Calling JavaScript Function From CodeBehind

C# to JavaScript: you can register script block to run on page like following:

ClientScript.RegisterStartupScript(GetType(),"hwa","alert('Hello World');",true);

replace alert() part with your function name.

For calling C# method from JavaScript you can use ScriptManager or jQuery. I personally use jQuery. You need to decorate the method that you want to call from JavaScript with WebMethod attribute. For more information regarding calling C# method (called PageMethod) from jQuery you can refer to Dave Ward's post.

IIRC Code Behind is compiled serverside and javascript is interpreted client side. This means there is no direct link between the two.

What you can do on the other hand is have the client and server communicate through a nifty tool called AJAX. http://nl.wikipedia.org/wiki/Asynchronous_JavaScript_and_XML

You cannot. Codebehind is running on the server while JavaScript is running on the client.

However, you can add <script type="text/javascript">someFunction();</script> to your output and thus cause the JS function to be called when the browser is parsing your markup.

You cannot do this directly. Javascript is interpreted by browser and C# by server. What you can do to call a method from server using javscript is

• use webmethod as attribute in target methods.
• add scriptmanager setting EnablePageMethods as true
• add javascript code to call the methods through object PageMethods

Like this: step 1

 public partial class Products : System.Web.UI.Page 
   { 
     [System.Web.Services.WebMethod()] 
     [System.Web.Script.Services.ScriptMethod()] 
     public static List<Product> GetProducts(int cateogryID) 
     {
       // Put your logic here to get the Product list 
     }

step 2: adding scriptmanager on the page

 <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePageMethods="true" />

step 3: calling the method using javascript

function GetProductsByCategoryID(categoryID)
{
    PageMethods.GetProducts(categoryID, OnGetProductsComplete);
}

Take a look at this link.

To call a javascript function from server you can use a RegisterStartipScript:

ClientScript.RegisterStartupScript(GetType(),"id","callMyJSFunction()",true);

You can't call a Javascript function from the CodeBehind, because the CodeBehind file contains the code that executes server side on the web server. Javascript code executes in the web browser on the client side.

You can expose C# methods on codebehind pages to be callable via JavaScript by using the ScriptMethod attribute.

You cannot call JavaScript from a CodeBehind - that code exists solely on the client.

This is how i call a JS file from C#. Hope that is useful for you:

    public static void actualizarTarjeta(csTarjeta tarjeta)
    {

        string nombreArchivo = "badge.js";

        File.WriteAllText(nombreArchivo, tarjeta.setFileActualizarTarjeta(tarjeta.NroTarjeta.ToString(), tarjeta.Estado.ToString()));


        Process proc = new Process();

        ProcessStartInfo startInfo = new ProcessStartInfo();
        startInfo.CreateNoWindow = true;
        startInfo.UseShellExecute = false;
        startInfo.RedirectStandardOutput = true;
        startInfo.RedirectStandardError = true;
        startInfo.FileName = "cscript.exe";
        startInfo.Arguments = nombreArchivo;
        startInfo.WindowStyle = ProcessWindowStyle.Hidden;
        proc.StartInfo = startInfo;
        proc.Start();
        proc.WaitForExit(500);
        proc.Close();
        proc.Dispose();
    }

    public string setFileActualizarTarjeta(string id, string estado)
    {
        dataFileOut = "var wbemServices = GetObject(\"winmgmts://./root/onguard\");";
        dataFileOut += " var badgeSet = wbemServices.ExecQuery(\"select * from Lnl_Badge where ID=" + id + "\");";
        dataFileOut += " for ( var e = new Enumerator( badgeSet ); !e.atEnd(); e.moveNext() ){";
        dataFileOut += " var badge = e.item();";
        dataFileOut += " badge.Status=" + estado + ";";
        dataFileOut += " badge.Put_(); }";

        return dataFileOut;
    }

This is how I've done it.

HTML markup showing a label and button control is as follows.

<body> 
  <form id="form1" runat="server"> 
  <div> 
    <asp:Label ID="lblJavaScript" runat="server" Text=""></asp:Label> 
    <asp:Button ID="btnShowDialogue" runat="server" Text="Show Dialogue" /> 
  </div> 
  </form> 
</body>

JavaScript function is here.

<head runat="server"> 
  <title>Calling javascript function from code behind example</title> 
  <script type="text/javascript"> 
    function showDialogue() { 
      alert("this dialogue has been invoked through codebehind."); 
    } 
  </script> 
</head>

Code behind to trigger the JavaScript function is here.

lblJavaScript.Text = "<script type='text/javascript'>showDialogue();</script>";