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access local storge with javascript and C#, asp.net

i am hoping someone will help me, i am pulling out my hair for the last few hours...!
I am using asp.net web forms with c#
I have the following button in my menu , this button opens up a page that lists selected properties for realtor…
htmlCode.Append("<button type='button' class='btn btn-basic' id='btnEnquire' onclick='openEnquiryPage()'> <span class='glyphicon glyphicon-th-list'></span> View my list </button>");
function openEnquiryPage() {
location.href = "EnquiryPage.aspx";
//get the list from the storage into the hidden field
//getListOfProperties();//not in use...
}
The list is stored in localstorage as Json, I can see the correct data in the text box on the page
var retrievedData = localStorage.getItem("propertyArray");
proplist2.value = retrievedData;
declared as follows in asp.net control
<asp:TextBox ID="TextBox1" runat="server" Text="initial"></asp:TextBox>
BUT in the hidden field, the data is always = ""
<asp:HiddenField ID="txtPropList" runat="server"></asp:HiddenField>
javascript to populate the hidden field...
function getListOfProperties() {
document.getElementById("body_content_txtPropList").value = retrievedData;
var proplist2 = document.getElementById("body_content_txtPropertyList");
proplist2.value = retrievedData;
}
when I debug the following lines in the code behind ...
Page.ClientScript.RegisterStartupScript(this.GetType(),"prop", "getListOfProperties();",true);
_propertyListJson = txtPropList.Value;
propertyListJson I always = “”
Thank-you in advance.!

If you want to use the hidden field then you should use
<%=txtPropList.ClientID%>
as on when you render the page and see it in inspect element server would render the different Id so it would not store the value in hidden field simply so it is feasible to use ClientID to create the static mode. But as on when you call the javascript function from the c# code then it would call the javascript function but it would not wait for it and execute the next line of code as on at that time the value is not store in hidden field so it would return the null value.
If you want then call the function of javascript on page load event and then click the button and retrieve the value it would successfully retrieve the value but i dont think that these would be the feasible code from my opinion
I suggest to create the WebAPI which would simply get the the data from the localstorage and perform the operation
And webAPI can be easily called from javascript using ajax call
I hope this would be helpful and answer is satisfactory 😊☺
Thank You ☺🙂

Unable to get value of input using ASP.NET

I'm trying to return some text which was inputted into a textbox element on my website. After entering some text into it I noticed that this didn't return data:
document.getElementById('myTextBox').text;
But this did:
document.getElementById('myTextBox').value;
EDIT: The javascript above was used client side to test what was being read, using .text returns an empty string which, when passed back to the server, did indeed show an empty string. .value contained my entered data but when I tried using .value server side the errors occurred.
However in my .cs class when I tried to add the following:
string myInput = myTextBox.Value;
I get an error message saying
"System.Web.UI.WebControls.TextBox doesn't contain a definition for
'Value'...".
The example I was referencing came from here: http://www.aspsnippets.com/Articles/Get-value-of-HTML-Input-TextBox-in-ASPNet-code-behind-using-C-and-VBNet.aspx
My textbox is declared like:
<asp:TextBox ID="myTextBox" runat="server"></asp:TextBox>
However when I try to change the TextBox element to an Input element I get an error saying "The type or namespace name 'Input' does not exist..."
How can I pass the data which was entered into my TextBox back to the server?

In the tutorial you are refering they have demonstared how to access the html input textbox value at server side. You are mixing a html control and a asp.net server control.
This represents a ASP.NET server control:-
<asp:TextBox ID="myTextBox" runat="server"></asp:TextBox>
and you can access its value at server side (.cs file) like this:-
string vaue = myTextBox.Text;
On the other hand the html input can be converted into a server control by adding the runat="server" attribute like this:-
<input type="text" id="txtName" name="Name" value="" />
In this case it is HtmlInputText and you need to access it value like this:-
string value = txtName.Value;

HTML elements e.g (input) are not accessible in your code behind. Asp.Net controls like the one you used can be accessed if you use the runat="server" attribute.
If you want to access yout Asp.Net textbox in your codebehind (.cs) you don't need javascript. Just use:
string value = this.myTextBox.Text
But, if you textbox is only a HTML input, than, you need to use some Javascript logic to get the value of the input and pass it to your .cs file.
For that, you have to do something like this:
Passing values from javascript to code behind in ASP.NET

Use:
string myInput = myTextBox.Text;
This give you all the text typed in the textbox

To get the text of your textbox for a javascript function :
function GetValueOfmyTextBox()
{
var myTB = document.getElementById('<%= myTextBox.ClientID %>');
alert(myTB.value);
}

How do I get text of label when changed to server side?

I'm trying to assign the text of a label to a hidden field when not post back but I fail. This is what I done.
If Not IsPostBack Then
Dim structPayperiod As strcPayperiodDet
structPayperiod = objTimeSystem.getCurrentPayPeriod()
hdnPayperiodseq.Value = structPayperiod.Payperiodid
hdnPayPeriodStartDt.Value = structPayperiod.startdate.ToString
lblPayPeriodStartDt.Text = structPayperiod.startdate
displayPayrollIdOrgs(objTimeSystem.getPayrollIDOrgs())
grd_Employees.Visible = False
RptErrorsMessages.DataSource = objTimeSystem.getErrorMessages()
RptErrorsMessages.DataBind()
Else
hdnPayPeriodStartDt.Value = lblPayPeriodStartDt.Text.ToString
End If
Problem comes in else clause where the value doesn't get update with new label value. lblPayPeriodStartDt.Text is not updating.
The value of label is date and it updates every time I change the date using calender control on client side. But, the value of the label doesn't refresh with that value.
<asp:Label ID="lblPayPeriodStartDt" runat="server"></asp:Label>
<img src="../Images/calendar.gif" class="clsCursorHand" alt="" title="Select Pay Period"
onclick="Javascript:PayPeriodsPayroll('<%=lblPayPeriodStartDt.ClientId %>',event);"/>

You are not going to get the value of the <asp:Label you modified on client side at the code behind. If I'm correct ASP.NET label is rendered as a span element in the client side:
I think that only the controls that are rendered as input controls and values changed at client side are updated on viewstate, so your only resort is to stick to the hidden field.
You just have to do the other way around.
1.Pass the hidden field to the js function and update the value of the hidden field at the client side in your js function PayPeriodsPayroll like below
function PayPeriodsPayroll (hdnObj)
{
var hdnPayPeriod = document.getElementById(hdnObj);
hdnPayPeriod.val('the value you want to set');
}
Then in your pageload
If Not IsPostBack Then
....
Else
// update label with the hidden field value if you need it
lblPayPeriodStartDt.Text = hdnPayPeriodStartDt.Value
End If

surely you are not posting back to the server every time you change the date in the calendar control.
You can do a postback to the server from javascript using the __doPostback() function.
see this link:
__doPostback function example

ASP.NET Hidden field's OnValueChange

I have several different scenarios, all with different longitudes and latitudes (and other data, but that's beside the point) in JSON. I am parsing the JSON ok, and have been able to get the desired values. What I would like to do is transfer these values to the CodeBehind.
What I am doing so far is something like this:
This is the responsible script:
function getScenarioDetails(json) {
$("#Welcome").text("Welcome user " + json.user);
$("#longitude").val(json.current_loc.lon).change();
$("#latitude").val(json.current_loc.lat).change();
}
And these are the hidden fields:
<form runat="server">
<asp:HiddenField runat="server" id="longitude" OnValueChanged="valueChanged" />
<asp:HiddenField runat="server" id="latitude" OnValueChanged="valueChanged" />
</form>
I realise that the value is being changed. But something is going wrong with the OnValueChanged as it is not firing. What exactly am I doing wrong?

I will try to explain this, First the client id is generated based on the NamingContainer parents so if your hidden fields are nested in a container you should use the property ClientIDMode and set the value to Static to ensure the client id is the same in your script.
The ValueChange event is fired when a control cause a postback so if you put a button that has the onclick event it cause a postack and the ASP.Net lifecycle starts executing the ValueChange event for your hidden inputs, Some controls as DropDownList has a property AutoPostBack when it set to true it makes a postback as soon the javascript change event happens, so it not wait until a postback occurs. The HiddeField doesn't have a AutoPostBack property so if you really need to postack after you change the values you could make a postback so:
function getScenarioDetails(json) {
$("#Welcome").text("Welcome user " + json.user);
$("#longitude").val(json.current_loc.lon);
__doPostBack('longitude', '');
.....
}

How Read Asp.net TextBox value when changed it text in clientside by javascript

i have a serverside textbox like this:
<asp:TextBox runat="server" id="testText" >hi this is a world!</asp:TextBox>
so i change this value in clienside with javascript like this
document.getElementById("<%=testText.ClientID%>").value="Hahaha"
when i read value it write like blow code in codebehind it print "hi this is a world!" value why?
response.write(testText.text); // print "hi this is a world!"

When you are rendering the text through request and response, it takes the value from server so your request and response will show the value set on server. Javascript works only on client side and once the document is loaded,it is not dependent on request and response.

your question is not clarifying to me! but suppose you have also button to change the text, you can change it according to requirment
<asp:TextBox ID="testText" runat="server" ClientIDMode="Static">hi this is a world!</asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="Button"></asp:Button>
Add an event of javascritp on your Page_Load (i am adding onclick event to button for handling javascript function)
Button1.Attributes.Add("onclick", "javascript:clientsite()");
then i think you want change server site value from client site, so for this you have to replace the value
function clientsite() {
var servervalue = document.getElementById("testText").value;
var replaceIt = servervalue.replace(servervalue, "hahaha");
document.getElementById("testText").value = replaceIt;
}
Now when you click on button it will replace or change a value from server side to client side
may be this can be helpful to you
happy coding :D

I know, this question has been asked long ago, but still adding my answer as it might be helpful to someone.
Use following line of code :
response.write(Request.Form.Get(testText.UniqueID));