How to stop asp.net encoding characters before outputing to html?

I have a function that generates a javascript code for me.

<img src="abc.png" alt="hello" onclick="<%: getOnCilckJS(arg)  %>" />

c# code

protected String getOnCilckJS(int arg)
{
  if (arg==1)
  {
     return "alert('hello world');";
  }
  else
  {  return "alert('hello universe');"; 
  }
}

all works fine apart from when the page is loaded asp.net converts single quotations ' to the encoded html string (')

How can I avoid this and make ' appear in the html?

Solution

Your code working to me :

But just change <%: to <%= ( and I send the parameter myself)

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="xxxx.aspx.cs" Inherits="SampleAngularApp.xxxx" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>          
        **<img src="abc.png" alt="hello" onclick="<%= getOnCilckJS(11)  %>" />**
    </div>
    </form>
</body>
</html>

Server side

**protected string getOnCilckJS(int arg)**
        {
            if (arg == 1)
            {
                return "alert('hello world');";
            }
            else
            {
                return "alert('hello universe');";
            }
        }

I got the alert message without any single quote