Fastest way to compare a string with an array of strings in C#2.0

Question

What is the fastest way to compare a string with an array of strings in C#2.0

Answer 1

You mean to see if the string is in the array? I can't remember if arrays support the .Contains() method, so if not, create a List< string >, add your array to the list via AddRange(), then call list.Contains({string to compare}). Will return a boolean value indicating whether or not the string is in the array.

Answer 2

//get data in list from source List checklist = Directory.GetFiles(SourcePath, ".", SearchOption.AllDirectories).Where(x => x.ToLower().EndsWith("apk")).ToList();

            //get date from a text file
           List<string>  ls = ReadFile();

            foreach(string file in checklist)
            {
                //get file name
                string filename = Path.GetFileName(file);

                string TargetLocation = Path.Combine(TargetPath, filename);

                //now compare single string to a list 
                //it give in true and false 
                if(ls.Contains(filename)) 
                {
                    //do your task
                    //File.Copy(file, TargetLocation);
                }
            }

Answer 3

If you are doing this many times with a single array, you should sort the array and binary search it:

Array.Sort(array);
int index = Array.BinarySearch(array, input);
// if (index < 0) 
//      does not exists, "items > ~index" are larger and "< ~index" are smaller
// otherwise, "items > index" are larger and "< index" are smaller.

Otherwise just check the whole array naively:

bool exists = Array.IndexOf(array, input) >= 0;

Answer 4

What kind of comparison do you want? Do you want to know if the given string is in the array?

bool targetStringInArray = array.Contains(targetString);

do you want an array of comparison values (positive, negative, zero)?

var comparisons = array.Select(x => targetString.CompareTo(x));

If you're checking for containment (i.e. the first option) and you're going to do this with multiple strings, it would probably be better to build a HashSet<string> from the array:

var stringSet = new HashSet<string>(array);

if (stringSet.Contains(firstString))  ...
if (stringSet.Contains(secondString)) ...
if (stringSet.Contains(thirdString))  ...
if (stringSet.Contains(fourthString)) ...