C# 4.0: Can I use a Color as an optional parameter with a default value? [duplicate]

This question already has answers here: 开发者_开发技巧 C# 4.0: Can I use a TimeSpan as an optional parameter with a default value? (8 answers) Closed 9 years ago.

    public void log(String msg, Color c = Color.black)
    {
        loggerText.ForeColor = c;
        loggerText.AppendText("\n" + msg);

    }

This results in an error that c must be a compile-time constant. I've read up on this a little and most examples are dealing with strings and ints. I've figured out I can use the colorconverter class but I'm not sure it will be very efficient. Is there a way to just pass a basic color as an optional parameter?

    public void log(String msg, String c = "Black")
    {
        ColorConverter conv = new ColorConverter();
        Color color = (Color)conv.ConvertFromString(c);

        loggerText.ForeColor = color;
        loggerText.AppendText("\n" + msg);
    }

---

I've run into this as well and the only workaround I've found is to use nullables.

public void log(String msg, Color? c = null)
{
    loggerText.ForeColor = c ?? Color.Black;
    loggerText.AppendText("\n" + msg);
}

Other possible syntax is:

loggerText.ForeColor = c.GetValueOrDefault(Color.Black);

---

You could check if Color is Color.Empty (which is the default value: default(Color)) or use a nullable value and check for null.

public void log(String msg, Color? c = null) { ... }

---

Don't specify the colour. Supply an "error level" instead, and have a mapping between each error level and a colour value. That way 0 and below could be black, then 1 = amber, >2 = red. No need to worry about default values and/or not specifying a value.

---

Usage suggestion:

public GraphicsLine(Point startPoint, Point endPoint, Color? color = null, double width = 1.0)
{
    StartPoint = startPoint;
    EndPoint = endPoint;
    Color = color ?? Colors.Black;
    Width = width;
}