Question

I’m trying to make a method faster. Right now, it takes an object obj and converts it to a double with the following:

double val = Convert.ToDouble(obj);

Would it be faster if I did this?

double val = double.Parse(obj.ToString());

Answer 1

For string Convert.ToDouble just checks value for null and return 0.0 if so. Then it really calls double.Parse:

[__DynamicallyInvokable]
public static double ToDouble(object value)
{
  if (value != null)
    return ((IConvertible) value).ToDouble((IFormatProvider) null);
  else
    return 0.0;
}

// common implementation of IConvertable
double IConvertible.ToDouble(IFormatProvider provider)
{
  return Convert.ToDouble(this, provider);
}

// implementation for string
[__DynamicallyInvokable]
public static double ToDouble(string value, IFormatProvider provider)
{
  if (value == null)
    return 0.0;
  else
    return double.Parse(value, NumberStyles.Float | NumberStyles.AllowThousands, provider);
}

// and for long. differs, right? 
[__DynamicallyInvokable]
public static double ToDouble(long value)
{
  return (double) value;
}

So I don’t think that double.Parse if much faster for non-number types. But when you don’t really know that type your argument is, it’s better to call Convert.ToDouble(value) instead of double.Parse(value.ToString()).