How to parse a string into a nullable int

Solution 1:

int.TryParse is probably a tad easier:

public static int? ToNullableInt(this string s)
{
    int i;
    if (int.TryParse(s, out i)) return i;
    return null;
}

Edit @Glenn int.TryParse is "built into the framework". It and int.Parse are the way to parse strings to ints.

Solution 2:

You can do this in one line, using the conditional operator and the fact that you can cast null to a nullable type (two lines, if you don't have a pre-existing int you can reuse for the output of TryParse):

Pre C#7:

int tempVal;
int? val = Int32.TryParse(stringVal, out tempVal) ? Int32.Parse(stringVal) : (int?)null;

With C#7's updated syntax that allows you to declare an output variable in the method call, this gets even simpler.

int? val = Int32.TryParse(stringVal, out var tempVal) ? tempVal : (int?)null;

Solution 3:

[Updated to use modern C# as per @sblom's suggestion]

I had this problem and I ended up with this (after all, an if and 2 returns is soo long-winded!):

int? ToNullableInt (string val)
    => int.TryParse (val, out var i) ? (int?) i : null;

On a more serious note, try not to mix int, which is a C# keyword, with Int32, which is a .NET Framework BCL type - although it works, it just makes code look messy.

Solution 4:

C# >= 7.1

var result = int.TryParse(foo, out var f) ? f : default;

_{See C# language versioning to ascertain what language version your project supports}