OK I got the solution after some trail and errors
WebElement ddlControl= (WebElement)_driver.FindElement(By.XPath("//select[contains(@name,'controlName"));
Helper.JavaScriptClick(_driver, ddlControl);
TimeSpan timeToWait = new TimeSpan(0, 0, 10);
WebDriverWait waitForElemet = new WebDriverWait(_driver, timeToWait);
waitForElemet.Until(ExpectedConditions.ElementToBeClickable(By.XPath("//div[contains(@id,'ControlId')]//following::span[text()='50']"))).Click();