Calling JavaScript Function From CodeBehind

Question

You may try this :

Page.ClientScript.RegisterStartupScript(this.GetType(),"CallMyFunction","MyFunction()",true);

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.

Calling a JavaScript function from code behind

Step 1 Add your Javascript code

<script type="text/javascript" language="javascript">
    function Func() {
        alert("hello!")
    }
</script>

Step 2 Add 1 Script Manager in your webForm and Add 1 button too

Step 3 Add this code in your button click event

ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "text", "Func()", true);

If you need to send a value as a parameter.

string jsFunc = "myFunc(" + MyBackValue + ")";
ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), "myJsFn", jsFunc, true);

You can not do this directly. In standard WebForms JavaScript is interpreted by browser and C# by server. What you can do to call a method from server using JavaScript is.

• Use WebMethod as attribute in target methods.
• Add ScriptManager setting EnablePageMethods as true.
• Add JavaScript code to call the methods through the 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 a 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 RegisterStartupScript:

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