Question

I’m trying to write a validation method. Eg: for double it looks like this:

   protected bool ValidateLoopAttributes(string i_value, double i_threshold)
       {
        double result;
        if (!(double.TryParse(i_value, out result) && result >= i_threshold))
        {
            return false;
        }
        return true;
    }

Is it possible to write this as:

     protected bool ValidateLoopAttributes<T>(string i_value, T i_threshold)

and then use something like

             T.GetType().TryParse() // how can i use here the type's methods??

Is using a switch/if statement the only way to do this? Eg:

    If (T.GetType() is int) 
        Int32.TryParse(i_threshold)

Is there a more elegant way?

Answer 1

Try this:

static class Ext
{
    public static bool TryParse<T>(string s, out T value)
    {
        TypeConverter converter = TypeDescriptor.GetConverter(typeof(T));
        try
        {
            value = (T)converter.ConvertFromString(s);
            return true;
        }
        catch
        {
            value = default(T);
            return false;
        }
    }
    public static bool ValidateLoopAttributes<T>(string i_value, T i_threshold) 
           where T : IComparable
    {
        T outval;
        if (TryParse<T>(i_value, out outval))
            return outval.CompareTo(i_threshold) >= 0;
        else return false;
    }
}

My answer uses Marc Gravell’s answer taken from here.
With this you can do

bool b1 = Ext.ValidateLoopAttributes<int>("5", 4);
bool b2 = Ext.ValidateLoopAttributes<double>("5.4", 5.5d);

If you find it useful you can also use an extension method

public static bool ValidateLoopAttributes<T>(this string i_value, T i_threshold) 
       where T : IComparable { }

which leads you to use

bool b1 = "5".ValidateLoopAttributes<int>(4);
bool b2 = "5.4".ValidateLoopAttributes<double>(5.5d);