namespace CustomAtlas.Controls
{
    public class CustomAutoCompleteProperties : AutoCompleteProperties
    {
        public string SeparatorChar
        {
            get
            {
                object obj = base.ViewState["SeparatorChar"];
                if (obj != null) return (string)obj;
                else return ",";
            }
            set
            {
                base.ViewState["SeparatorChar"] = value;
                base.OnChanged(EventArgs.Empty);
            }
        }
        public string CssList
        {
            get
            {
                object obj = base.ViewState["CssList"];
                if (obj != null) return (string)obj;
                else return String.Empty;
            }
            set
            {
                base.ViewState["CssList"] = value;
                base.OnChanged(EventArgs.Empty);
            }
        }
        public string CssItem
        {
            get
            {
                object obj = base.ViewState["CssItem"];
                if (obj != null) return (string)obj;
                else return String.Empty;
            }
            set
            {
                base.ViewState["CssItem"] = value;
                base.OnChanged(EventArgs.Empty);
            }
        }
        public string CssHoverItem
        {
            get
            {
                object obj = base.ViewState["CssHoverItem"];
                if (obj != null) return (string)obj;
                else return String.Empty;
            }
            set
            {
                base.ViewState["CssHoverItem"] = value;
                base.OnChanged(EventArgs.Empty);
            }
        }
    }
}
    

namespace CustomAtlas.Controls
{
    public class CustomAutoCompleteExtender : AutoCompleteExtender
    {
        protected override void RenderScript(
          Microsoft.Web.Script.ScriptTextWriter writer, Control targetControl)
        {
            // get our CustomAutoCompleteProperties
            CustomAutoCompleteProperties cacp = 
                (CustomAutoCompleteProperties)
                 base.GetTargetProperties(targetControl);
            if ((cacp != null) && cacp.Enabled)
            {
                // check if the ServicePath is set
                string _ServicePath = cacp.ServicePath;
                if (_ServicePath == String.Empty)
                {
                    _ServicePath = this.ServicePath;
                }
                if (_ServicePath == String.Empty)
                {
                    throw new InvalidOperationException("The ServicePath " + 
                                  "must be set for AutoCompleteBehavior");
                }
                // check if the ServiceMethod is set
                string _ServiceMethod = cacp.ServiceMethod;
                if (_ServiceMethod == String.Empty)
                {
                    _ServiceMethod = this.ServiceMethod;
                }
                if (_ServiceMethod == String.Empty)
                {
                    throw new InvalidOperationException("The ServiceMethod " + 
                                    "must be set for AutoCompleteBehavior");
                }
                // search for the completion list control if an ID was supplied
                Control c = null;
                string drp = this.DropDownPanelID;
                if (drp != String.Empty)
                {
                    c = this.NamingContainer.FindControl(drp);
                    if (c == null)
                    {
                        throw new InvalidOperationException("The specified " + 
                                       "DropDownPanelID is not a valid ID");
                    }
                }
                // write the Atlas markup on page
                writer.WriteStartElement("autoComplete");
                writer.WriteAttributeString("serviceURL", 
                    base.ResolveClientUrl(_ServicePath));
                writer.WriteAttributeString("serviceMethod", _ServiceMethod);
                if (c != null)
                  writer.WriteAttributeString("completionList", c.ClientID);
                writer.WriteAttributeString("minimumPrefixLength",
                             cacp.MinimumPrefixLength.ToString());
                writer.WriteAttributeString("separatorChar", 
                                        cacp.SeparatorChar);
                writer.WriteAttributeString("cssList", cacp.CssList);
                writer.WriteAttributeString("cssItem", cacp.CssItem);
                writer.WriteAttributeString("cssHoverItem", 
                                        cacp.CssHoverItem);
                writer.WriteEndElement();
            }
        }
    }
}
    

var text = this.control.element.value;
if ( text.lastIndexOf(_separatorChar) > -1 ) 
{
 // found separator char in the text, choosing the right word
 var pos = text.lastIndexOf(_separatorChar);
 pos++;
 text = text.substring(pos, (text.length));
text = text.trim();
}

<%@ Page Language="C#" AutoEventWireup="true" 
             CodeFile="Default.aspx.cs" Inherits="_Default" %>
<%@ Register Namespace="CustomAtlas.Controls" TagPrefix="customAtlas" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" 
     "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>CustomAutoCompleteExtender</title>
    <link href="StyleSheet.css" rel="stylesheet" type="text/css" />
</head>
<body>
    <form id="form1" runat="server">
        <atlas:ScriptManager ID="scriptManager" runat="server">
            <Scripts>
                <atlas:ScriptReference ScriptName="Custom" />
                <atlas:ScriptReference 
                   Path="scriptLibrary/CustomAutoCompleteBehavior.js" />
            </Scripts>
        </atlas:ScriptManager>
        
        <div>
            <asp:TextBox ID="txtSuggestions" 
                     runat="server"></asp:TextBox>
            <customAtlas:CustomAutoCompleteExtender 
                   ID="CustomAutoCompleteExtender1" runat="server">
                <customAtlas:CustomAutoCompleteProperties
                                 TargetControlID="txtSuggestions"
                                 ServicePath="WebServiceDemo.asmx"
                                 ServiceMethod="GetSuggestions"
                                 MinimumPrefixLength="1"
                                 SeparatorChar=","
                                 CssList="autoCompleteList"
                                 CssItem="autoCompleteItem" 
                                 CssHoverItem="autoCompleteHoverItem"
                                 Enabled="true" />
            </customAtlas:CustomAutoCompleteExtender>       
        </div>
    </form>
</body>
</html>