Comparing two string arrays in C#

Question

Say we have 5 string arrays as such:

string[] a = {"The","Big", "Ant"};
string[] b = {"Big","Ant","Ran"};
string[] c = {"The","Big","Ant"};
string[] d = {"No","Ants","Here"};
string[] e = {"The", "Big", "Ant", "Ran", "Too", "Far"};

Is there a method to compare these strings to each other without looping through them in C# such that only a and c would yield the boolean true? In other words, all elements must be equal and the array must be the same size? Again, without using a loop if possible.

You could simplify the comparison using string.Join and you could get away from loops using Linq but under the hood you are still looping - are you trying to do it without loops for a reason? — Charleh
– Charleh, Commented Jun 20, 2013 at 11:21
look like duplicate as stackoverflow.com/questions/2913287/… and stackoverflow.com/questions/713341/comparing-arrays-in-c-sharp — Atish Kumar Dipongkor
– Atish Kumar Dipongkor, Commented Jun 20, 2013 at 11:49

Ahmed KRAIEM · Accepted Answer · 2013-06-20 11:20:19Z

116

You can use Linq:

bool areEqual = a.SequenceEqual(b);

answered Jun 20, 2013 at 11:20

Ahmed KRAIEM

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4 Comments

Tim Schmelter Over a year ago

@WesField: Note that this method also loops, just because your requirement was "without looping". Of course it's impossible to compare multiple items without looping. Also note that it uses the default comparer by default which works for value types and the .NET types. For custom reference types you need to create a custom IEqualityComparer<T> for SequenceEqual and/or override Equals and GetHashCode.

Wes Field Over a year ago

@TimSchmelter: Yeah, I realize that a loop is being executed behind the scenes, I just wanted something neat and pretty-looking without room for a muck up.

tdgtyugdyugdrugdr Over a year ago

Returns false when two arrays have exactly same values, but in different order.

Nelson Over a year ago

"Without looping" is handy when you need to construct an Expression<Func<TIn,TOut>>. This is what I ended up doing for Mock.Is<T> from the Moq library.

Darren · Accepted Answer · 2013-11-18 15:30:38Z

25

Try using Enumerable.SequenceEqual:

var equal = Enumerable.SequenceEqual(a, b);

edited Nov 18, 2013 at 15:30

answered Jun 20, 2013 at 11:21

Darren

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3 Comments

Wes Field Over a year ago

Also a good answer. Could you explain the differences between this and the Linq a.SequenceEqual(b)?

Charleh Over a year ago

Same thing - ones using the extension method syntax, the other is using the extension method explicitly. Look at extension method sig for details msdn.microsoft.com/en-us/library/vstudio/bb383977.aspx

Tim Schmelter Over a year ago

@WesField: There's no difference. An extension method is just a static method in a static class. So you can treat it as a normal static method(this answer) or you use it as extension method(Ahmed's answer).

Manish Vadher · Accepted Answer · 2018-03-17 09:05:48Z

6

if you want to get array data that differ from another array you can try .Except

string[] array1 = { "aa", "bb", "cc" };
string[] array2 = { "aa" };

string[] DifferArray = array1.Except(array2).ToArray();

Output: {"bb","cc"}

answered Mar 17, 2018 at 9:05

Manish Vadher

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2 Comments

Медведев Александр Over a year ago

string[] a = new string[] {"1","2","2"}; string[] b = new string[] {"1","2"};  string[] DifferArray = a.Except(b).ToArray();

DifferArray.Length; // 0 it's bad case

avr-girl Over a year ago

Longer list needs to be in front or it won't work, eg LongerList.Except(shorterList).ToArray();

Charleh · Accepted Answer · 2013-06-20 11:34:27Z

3

If you want to compare them all in one go:

string[] a = { "The", "Big", "Ant" };
string[] b = { "Big", "Ant", "Ran" };
string[] c = { "The", "Big", "Ant" };
string[] d = { "No", "Ants", "Here" };
string[] e = { "The", "Big", "Ant", "Ran", "Too", "Far" };

// Add the strings to an IEnumerable (just used List<T> here)
var strings = new List<string[]> { a, b, c, d, e };

// Find all string arrays which match the sequence in a list of string arrays
// that doesn't contain the original string array (by ref)
var eq = strings.Where(toCheck => 
                            strings.Where(x => x != toCheck)
                            .Any(y => y.SequenceEqual(toCheck))
                      );

Returns both matches (you could probably expand this to exclude items which already matched I suppose)

answered Jun 20, 2013 at 11:34

Charleh

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1 Comment

Wes Field Over a year ago

Thanks, probably won't use that this time, but it is a nifty option.

Dejan Ciev · Accepted Answer · 2013-06-22 16:13:57Z

-2

        if (a.Length == d.Length)
        {
            var result = a.Except(d).ToArray();
            if (result.Count() == 0)
            {
                Console.WriteLine("OK");
            }
            else
            {
                Console.WriteLine("NO");
            }
        }
        else
        {
            Console.WriteLine("NO");
        }

answered Jun 22, 2013 at 16:13

Dejan Ciev

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