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Invoke JavaScript from C# code behind [duplicate]

This question already has answers here:
Calling JavaScript Function From CodeBehind
(21 answers)
Closed 9 years ago.
I am trying to learn asp.net. Assuming that I have this code:
if (command.ExecuteNonQuery() == 0)
{
// JavaScript like alert("true");
}
else
{
// JavaScript like alert("false");
}
How to I can invoke JavaScript from C# code behind? How to do that by putting that JavaScript in Scripts directory which is created by default in MS Visual Studio?

Here is method I will use from time to time to send a pop message from the code behind. I try to avoid having to do this - but sometimes I need to.
private void LoadClientScriptMessage(string message)
{
StringBuilder script = new StringBuilder();
script.Append(#"<script language='javascript'>");
script.Append(#"alert('" + message + "');");
script.Append(#"</script>");
Page.ClientScript.RegisterStartupScript(this.GetType(), "messageScript", script.ToString());
}

You can use RegisterStartupScript to load a javascript function from CodeBehind.
Please note that javascript will only run at client side when the page is render at client's browser.
Regular Page
Page.ClientScript.RegisterStartupScript(this.GetType(), "myfunc" + UniqueID,
"myJavascriptFunction();", true);
Ajax Page
You need to use ScriptManager if you use ajax.
ScriptManager.RegisterStartupScript(Page, Page.GetType(), "myfunc" + UniqueID,
"myJavascriptFunction();", true);

Usually these "startupscripts" are handy for translations or passing settings to javascript.
Although the solution Mike provided is correct on the .Net side I doubt in a clean (read: no spaghetti code) production environment this is a good practice. It would be better to add .Net variables to a javascript object like so:
// GA example
public static string GetAnalyticsSettingsScript()
{
var settings = new StringBuilder();
var logged = ProjectContext.CurrentUser != null ? "Logged" : "Not Logged";
var account = Configuration.Configuration.GoogleAnalyticsAccount;
// check the required objects since it might not yet exist
settings.AppendLine("Project = window.Project || {};");
settings.AppendLine("Project.analytics = Project.analytics || {};");
settings.AppendLine("Project.analytics.settings = Project.analytics.settings || {};");
settings.AppendFormat("Project.analytics.settings.account = '{0}';", account);
settings.AppendLine();
settings.AppendFormat("Project.analytics.settings.logged = '{0}';", logged);
settings.AppendLine();
return settings.ToString();
}
And then use the common Page.ClientScript.RegisterStartupScript to add it to the HTML.
private void RegisterAnalyticsSettingsScript()
{
string script = GoogleAnalyticsConfiguration.GetAnalyticsSettingsScript();
if (!string.IsNullOrEmpty(script))
{
Page.ClientScript.RegisterStartupScript(GetType(), "AnalyticsSettings", script, true);
}
}
On the JavaScript side it might look like this:
// IIFE
(function($){
// 1. CONFIGURATION
var cfg = {
trackingSetup: {
account: "UA-xxx-1",
allowLinker: true,
domainName: "auto",
siteSpeedSampleRate: 100,
pluginUrl: "//www.google-analytics.com/plugins/ga/inpage_linkid.js"
},
customVariablesSetup: {
usertype: {
slot: 1,
property: "User_type",
value: "Not Logged",
scope: 1
}
}
};
// 2. DOM PROJECT OBJECT
window.Project = window.Project || {};
window.Project.analytics = {
init: function(){
// loading ga.js here with ajax
},
activate: function(){
var proj = this,
account = proj.settings.account || cfg.trackingSetup.account,
logged = proj.settings.logged || cfg.customVariablesSetup.usertype.value;
// override the cfg with settings from .net
cfg.trackingSetup.account = account;
cfg.customVariablesSetup.usertype.value = logged;
// binding events, and more ...
}
};
// 3. INITIALIZE ON LOAD
Project.analytics.init();
// 4. ACTIVATE ONCE THE DOM IS READY
$(function () {
Project.analytics.activate();
});
}(jQuery));
The advantage with this setup is you can load an asynchronous object and override the settings of this object by .Net. Using a configuration object you directly inject javascript into the object and override it when found.
This approach allows me to easily get translation strings, settings, and so on ...
It requires a little bit knowledge of both.
Please note the real power of tis approach lies in the "direct initialization" and "delayed activation". This is necessary as you might not know when (during loading of the page) these object are live. The delay helps overriding the proper objects.

This might be a long shot, but sometimes I need a c# property/value from the server side displaying or manipulated on the client side.
c# code behind page
public string Name {get; set;}
JavaScript on Aspx page
var name = '<%=Name%>';
Populating to client side is generally easier, depending on your issue. Just a thought!

how to passing value codebehind C# to javascript

Any one can help me..I want to pass the C# value to javascript..I only get pass 2 values only to the javascript..I dont know how to pass a tbSTime,tbETime and tbIndo2..Please help me..Thank You
This is code behind:
{
// get the meeting info based on the id
int id = Convert.ToInt32(Request["id"]);
MeetingClass.MeetingInfo m = MeetingClass.MeetingInfo.GetInfo(id);
// fill data
tbtitle2.Value = m.Title;
tbdate2.Value = m.Date.ToShortDateString();
tbSTime.Value = m.StartTime.ToShortTimeString();
tbETime.Value = m.EndTime.ToShortTimeString();
tbIndo2.Value = m.Desc;
}
And this is javascript:
function getInfo() {
$('#<%=tbtitle.ClientID%>').val($('#<%=tbtitle2.ClientID%>').val());
$('#<%=tbdate.ClientID%>').val($('#<%=tbdate2.ClientID%>').val());
}

From what I can tell on your code, you are setting an asp:HiddenField (since you are using .Value) and then using that to populate your asp:TextBox w/ jQuery. If that is the case, then you need to do something like this.
$('#<%=aspTextBoxName1.ClientID%>').val($('#<%=tbSTime.ClientID%>').val());
$('#<%=aspTextBoxName2.ClientID%>').val($('#<%=tbETime.ClientID%>').val());
$('#<%=aspTextBoxName3.ClientID%>').val($('#<%=tbIndo2.ClientID%>').val());
Where aspTextBoxName1, aspTextBoxName2, aspTextBoxName3 are the names of your new textboxes.
I don't know if you really need those hidden form fields, there are easier ways to do this if you don't.

in controller:
ViewBag.tbSTime = tbSTime;
in view:
$('#<%=tbtitle.ClientID%>').val("<%= ViewBag.tbSTime %>");

Iam sorry but iam not sure what exactly you need, but from what i understood i can provide you with this:
If You want to send some value from Server side variables to Javascript function one way you can do this as follows,
function abc(x,y)
{
//Do you things here
}
and from server side call javascript code as follows
string a=textbox1.text;
string b=textbox2.text;
ScriptManager.RegisterStartupScript(this, GetType(), "displayalertmessage", "abc("+a+","+b+");", true);

How to send Request.Form

I'm doing something really bad with my code. I'm getting all data posted to the actual page and putting into html inputs:
private void GetPostedForm()
{
System.Text.StringBuilder displayValues = new System.Text.StringBuilder();
System.Collections.Specialized.NameValueCollection postedValues = Request.Form;
for (int i = 0; i < postedValues.AllKeys.Length; i++)
{
String nextKey = postedValues.AllKeys[i];
if (nextKey.Substring( 0, 2 ) != "__")
{
displayValues.Append( "<input type='hidden' name='" + nextKey + "' value='" + postedValues[i] + "'/>" );
}
}
hiddensPost.InnerHtml = displayValues.ToString();
}
But the html inputs in this page are useless to me. I'm putting a page between 2 older pages ("A" sent form to "B"). Now I need to send "A" to "X" and then send to "B".
The question is: How can I put the requested form into the actual form to send to the next page without doing all this mess in HTML?

You can put your steps(A,X,B) and it's visible inputs, into separate asp-panels(pnlA,pnlX,pnlB)
then simply toggle panels visibility in which state you want.the ViewState will do it for you (store controls states into one hidden field within the form to post again with inputs)
so you may post user entered data 3 times with one html form( the famous asp.net form)
another solution is here , the asp.net wizard control

If you can, just change the method to GET and pass the QueryString along from page to page.

Javascript works on IE but not on Firefox and gives me error as Error: cprofiledetailscollapse is not defined

I use C#.net.
I wrote JavaScript for hide and show expand and collapse div accordingly. It work well in IE but not on Firefox, not even call the JavaScript function and gives me error as Error: ctl00_cpContents_dlSearchList_ctl08_profiledetailscollapse is not defined.
My JavaScript is as follows
function displayDiv(divCompact, divExpand) {
//alert('1');
var str = "ctl00_cpContents_";
var divstyle = new String();
// alert("ibtnShowHide" + ibtnShowHide);
divstyle = divCompact.style.display;
if (divstyle.toLowerCase() == "block" || divstyle == "") {
divCompact.style.display = "none";
divExpand.style.display = "block";
// ibtnShowHide.ImageUrl = "images/expand_img.GIF";
}
else {
// ibtnShowHide.ImageUrl = "images/restore_img.GIF";
divCompact.style.display = "block";
divExpand.style.display = "none";
}
return false;
}

ctl00_cpContents_dlSearchList_ctl08_profiledetailscollapse is an element id generated by ASP.NET. It's a profiledetailscollapse control inside dlSearchList.
JavaScript variable "ctl00_cpContents_dlSearchList_ctl08_profiledetailscollapse" is not
defined. Firefox does not automatically create, for each element with an id, a
variable in the global scope named after that id and containing a reference
to the element.
You might want to consider using jQuery to make sure that your DOM manipulation is cross-browser compatible.

Getting the executed output of an aspx page after a short delay

I have an aspx page which has some javascript code like
<script>
setTimeout("document.write('" + place.address + "');",1);
</script>
As it is clear from the code it will going to write something on the page after a very short delay of 1 ms. I have created an another page to get the page executed by some query string and get its output. The problem is
I can not avoid the delay as simply writing document.write(place.address); will not print anything as it takes a little time to get values so if I set it in setTimeout for delayed output of 1 ms it always return me a value
If I request the output from another page using
System.Net.WebClient wc = new System.Net.WebClient();
System.IO.StreamReader sr = new System.IO.StreamReader(wc.OpenRead("http://localhost:4859/Default.aspx?lat=" + lat + "&lng=" + lng));
string strData = sr.ReadToEnd();
I get the source code of the document instead of the desired output.
I would like to either avoid that delay or else delayed the client request output so that I get a desired value not the source code.
The JS on default.aspx is
<script type="text/javascript">
var geocoder;
var address;
function initialize() {
geocoder = new GClientGeocoder();
var qs=new Querystring();
if(qs.get("lat") && qs.get("lng"))
{
geocoder.getLocations(new GLatLng(qs.get("lat"),qs.get("lng")),showAddress);
}
else
{
document.write("Invalid Access Or Not valid lat long is provided.");
}
}
function getAddress(overlay, latlng) {
if (latlng != null) {
address = latlng;
geocoder.getLocations(latlng, showAddress);
}
}
function showAddress(r) {
place = r.Placemark[0];
setTimeout("document.write('" + place.address + "');",1);
//document.write(place.address);
}
</script>
and the code on requestClient.aspx is as
System.Net.WebClient wc = new System.Net.WebClient();
System.IO.StreamReader sr = new System.IO.StreamReader(wc.OpenRead("http://localhost:4859/Default.aspx?lat=" + lat + "&lng=" + lng));
string strData = sr.ReadToEnd();

I'm not a JavaScript expert, but I believe using document.write after the page has finished loading is a bad thing. You should be creating an html element that your JavaScript can manipulate, once the calculation is complete.
Elaboration
In your page markup, create a placeholder for where you want the address to appear:
<p id="address">Placeholder For Address</p>
In your JavaScript function, update that placeholder:
function showAddress(r) {
place = r.Placemark[0];
setTimeout("document.getElementById('address').innerHTML = '" + place.address + "';",1);
}

string strData = sr.ReadToEnd();
I get the source code of the document instead of the desired output
(Could you give a sample of the output. I don't think I've seen a web scraper work that way so that would help me to be sure. But if not this is a good example web scraper)
Exactly what are you doing with the string "strData" If you are just writing it out, I recommend you putting it in a Server side control (like a literal). If at all possible, I'd recommend you do this server side using .net rather than waiting 1 ms in javascript (which isn't ideal considering the possibility that 1 ms may or may not be an ideal amount of time to wait on a particular user's machine hence: "client side"). In a case like this and I had to do it client side I would use the element.onload event to determine if a page has finished loading.