Ejecutar javascript con ScriptManager

int ScriptNro = 1;
private void EjecutarScript(string js)
{
ScriptManager sm = ScriptManager.GetCurrent(this);
if (sm.IsInAsyncPostBack)
System.Web.UI.ScriptManager.RegisterClientScriptBlock(this.Page, this.Page.GetType(), "IF100" + ScriptNro.ToString(), js, true);
else
this.ClientScript.RegisterClientScriptBlock(this.Page.GetType(), "IF100" + ScriptNro.ToString(), js, true);
ScriptNro++;
}