InputSelectNumber.cs

public class InputSelectNumber<T> : InputSelect<T>
{
    protected override bool TryParseValueFromString(string value, out T result, out string validationErrorMessage)
    {
        if (typeof(T) == typeof(int))
        {
            if (int.TryParse(value, out var resultInt))
            {
                result = (T)(object)resultInt;
                validationErrorMessage = null;
                return true;
            }
            else
            {
                result = default;
                validationErrorMessage = "The chosen value is not a valid number.";
                return false;
            }
        }
        else
        {
            return base.TryParseValueFromString(value, out result, out validationErrorMessage);
        }
    }
}