In C# is there a slick way to switch two sections of a string that are divided by a comma?

Question

I have a bunch of lat/long pairs as a string:

-94.5555,95.5555

The API I'm using requires they be switched:

95.555,-94.555

Is there any slick, short way of doing this?

Answer 1

Just write a method to do it, e.g. using string.IndexOf:

// Probably rename to reflect your specific usage
private static string SwitchSplitOnComma(string text)
{
    // Optional: validate that text is non-null
    int comma = text.IndexOf(',');
    // Optional: validate that there's a comma :)
    return text.Substring(comma + 1) + "," + text.Substring(0, comma);
}

Unless you need this for various purposes, I'd leave it as a specialist method in the class that needs it. Only promote it to a "general purpose utility method" (possibly parameterizing the delimiter etc) if you find you need the same functionality elsewhere.

Although you can do this in a single statement, I think the code is likely to be far easier to understand if you put it in a separate method - at which point it's fine to use a few easy-to-understand statements instead of one complicated and inefficient one :)

Answer 2

One-liner with Linq:

string.Join(",", original.Split(',').Reverse());

Or, more explicit (might be a performance improvement):

string[] split = original.Split(',');
string reversed = split[1] + "," + split[0];

Answer 3

string myStr = "-94.5555,95.5555";
string[] components = myStr.Split(",")
components.Reverse();
string flippedStr = string.Join(",", components);

Answer 4

String reversedLatLong = String.Join(",", yourString.Split(',').Reverse());

Answer 5

The most efficient would be to modify/extend the API, since it parses the string anyway. Probably not an option, but I throw it out there...

Answer 6

How about this?

string oldString = "-94.5555,95.5555";
string newString = oldString .Substring(oldString .IndexOf(",") + 1) + "," + oldString .Substring(0, oldString .IndexOf(","));

Answer 7

Building on Jon Skeet's, something more generic would be useful:

private static string Switch(this string text, char splitter)
{
    if(text != null && text.Length > 2) //Needs at least 3 letters for a valid switch
    {
        int position = text.IndexOf(splitter);
        if(position != -1) return text.Substring(position + 1) + splitter + text.Substring(0, position);
    }
    return text;
}

"99,-3432".Switch(',');

Answer 8

Just for the heck of it. Here's a faster version, but you probably wouldn't need it :)

For 1.000.000 iterations compared to Jon Skeets clean version measured in seconds on my machine:

00:00:00.2145657 substring

00:00:00.0781270 unsafe

private unsafe static string SwitchSplitOnComma2(string text)
{
    int comma = text.IndexOf(',');
    string newString = string.Copy(text);
    fixed (char* src = text)
    {
        fixed (char* dst = newString)
        {
            int destCtr = 0;
            for (int i = comma + 1; i < text.Length; i++)
            {
                dst[destCtr++] = src[i];
            }
            dst[destCtr++] = ',';
            for (int i = 0; i < comma; i++)
            {
                dst[destCtr++] = src[i];
            }
        }
    }
    return newString;
}