Question

Let’s say I have an array I need to store string values as well as double values. I know I can store the doubles as strings, and just deal with the conversions, but is it possible to use an array with two data types?

Answer 1

You may use object[] and do some type checking. You will get some boxing/unboxing when accessing the doubles, but that will be faster than double.Parse() anyway.

An alternative is to create a class with both types and a marker:

class StringOrDouble
{
    private double d;
    private string s;
    private bool isString;

    StringOrDouble(double d)
    {
        this.d = d;
        isString = false;
    }

    StringOrDouble(string s)
    {
        this.s = s;
        isString = true;
    }

    double D
    {
        get
        {
            if (isString)
                throw new InvalidOperationException("this is a string");
            return d;
        }
    }

    string S
    {
        get
        {
            if (!isString)
                throw new InvalidOperationException("this is a double");
            return s;
        }
    }
    bool IsString { get { return isString; } }
}

and then create an array of StringOrDouble. This will save you from some typechecking and boxing, but will have a larger memory overhead.