CODEWITHSUNDEEP
c#javascript.netasp.netcode-behind
David Hodgson
David Hodgson

Reputation: 10344

Passing arguments to JavaScript function from code-behind

I would like to call a javascript function from an aspx control. For instance, suppose I had:

<html xmlns="http://www.w3.org/1999/xhtml">
    <head runat="server">
<title>Untitled Page</title>
<script type="text/javascript">
    function test(x, y)
    {

    }
</script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Button ID="Button1" runat="server" Text="Button"
         onclick="Button1_Click"/>
    </div>
    </form>
</body>
</html>

and in the code behind:

protected void Button1_Click(object sender, EventArgs e)
{
    // do stuff (really going to a database to fill x and y)
    int[] x = new int[] { 1, 2, 3, 4, 5 };
    int[] y = new int[] { 1, 2, 3, 4, 5 };

    // call javascript function as test(x,y);
}

Is there a way to do it?

Upvotes: 11

Views: 106305

Answers (9)

Bhushan Mahajan
Bhushan Mahajan

Reputation: 67

 <head>
    <script type="text/javascript">

        function test(x, y) 
        {
            var cc = "";
            for (var i = 0; i < x.length; i++) 
            {
                cc += x[i]; 
            }
            cc += "\ny: " + y; 
            return cc;
        }

    </script>



</head>

<body>

    <form id="form1" runat="server">

        <asp:Button ID="Button1" runat="server" Text="Button"   />

        <p>
             <asp:TextBox ID="TextBox1"  Name="TextBox1"  runat="server" AutoPostBack="True"  TextMode="MultiLine"></asp:TextBox>
        </p>



    </form>
</body>

protected void Page_Load(object sender, EventArgs e)
{
    int[] x = new int[] { 1, 2, 3, 4, 5 };
    int[] y = new int[] { 1, 2, 3, 4, 5 };

    string xStr = getArrayString(x); // converts {1,2,3,4,5} to [1,2,3,4,5]
    string yStr = getArrayString(y);

    string script = String.Format(" var y = test({0},{1}) ; ", xStr, yStr);
    script += String.Format("  document.getElementById(\"TextBox1\").value = y  ");

    this.Page.ClientScript.RegisterStartupScript(this.GetType(),  "testFunction", script, true);
  //  this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "testFunction", script, true); // different result
}




private string getArrayString(int[] array)
{
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < array.Length; i++)
    {
        sb.Append(array[i] + ",");
    }
    string arrayStr = string.Format("[{0}]", sb.ToString().TrimEnd(','));
    return arrayStr;
}

Upvotes: 0

sunny
sunny

Reputation: 11

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Call java script function on Code behind</title>
    <script  type="text/javascript">
    function abc()
    {
        var a=20;
        var b=30;
        alert("you enter"+a+":"+b);
    }
    </script>
</head>

cs code

protected void Page_Load(object sender, EventArgs e)
{
    TextBox2.Attributes.Add("onkeypress", "return abc();");
}

try this

Upvotes: 1

Sai Sherlekar
Sai Sherlekar

Reputation: 1844

include script manager

code behind function

ScriptManager.RegisterStartupScript(this, this.GetType(), "HideConfirmBox", "javascript:HideAAConfirmBox(); ", true);

Upvotes: 3

David Robbins
David Robbins

Reputation: 10046

If you are interested in processing Javascript on the server, there is a new open source library called Jint that allows you to execute server side Javascript. Basically it is a Javascript interpreter written in C#. I have been testing it and so far it looks quite promising.

Here's the description from the site:

Differences with other script engines:

Jint is different as it doesn't use CodeDomProvider technique which is using compilation under the hood and thus leads to memory leaks as the compiled assemblies can't be unloaded. Moreover, using this technique prevents using dynamically types variables the way JavaScript does, allowing more flexibility in your scripts. On the opposite, Jint embeds it's own parsing logic, and really interprets the scripts. Jint uses the famous ANTLR (http://www.antlr.org) library for this purpose. As it uses Javascript as its language you don't have to learn a new language, it has proven to be very powerful for scripting purposes, and you can use several text editors for syntax checking.

Upvotes: 0

Dave L
Dave L

Reputation: 1634

Look at the ScriptManager.RegisterStartupScript method if you're using a ScriptManager or any Ajax controls/asynchronous postbacks.

Edit:

Actually, the function you want is probably ScriptManager.RegisterClientScriptBlock

Upvotes: 10

David Hodgson
David Hodgson

Reputation: 10344

Some other things I found out:

You can't directly pass in an array like:

this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "xx",   
"<script>test("+x+","+y+");</script>");

because that calls the ToString() methods of x and y, which returns "System.Int32[]", and obviously Javascript can't use that. I had to pass in the arrays as strings, like "[1,2,3,4,5]", so I wrote a helper method to do the conversion.

Also, there is a difference between this.Page.ClientScript.RegisterStartupScript() and this.Page.ClientScript.RegisterClientScriptBlock() - the former places the script at the bottom of the page, which I need in order to be able to access the controls (like with document.getElementByID). RegisterClientScriptBlock() is executed before the tags are rendered, so I actually get a Javascript error if I use that method.

http://www.wrox.com/WileyCDA/Section/Manipulating-ASP-NET-Pages-and-Server-Controls-with-JavaScript.id-310803.html covers the difference between the two pretty well.

Here's the complete example I came up with:

// code behind
protected void Button1_Click(object sender, EventArgs e)
{
    int[] x = new int[] { 1, 2, 3, 4, 5 };
    int[] y = new int[] { 1, 2, 3, 4, 5 };

    string xStr = getArrayString(x); // converts {1,2,3,4,5} to [1,2,3,4,5]
    string yStr = getArrayString(y);

    string script = String.Format("test({0},{1})", xStr, yStr);
    this.Page.ClientScript.RegisterStartupScript(this.GetType(),
    "testFunction", script, true);
    //this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(),
    //"testFunction", script, true); // different result
}
private string getArrayString(int[] array)
{
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < array.Length; i++)
    {
        sb.Append(array[i] + ",");
    }
    string arrayStr = string.Format("[{0}]", sb.ToString().TrimEnd(','));
    return arrayStr;
}

//aspx page
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>
    <script type="text/javascript">
    function test(x, y)
    {
        var text1 = document.getElementById("text1")
        for(var i = 0; i<x.length; i++)
        {
            text1.innerText += x[i]; // prints 12345
        }
        text1.innerText += "\ny: " + y; // prints y: 1,2,3,4,5

    }

    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Button ID="Button1" runat="server" Text="Button"
         onclick="Button1_Click" />
    </div>
    <div id ="text1"> 
    </div>
    </form>
</body>
</html>

Upvotes: 6

Thomas Stock
Thomas Stock

Reputation: 11256

I think you want to execute the javascript serverside and not in the browser after post-back, right?

That's not possible as far as I know

If you just want to get it execute after postback, you can do something like this:

this.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "xx", "<script>test("+x+","+y+");</script>");

Upvotes: 0

Chad Grant
Chad Grant

Reputation: 45382

Response.Write("<scrip" + "t>test(" + x + "," + y + ");</script>");

breaking up the script keyword because VStudio / asp.net compiler doesn't like it

Upvotes: 2

Kirtan
Kirtan

Reputation: 21695

You can use the Page.ClientScript.RegisterStartupScript method.

Upvotes: 10

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