
public partial class SOM: System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void SearchBtn_Click(object sender, EventArgs e)
{
TextBox1.Text = "HI";
}
protected void TextBox1_TextChanged(object sender, EventArgs e)
{
}
}
}
In your aspx page, change Inherits="SOM" to Inherits="MyProject.SOM".
Related
I am very new to ASP.NET but I have background in C and C#. I am trying to make web application which will be connected with my database. I did that and that is OK. The problem occurred when I added buttons for moving forward and backward through the database... It was working fine but only for one click! Then I thought that probably I have bug in the code and I decided to do it in easy way.
I created new web form with just one button and one label, but behavior is still the same- after first click event is not fired again. Any help?
My code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace DummyTest
{
public partial class WebForm1 : System.Web.UI.Page
{
int pom = 0;
protected void Page_Load(object sender, EventArgs e)
{
Label1.Text = Convert.ToString(pom);
}
protected void Button1_Click(object sender, EventArgs e)
{
pom++;
Label1.Text = Convert.ToString(pom);
}
}
}
and source
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs"
Inherits="DummyTest.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
Dummy Test
<br />
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button" />
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<br />
</div>
</form>
</body>
Your Webform class gets recreated on every request - that's just how it works. You need to persist the field pom in some other way. You could add it to the session state, but that affects scalability of the application as you then hold state on the server.
It is already persisted by the label control, so you could do something like this in your click event:
var pom = Int.Parse(Label1.Text);
pom++;
Label1.Text = pom.ToString();
However, this will not always be the case for something you want to persist. In these cases I would add a hidden field to the html which holds it. My WebForms is a little rusty, but in your markup:
<asp:HiddenField id="pom" value="0" />
then pull the value out and increment in the click event as I've done above.
Whenever you click your int pom = 0 get initialized to zero and then you set value that is why it looks it calling once. either make it static or better to try:
protected void Button1_Click(object sender, EventArgs e)
{
Label1.Text = "" + (Convert.ToInt32(Label1.Text) + 1);
}
You could try moving your initialisation into an IsPostBack check, so reloading the page does not re-intitialise the variable to 0. The IsPostBack value indicates whether the page is being rendered for the first time or is being loaded in response to a postback and a button click event triggers a postback.
Additional
The IsPostBack fires at a specific stage in the page lifecycle
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
int pom = 0;
}
Label1.Text = Convert.ToString(pom);
}
To some extent it depends what the purpose of the pom variable is. If it is tracking clicks per user then the above should help. However if you're tracking clicks across all users then you should consider something else (probably using the global.asax)
It is working now! Here is code for Up and Down.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace DummyTest
{
public partial class WebForm1 : System.Web.UI.Page
{
static int pom;
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == false)
{
pom = 0;
Label1.Text = Convert.ToString(pom);
}
}
protected void Button1_Click(object sender, EventArgs e)
{
var pom = Int32.Parse(Label1.Text);
pom++;
Label1.Text = Convert.ToString(pom);
}
protected void Button2_Click(object sender, EventArgs e)
{
var pom = Int32.Parse(Label1.Text);
pom--;
Label1.Text = Convert.ToString(pom);
}
}
}
I'm using VisualStudio 2013 Express for WEB, and I created an empty web application, and then added a new web form.
I'm trying to learn ASP.NET, and I learned that in the session / page life cycle there is Page_Load where I can execute thing that will happen just after the page loads. The thing is I learned that it is possible to put the Page_Load event under <script> before the <HTML> tag.
(The aspx file name is Register) When I try this:
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="Register.aspx.cs" Inherits="Learning.Register" %>
<!DOCTYPE html>
<script runat="server">
int randomnumber = 0;
public void Page_Load()
{
Random rnd = new Random();
randomnumber = rnd.Next(100000, 1000000);
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<% Response.Write(randomnumber); %>
</div>
</form>
</body>
</html>
All I get is 0 for some reason.
Also, I noticed that under Register.aspx.cs I have this:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace Learning
{
public partial class Register : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
}
}
You can definitely put the server side code in aspx using script tag. But the page load syntax should exactly match as it is in your code behind(.cs file)
Page_Load(object sender, EventArgs e)
In your script code you have just Page_Load() which does not trigger at all.
If you need this to be excecuted then you need to remove the function in the code behind and replace the method signature in the script tag
in the script tag you need to have base.OnLoad(e)
protected void Page_Load(object sender, EventArgs e)
{
base.OnLoad(e)
Random rnd = new Random();
randomnumber = rnd.Next(100000, 1000000);
}
That's because you are overriding the behavior of the base class, and if you don't call base.OnLoad(e) then Page_Load would not run in the markup side.
Here is all my code:
Site.Master
<%# Master Language="C#" AutoEventWireup="true"
CodeBehind="Site.master.cs" Inherits="WebApplication1.SiteMaster" %>
<!DOCTYPE html>
<html>
<head runat="server">
<title></title>
<link href="~/Styles/Site.css" rel="stylesheet" type="text/css" />
<asp:ContentPlaceHolder ID="HeadContent" runat="server">
</asp:ContentPlaceHolder>
</head>
<body>
<form runat="server">
<div class="main">
<asp:ContentPlaceHolder ID="MainContent" runat="server"/>
</div>
</form>
</body>
</html>
Site.Master.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebApplication1
{
public partial class SiteMaster : System.Web.UI.MasterPage
{
protected void Page_Load(object sender, EventArgs e)
{
}
}
}
Default.aspx
<%# Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master"
AutoEventWireup="true" CodeBehind="Default.aspx.cs"
Inherits="WebApplication1._Default" %>
<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
<asp:ListBox ID="ListBox1" runat="server"></asp:ListBox>
</asp:Content>
Default.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebApplication1
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
ListBox ListBox1 = new ListBox();
ListBox1.FindControl("ListBox1");
ListBox1.Items.Add(new ListItem("Hello"));
}
}
}
Question: Why is my ListBox not populating?
When running the code I get a page with a small box that is completely empty.
I tried the following already and I will tell you the result -
Remove
ListBox ListBox1 = new ListBox();
ListBox1.FindControl("ListBox1");
Result: The name 'ListBox1' does not exist in the current context
Add a reference to ListBox1 manually into the designer.
Result: Object reference not set to an instance of an object.
To fix that error adding the line ListBox ListBox1 = new ListBox(); works, but still does not display.
Any ideas? Thanks.
You should only need...
protected void Page_Load(object sender, EventArgs e)
{
ListBox1.Items.Add(new ListItem("Hello", "H"));
}
See this link too
EDIT: Same code works for me.
To directly answer your question of why ListBox1 isn't getting populated:
protected void Page_Load(object sender, EventArgs e)
{
ListBox ListBox1 = new ListBox(); //You are creating a new local ListBox named ListBox1.
ListBox1.FindControl("ListBox1"); //You are trying to find the Control named ListBox1 that is held within the Control ListBox1 (and not doing anything with the result of the search)
ListBox1.Items.Add(new ListItem("Hello")); //You are adding a new ListItem to the local ListBox1.
}
As christiandev said, you should just be able to do this:
protected void Page_Load(object sender, EventArgs e)
{
ListBox1.Items.Add(new ListItem("Hello"));
}
I have no idea why you can't seem to access the ListBox1 on the aspx page.
I am using FileUpload Control to upload images, I can select the image using that browse button, but when i try to preview that selected one, i am not getting the file name, its showing empty..
protected void btnImgUpload_Click(object sender, ImageClickEventArgs e)
{
try
{
string strimage;
string strfilename, strextn;
if (fupImage.HasFile)
{
In the above code,fupImage.FileName property should have to selected Image name, but it remains as empty string "" , so fubImage.HasFile condition is going false. I am not getting why the condition is going false, while the file is selected,? what is the problem here?
Thanks in advance
what i did to test it is
I create an Asp page
<%# Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication2.WebForm1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:FileUpload ID="fupImage" runat="server" />
<asp:Button ID="btnImageUpload" runat="server" onclick="btnImageUpload_Click"
Text="Upload" />
</div>
</form>
</body>
</html>
and the code behind class is
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebApplication2
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnImageUpload_Click(object sender, EventArgs e)
{
try
{
string strimage;
string strfilename, strextn;
if (fupImage.HasFile)
{
//do something
}
}
catch
{
}
}
}
}
and nothing goes wrong with that
I want to say to test it just create a very simple instance and test it in complex environment may be there are some extra rules may prevents normal jobs! and sometimes it looks so unnoraml
Check for the View-state property of that file uploader Control, If View-state is false, then on post back you'll get empty value
I have a number of pages that I need to Dynamically Load User Controls and process events on controls on them. I have included sample code below for a trivial example.
Default.aspx
<%# Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Button ID="BtnLoadControl" runat="server" Text="Load Control 1"
onclick="BtnLoadControl_Click" /><br />
<asp:Button ID="BntLoadControl2" runat="server" Text="Load Control 2"
onclick="BntLoadControl2_Click" />
<asp:PlaceHolder ID="ControlArea" runat="server" />
</div>
</form>
</body>
</html>
Deafualt.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void BtnLoadControl_Click(object sender, EventArgs e)
{
Control controlToAdd = Page.LoadControl("~/control1.ascx");
this.ControlArea.Controls.Add(controlToAdd);
}
protected void BntLoadControl2_Click(object sender, EventArgs e)
{
Control controlToAdd = Page.LoadControl("~/control2.ascx");
this.ControlArea.Controls.Add(controlToAdd);
}
}
Control1.ascx
<%# Control Language="C#" AutoEventWireup="true" CodeFile="control1.ascx.cs" Inherits="control1" %>
<div style="border: 1px solid red;">Test Control
<br /><asp:Button runat="server" ID="testButton" Text="test" onclick="testButton_Click" /></div>
Control1.ascx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class control1 : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void testButton_Click(object sender, EventArgs e)
{
Response.Write("Button Clicked on Control 1!");
}
}
Control2.ascx
<%# Control Language="C#" AutoEventWireup="true" CodeFile="Control2.ascx.cs" Inherits="Control2" %>
<div style="border: 1px solid red;">Test Control 2
<br /><asp:Button runat="server" ID="testButton2" Text="test me"
onclick="testButton2_Click" /></div>
Control2.ascx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class Control2 : System.Web.UI.UserControl
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void testButton2_Click(object sender, EventArgs e)
{
Response.Write("Button Clicked on Control 2!");
}
}
This is a very trivial example to show what I would like to do. My actual control is more complex and has several properties that I set for the control I load as I load it (in the default.aspx.cs files event handler).
With this example what happens is when the button is clicked on one of the loaded controls, the page is re-loaded and the control is no longer there. How can I keep the control loaded as well as process any events that happen on the control?
You're asking if you can keep the control loaded in the page?
You can't keep the control loaded in the page, because the page doesn't exist! It's recreated on every request. It's created from the markup (compiled or not), and from running any code in the CodeBehind. If you want your controls to be there after a PostBack, then you need to recreate them on the PostBack. If you want to process events on those controls, then you'll have to wire the controls to event handlers when you recreate them after PostBack. Then the events will fire.