I need to sometimes set the value of an int to null and sometimes to an actual value. The problem is I need to store that value in the SAME variable not create another.
int? year;
if(something)
year = null;
else
int.tryParse("some string", out year);
"some string" is always a valid int but the problem is I can't use int.tryParse on int? How to get around that?
If your string will always be a valid integer, you should just use the Parse method.
year = int.Parse("some string");
In the case that it’s not a valid integer, you will get a FormatException or OverflowException (unlike TryParse, which merely returns false).
TryParse (which still needs to perform validation). It may be less efficient than a manual implementation that skips all validation checks, but it’s usually not worth the trouble.Parse and TryParse, and apart from throwing vs returning false, they’re identical.
Parse says "This will always be valid. If it's invalid, we have a bug, so no need to handle that case." whereas TryParse says "It can sometimes be invalid, and I've added explicit error handling for it". In most cases the right choice is quite obvious, and since the OP said that the value is guaranteed to be a valid int, Parse is clearly the better choice here.You can use Convert.ToInt32(year).
You could try this:
public class NullInt
{
public void ParseInt(string someString, ref int? someInt)
{
int i;
if (int.TryParse(someString, out i))
{
someInt = i;
}
}
}
and used somewhat like:
NullInt someInt = new NullInt();
int? targetInt = null;
someInt.ParseInt("42", ref targetInt);
If "some string" is always a valid int, then you COULD just convert it to an int, using System.Convert.ToInt32 or System.Int32.Parse
int.tryParse returns a boolean, not just the out value - you can do this also:
int year;
int? finalYear;
if(int.TryParse("some string", out year))
finalYear = year;
otherwise, if "some string" will always return a valid int, why not do
int? year = int.Parse("some string");
public static class StringExtensions
{
public static int? AsInt(this string input)
{
int number;
if (int.TryParse(input, out number))
{
return number;
}
return null;
}
}
Usage: year = someString.AsInt();
This seems to work also:
int? year;
if (something)
year = null;
else
{
int _year;
int.TryParse(year.SelectedItem.Value, out _year);
year = _year;
}
TryParse without checking the result is only a good idea if you want the value to become default(T), which isn't the case here. You're just hiding a bug if that happens.Add in some error detection:
try
{
year = int.Parse("some string");
}
catch()
{
year = null;
}
"some string"is never a valid int. (Except perhaps when using Eldritch culture)