What is the most efficient way to separate the int from this string?

Question

I have a string in this format: "ABC_123_"

I want to end up with and integer variable that is just the number portion of the string. What is the most efficient way to accomplish that in C#?

Answer 1

This should be efficient enough. Don't sweat if it's not the most efficient unless profiling tells you that it's a bottleneck of your application:

string s = "ABC_123_";
int i = Int32.Parse(s.Split('_')[1]);

Without more information about your problem, this is what I would go with.

Answer 2

If your string input will always be in the same form of ABC_123_ then this will work

int i = Int32.Parse("ABC_123_".Substring(4, 3));

Answer 3

If the lenght of your string etc. are fixed, you can use String.Substring.

The more complicated your string gets, the more you should use Regex.

Answer 4

Here's one way. I don't know about "most efficient", but it should work:

int? GetJustIntPart(string original)
{
    var split = original.Split('_');
    int test;
    foreach (var item in split)
    {
        if (int.TryParse(item, out test))
            return test;
    }
    return null;
}

Answer 5

Mandatory RegEx example to match all numbers in a string:

int num = Convert.ToInt32(Regex.Match("ABC_123_", @"\d+").Value);

Change to make sure it's surrounded by _:

int num = Convert.ToInt32(Regex.Match("ABC_123_", @"(?<=_)\d+(?=_)").Value);

Note: Value may be null/empty if your input string is in an improper format, so use int.TryParse or try/catch etc.

Answer 6

I'd go with int i = int.Parse(Regex.Match(string,@"\d+"));