When do we use reference parameter?

Sometimes you need to get more than one piece of data from a function, for example imagine a function called GetNewColorAndText...

You can return the color from the function or you can return the text, but not easily both. This illustrates:

        public static string GetNewColorAndText(ref Color Col, string sText)
        {
            Col = Color.FromArgb (255,Col.R/2,Col.G/2,Col.B/2) 
            string sRet = sText + "and darker" ;
            return sRet ;
        }

        public static void Test()
        {
            Color MyCol = Color.FromArgb(255, 45, 67, 89);
            string sDesc = "a color";

            string sNewDesc = GetNewColorAndText(ref MyCol, sDesc);
        
            // Now MyCol will have a different value from before
            // the call
        }

MyCol is changed by the call to GetNewColorAndText.

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