How to set optional parameter without compile-time constant

Question

Is there a way to write the C# method below:

public string Download(Encoding contentEncoding = null) {
    defaultEncoding = contentEncoding ?? Encoding.UTF8         


        

Answer 1

public static string Download(Encoding encoder = null)
{
    if (encoder == null)
        encoder = Encoding.Default


   string returnVal="";
   // do something

    return returnVal;
}