This sample BaseClass implements some functions to register js code to ScriptManager

gistfile1.cs

public class BasePage : System.Web.UI.Page
{
  /// <summary>
	/// Creates an instance of a Base Page
	/// </summary>
	public BasePage() 
	{
		//some init logic if you want =P
	}
	
	/// <summary>
	/// Inserts the jQuery code between a $(document).ready(function()
	/// code block so its properly initiated before use
	/// </summary>
	/// <param name="jsCodetoRun"></param>
	/// <returns></returns>
	private string formatjQueryCode(string jsCodetoRun)
	{
		StringBuilder sb = new StringBuilder();
		sb.AppendLine("$(document).ready(function () {");
		sb.AppendLine(jsCodetoRun);
		sb.AppendLine(" });");

		return sb.ToString();
	}
	
	/// <summary>
	/// Registers JavaScript code in the ScriptManager according to the 
	/// type of postback 
	/// </summary>
	/// <param name="jsCodetoRun">The JavaScript code that you want to inject. 
	/// Keep in mind that all jQUery code will be put inside a $(document).ready(function() { /*jQuery code*/ }); block</param>
	/// <param name="isjQueryCode">Pass false if not jQuery but simple JavaScript</param>
	public void runJavaScriptCode(string jsCodetoRun, bool isjQueryCode=true)
	{

		ScriptManager requestSM = ScriptManager.GetCurrent(this);
		if (requestSM != null && requestSM.IsInAsyncPostBack)
		{
			ScriptManager.RegisterClientScriptBlock(this,
								typeof(Page),
								Guid.NewGuid().ToString(),
								isjQueryCode ? formatjQueryCode(jsCodetoRun) : jsCodetoRun,
								true);
		}
		else
		{
			ClientScript.RegisterClientScriptBlock(typeof(Page),
								Guid.NewGuid().ToString(),
								isjQueryCode ? formatjQueryCode(jsCodetoRun) : jsCodetoRun,
								true);
		}
	}
}