Switch case and generics checking

Question

I want to write a function that format int and decimal differently into string

I have this code:

and I want to rewrite it to generi

Answer 1

You could check the type of the variabele;

    public static string FormatWithCommaSeperator<T>(T value)
    {
        if (value is int)
        {
            // Do your int formatting here
        }
        else if (value is decimal)
        {
            // Do your decimal formatting here
        }
        return "Parameter 'value' is not an integer or decimal"; // Or throw an exception of some kind?
    }

Answer 2

Edit: If you only want to handle exactly int and double, just have two overloads:

DoFormat(int value)
{
}

DoFormat(double value)
{
}

---

If you insist on using generics:

switch (value.GetType().Name)
{
    case "Int32":
        break;
    case "Double":
        break;
    default:
        break;
}

OR

if (value is int)
{
    int iValue = (int)(object)value;
}
else if (value is double)
{
    double dValue = (double)(object)value;
}
else
{
}

Answer 3

Another way to do switch on generic is:

switch (typeof(T))
{
    case Type intType when intType == typeof(int):
        ...
    case Type decimalType when decimalType == typeof(decimal):
        ...
    default:
        ...
}

Answer 4

In modern C#:

public static string FormatWithCommaSeperator<T>(T value) where T : struct
{
    switch (value)
    {
        case int i:
            return $"integer {i}";
        case double d:
            return $"double {d}";
    }
}

Answer 5

Alternatively you could always do:

public static string FormatWithCommaSeparator<T>(T[] items)
{
    var itemArray = items.Select(i => i.ToString());

    return string.Join(", ", itemArray);
}

Answer 6

You could instead of using generics use IConvertible

    public static string FormatWithCommaSeperator(IConvertible value)
    {
            IConvertible convertable = value as IConvertible;
            if(value is int)
            {
                int iValue = convertable.ToInt32(null);
                //Return with format.
            }
            .....
    }