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FindControl() always returns null from DataList Textbox

I have 8 items in a SQL table with a Description, ItemNumber, and ImagePath.
protected void Page_Load(object sender, EventArgs e)
{
//fill the datalist for the Signs Table
string tCallFrom = "Program." + System.Reflection.MethodBase.GetCurrentMethod().Name;
string tQry = #"SELECT * FROM [js_Signs]";
DataTable tblSigns = objCommMethods.fReturnTableFromQry(clsDBSelect.enumDBSelect.ProjectMaster, tQry, tCallFrom);
SignsList.DataSource = tblSigns;
SignsList.DataBind();
}
I am using a DataList to show all of the items along with a textbox that will allow a user to input the number of items they want:
<asp:DataList ID="SignsList" runat="server" RepeatColumns="4" CellPadding="2" Width="90%" ItemStyle-HorizontalAlign="Center">
<ItemTemplate>
<table>
<tr>
<th>
<%#DataBinder.Eval(Container.DataItem, "Description") %>
</th>
</tr>
<tr>
<th>
<%#DataBinder.Eval(Container.DataItem, "ItemNumber") %>
</th>
</tr>
<tr>
<td>
<asp:Image ID="SignImage" runat="server" ImageUrl='<%#DataBinder.Eval(Container.DataItem, "ImagePath") %>' />
</td>
</tr>
<tr style="text-align: center;">
<td>
<asp:TextBox ID="txtSignQuantity" runat="server" CssClass="txtBox" BackColor="White" Enabled="true"
type="number" min="0" ToolTip="Please choose quantity of signs needed."/>
</td>
</tr>
<tr>
<td>
<p> </p>
</td>
</tr>
</table>
</ItemTemplate>
</asp:DataList>
<div class="btnGroup">
<div class="btnDiv">
<asp:Button ID="btnSave" runat="server" Text="Save" CssClass="btnSave" Width="90px" Visible="true" OnClick="btnSave_Click"/>
</div>
<div class="btnDiv">
<asp:Button ID="btnCancel" runat="server" Text="Clear" CssClass="btnCancel" Width="90px" Visible="true" OnClick="btnCancel_Click"/>
</div>
</div>
After the saved button is clicked in C# I want to find out the value that a user entered but it is always returning null:
protected void btnSave_Click(object sender, EventArgs e)
{
TextBox txtSignQuantity;
string tempSignQuantity;
try
{
foreach (DataListItem item in SignsList.Items)
{
txtSignQuantity = item.FindControl("txtSignQuantity") as TextBox;
tempSignQuantity = txtSignQuantity.Text;
}
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
I also checked and the Count of SignsList.Items was 8, so I know that it is retrieving the correct information. Sorry, I've never used a Data List before so I'm not really sure how to go about this...

The short answer is that data binding on postback is causing the problem. Check the Page.IsPostBack property before doing data binding:
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
//fill the datalist for the Signs Table
string tCallFrom = "Program." + System.Reflection.MethodBase.GetCurrentMethod().Name;
string tQry = #"SELECT * FROM [js_Signs]";
DataTable tblSigns = objCommMethods.fReturnTableFromQry(clsDBSelect.enumDBSelect.ProjectMaster, tQry, tCallFrom);
SignsList.DataSource = tblSigns;
SignsList.DataBind();
}
}
ASP.NET WebForms attempts to abstract away the fact that the control instances that were used to render the page are not the same instances it has when handling postback events. Data binding compounds the abstraction because it has to create controls in response to the DataBind call, and then on postback, recreate them based on the ViewState it saved.
Initializing controls from ViewState happens on the Init event, so when the Load event is fired later in the page lifecycle and you call DataBind on the control, everything it restored gets wiped out and recreated.
As for why you were getting null, it may have been that the controls were wiped out but not recreated; it may have had to do with other event handlers that didn't get rewired after the second data binding.

How to get individual error labels to show C# asp.net

I am working on a contact page and would like some help please on how to display error labels at individual times when the textboxes are empty. I have used 3 textboxes. I am a new student in C# asp.net. I really appreciate your time and help. Thanks!
//if no or incorrect entries are entered panel with red message using a label appears to remind the user of
//if name, email, enquiry is blank error labels show up
if (nameContactUsTextBox.Text == "" && emailContactUsTextBox.Text == "" && enquiryContactUsTextBox.Text == "")
{
nameErrorLabel.Visible = true;
emailErrorLabel.Visible = true;
equiryErrorLabel.Visible = true;
}
if (nameContactUsTextBox.Text != "" && emailContactUsTextBox.Text == "" && enquiryContactUsTextBox.Text == "")
{
emailErrorLabel.Visible = true;
equiryErrorLabel.Visible = true;
}
if (nameContactUsTextBox.Text == "" && emailContactUsTextBox.Text != "" && enquiryContactUsTextBox.Text == "")
{
nameErrorLabel.Visible = true;
equiryErrorLabel.Visible = true;
}
if (nameContactUsTextBox.Text == "" && emailContactUsTextBox.Text == "" && enquiryContactUsTextBox.Text != "")
{
nameErrorLabel.Visible = true;
emailErrorLabel.Visible = true;
}
aspx file
<p>
<table style="width: 100%;">
<tr>
<td class="boring">Name</td>
<td class="auto-style1">
<asp:TextBox ID="nameContactUsTextBox" runat="server" CssClass="boring" ToolTip="Enter Name" Width="441px"></asp:TextBox>
<asp:Label ID="nameErrorLabel" runat="server" CssClass="redalert" Text="*complete name" Visible="False"></asp:Label>
</td>
</tr>
<tr>
<td class="boring">E-Mail</td>
<td>
<asp:TextBox ID="emailContactUsTextBox" runat="server" CssClass="boring" ToolTip="Enter Email" Width="443px"></asp:TextBox>
<asp:Label ID="emailErrorLabel" runat="server" CssClass="redalert" Text="*complete email" Visible="False"></asp:Label>
</td>
</tr>
<tr>
<td class="boring">Enquiry</td>
<td class="auto-style5">
<asp:TextBox ID="enquiryContactUsTextBox" runat="server" CssClass="classic" Height="158px" ToolTip="Enter Enquiry" Width="441px"></asp:TextBox>
<asp:Label ID="equiryErrorLabel" runat="server" CssClass="redalert" Text="*complete enquiry" Visible="False"></asp:Label>
</td>
</tr>
<tr>
<td class="auto-style5"></td>
<td class="auto-style2"></td>
</tr>
<tr>
<td class="smallheader" colspan="2"> </td>
</tr>
<tr>
<td class="auto-style5"> </td>
<td class="auto-style2"> </td>
</tr>
<tr>
<td class="auto-style5" colspan="2">
<asp:Button ID="sendButton" runat="server" CssClass="smallheader" OnClick="sendButton_Click" Text="Send" ToolTip="Sending to NeoMan!" Width="200px" />
<asp:Button ID="homeButton" runat="server" CssClass="smallheader" OnClick="homeButton_Click" Text="Home" ToolTip="Continue Shopping With NeoMan" Width="200px" />
<asp:Button ID="resetButton" runat="server" CssClass="smallheader" OnClick="resetButton_Click" Text="Reset Form" ToolTip="Clear Form" Width="200px" />
</td>
</tr>
<tr>

You could use the TextChangedEvent like so:
protected void nameContactUsTextBox_TextChanged(object sender, EventArgs e)
{
nameErrorLabel.Visible = nameContactUsTextBox.Text == "";
}
And add the textchanged-event for each of the textboxes.

Microsoft already have buil ib validators that you can use to do this sort of task. To make sure that the field is not empty use the Required Field validator see this example on the w3c school website http://www.w3schools.com/aspnet/showaspx.asp?filename=demo_reqfieldvalidator.
For more complex validation use can use the regular expression validator. check the msdn website(http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.regularexpressionvalidator%28v=vs.110%29.aspx) for this it quite straight forward.
you can also investigate the JQuery validator it is quite flexible to do more interesting validation.

That's because you need to hide labels when they're not supposed to be shown, not only hide it. Change ifs to if-elses and add a summary else condition
else
{
nameErrorLabel.Visible = false;
emailErrorLabel.Visible = false;
equiryErrorLabel.Visible = false;
}

You should use the
placeholder
property of the textbox to display the type of value you need entered and examine those answers with jquery either after the boxes lose focus or upon a click of a button. If you need some sample code let me know

Text box getting cleared because of update panel

I've have one table, in that table within one I've one and within that , I've update panel whose update mode is set to conditional. Within this update panel I've another table. The table contains 3 text boxes as: old password, new password and confirm password. On the textChanged event of the old password I am checking the user entered value with the value in db. But when the function completes its execution all the 3 text boxes looses its values regardless of whether I update the update panel or not. I don't know why it clears text boxes. I want to prevent text boxes from getting cleared. I tried to get the text box text in string variable and again assign it to text boxes (both in text box text changed event and in page load event under isPostBack condition) but its too, not working.
asp code:
.
.
.
<tr>
<td colspan="3">
<div>
<asp:UpdatePanel ID="updPnlChngPwd" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<table style="width:100%">
<tr>
<td>
Old Password
</td>
<td>:</td>
<td>
<asp:TextBox ID="txtOldPwd" runat="server" Height="21px" MaxLength="50" TextMode="Password" Width="60%" ontextchanged="txtOldPwd_TextChanged"
AutoPostBack="True"></asp:TextBox>
</td>
</tr>
<tr>
<td></td>
<td></td>
<td>
<asp:Label ID="lblWrongOldPwd" runat="server" Text="Wrong Old Password" ForeColor="Red" Visible="False"></asp:Label>
</td>
</tr>
<tr>
<td>
Password
</td>
<td>:</td>
<td></td>
</tr>
<tr>
<td></td>
<td>:</td>
<td>
<asp:TextBox ID="txtSuppRePwd" runat="server" Height="21px" MaxLength="50" TextMode="Password" Width="60%"></asp:TextBox>
</td>
</tr>
<tr>
<td></td>
<td>
<asp:Button ID="btnUpdPwd" runat="server" Text="Change Password" onclick="btnUpdPwd_Click"/></td>
<td>
</td>
</tr>
</table>
</ContentTemplate>
</asp:UpdatePanel>
</div>
<td>
</tr>
.
.
.
C# code for tetxt box textChanged event:
protected void txtOldPwd_TextChanged(object sender, EventArgs e)
{
DataTable dtOldPwd = Obj.DBAccess("select Pwd from Customer where Cust_Id = " + Convert.ToInt32(Session["SuppID"]) + " and Supp_Pwd = '" + txtOldPwd.Text + "'");
if (dtOldPwd.Rows.Count == 1)
{
lblWrongOldPwd.Visible = false;
}
else
{
lblWrongOldPwd.Visible = true;
updPnlChngPwd.Update();
}
}
Now I am not able to understand what exactly wrong I am doing, does having update panel inside the table causing problem?

<td>
<asp:TextBox ID="txtSuppRePwd" runat="server" Height="21px" MaxLength="50" TextMode="Password" Width="60%"></asp:TextBox>
</td>
You have TextMode set to password which will not save your textbox value .
However you will get your textbox value as string on textchange event
protected void txtbx_TextChanged(object sender, EventArgs e)
{
string txtValue = txtbx.Text;
ViewState["xyz"]= txtValue;
}
and you have to save this value in ViewState to use it for btnClick event .
OR
You can also set textbox attribute at Page_Load event which is a very bad practice to do like this
protected void Page_Load(object sender, EventArgs e)
{
txtbx.Attributes.Add("value", txtbx.Text);

TextBox with TextMode="Password" will be cleared after postback or partial postback. This is the default behavior of the password textbox so submit all the data at a time and do the validation in your code.
Alternatively, You can store password in in viewstate or session and restore after postback.

Retrieving value from Asp.Net TextBox

Problem: I have an asp.net Textbox that I am putting text into and on text change it should assign its value to a variable, this does not happens.
Question: What is the best method to retrieve the value from the Textbox?
C# Code:
protected void btnSourceConnect_Click(object sender, EventArgs e)
{
if (Util.Connection(SourceString, 0))
{
lblTesting.Text = "Working!";
}
else
{
lblTesting.Text = "It No Work";
}
}
protected void txtSourceServer_TextChanged(object sender, EventArgs e)
{
SourceString.DataSource = txtSourceServer.Text;
}
protected void txtSourceDatabase_TextChanged(object sender, EventArgs e)
{
SourceString.InitialCatalog = txtSourceDatabase.Text;
}
protected void txtSourceUN_TextChanged(object sender, EventArgs e)
{
SourceString.UserID = txtSourceUN.Text;
}
protected void txtSourcePass_TextChanged(object sender, EventArgs e)
{
SourceString.Password = txtSourcePass.Text;
}
Asp.Net Code:
<table style="width: 100%;Border:1px solid Black;">
<tr>
<td class="style1">
Source Server:</td>
<td class="style1">
<asp:TextBox ID="txtSourceServer" runat="server"
ontextchanged="txtSourceServer_TextChanged" AutoPostBack="True"></asp:TextBox>
</td>
<td class="style1">
Source Database:
</td>
<td class="style1">
<asp:TextBox ID="txtSourceDatabase" runat="server"
ontextchanged="txtSourceDatabase_TextChanged" AutoPostBack="True"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style1">
User Name:
</td>
<td class="style1">
<asp:TextBox ID="txtSourceUN" runat="server"
ontextchanged="txtSourceUN_TextChanged" AutoPostBack="True"></asp:TextBox>
</td>
<td class="style1">
Password:
</td>
<td class="style1">
<asp:TextBox ID="txtSourcePass" runat="server"
ontextchanged="txtSourcePass_TextChanged" AutoPostBack="True"></asp:TextBox>
</td>
</tr>
<tr>
<td class="style1">
</td>
<td class="style1">
</td>
<td class="style1">
</td>
<td class="style1">
<asp:Button ID="btnSourceConnect" runat="server" Text="Test Connection"
onclick="btnSourceConnect_Click" />
</td>
</tr>
</table>

What is the best method to retrieve the value from the Textbox?
The best method is like this control I am writing right now, you have a button that make post back, and then you read the value of the text box on code behind - on post back.
Using the AutoPostBack="True" on every TextBox you use involves too many unnecessary post backs to the server, it is better to use a "submit" button and save all your values when the user click on submit.
In you case you have a button, and you only need to remove the auto post back and set your values only when you try to connect as:
protected void btnSourceConnect_Click(object sender, EventArgs e)
{
SourceString.UserID = txtSourceUN.Text;
SourceString.DataSource = txtSourceServer.Text;
SourceString.InitialCatalog = txtSourceDatabase.Text;
SourceString.Password = txtSourcePass.Text;
if (Util.Connection(SourceString, 0))
{
lblTesting.Text = "Working!";
}
else
{
lblTesting.Text = "It No Work";
}
}

AutoPostback = true on a TextBox will cause the page to post back when the text box loses focus, not on every text change.
From the look of your code most of this functionality should be happening on the client side (i.e. with javascript).

Want Checked Item From Listview

I am working with listview in C# webapplication. My Problem is I want checked Items from the listview . I have try with find selecteditem and all. I dont know how to get checked items from checkbox inside listview.My code is as follows:-
aspx
<asp:ListView ID="PackagesListView" runat="server" DataSourceID="PackagesDataSource" ItemPlaceholderID="itemPlaceholder"
GroupItemCount="4" GroupPlaceholderID="groupPlaceholder" OnItemDataBound="PackagesListView_ItemDataBound">
<LayoutTemplate>
<table style="margin-left:0px; width:570; table-layout:fixed; overflow:hidden;">
<tr ID="groupPlaceholder" runat="server" >
</tr>
</table>
</LayoutTemplate>
<GroupTemplate>
<tr class="productsTableRow">
<td ID="itemPlaceholder" runat="server"></td>
</tr>
</GroupTemplate>
<ItemTemplate>
<td style="width:140px;">
<div style="text-align:center; line-height:1.5;"><asp:Label ID="PackageLabel" runat="server" Text='<%#Eval("Name")%>' /></div>
<div style="text-align:center;"><asp:CheckBox ID="PackageCheckBox" runat="server" OnCheckedChanged="OnPackageSelected" AutoPostBack="true" PackageID='<%#Eval("PackageID")%>' /></div>
</td>
</ItemTemplate>
</asp:ListView>
<asp:Button ID="ButtonSaveQuotation" runat="server" Text="Save Quotation"
CssClass="button" Visible="false" onclick="ButtonSaveQuotation_Click1" />
aspx.cs
protected void ButtonSaveQuotation_Click1(object sender, EventArgs e)
{
StringBuilder sb = new StringBuilder();
}
so here in sb I want to append text of all the label whose checkboxes are checked.Thank You

You will have to find the checkbox since it's inside the template field
Example:
if (PackagesListView.Items.Count > 0)
{
for (int i = 0; i < PackagesListView.Items.Count; i++)
{
CheckBox PackageCheckBox= (CheckBox)PackagesListView.Items[i].FindControl("PackageCheckBox");
if (PackageCheckBox!= null)
{
if (PackageCheckBox.Checked.Equals(true))
{
//do your stuff here
}
}
}
}

foreach (var item in PackagesListView.Items.Where(i => ((CheckBox)i.FindControl("PackageCheckBox")).Checked))
{
var label =(Label) item.FindControl("PackageLabel");
label.Text += " Appended text";
}
Perhaps this will help you? This should go after page load. Also make sure you are not rebinding your listview.

var texts = PackagesListView.Items.Cast<Control>()
.Where(c => ((CheckBox)c.FindControl("PackageCheckBox")).Checked)
.Select(c => ((Label)c.FindControl("PackageLabel")).Text);
var sb = new StringBuilder();
foreach ( var text in texts)
sb.AppendLine(text);