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c#arrays
dotcoder
dotcoder

Reputation: 2921

how to take all array elements except last element in C#

I have a string array like this.

string[] queries with data more than one string.

I want to skip the last string from the element and take the remaining. I have come up with

var remStrings = queries.Reverse().Skip(1).Take(queries.Length - 1);

Is there a better alternative to this?

Upvotes: 80

Views: 71630

Answers (7)

Umut D.
Umut D.

Reputation: 1846

Maybe this is an indirect solution. However, a different approach without using extension.

// Convert string array to generic list
List<string> queries = new[] { "a", "b", "c", "d", "e" }.ToList();

var lastElement = queries.LastOrDefault();
var takeAllExceptLastElement = queries.Take(queries.LastIndexOf(lastElement));
        
Console.WriteLine(string.Join(",", takeAllExceptLastElement));

Upvotes: 0

user1781290
user1781290

Reputation: 2864

For anyone finding this now...

With the upcoming support for ranges and indices C# 8 and .NET Core 3.0 you can simply write

var remStrings = queries[..^1]

This is short for 

var remStrings = queries[0..^1]

This works by converting the 0 and 1 to indices (System.Index), with the ^ being the marker (actually an operator) to index from the end of a sequence. From these indices a range (System.Range) is then generates which can then be used to access the array. (See https://learn.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-8#indices-and-ranges)

Currently this only works in the preview version of .NET Core 3.0

Upvotes: 53

FrostyOnion
FrostyOnion

Reputation: 996

Edited: You could effectively replace your array with the same array minus the last element with the following line or code:

queries = queries.Take(queries.Length - 1).ToArray();

If you would like to create a method that does this for you, then you could use the following:

public static string[] TrimLastElement(string[] arr) {
    return arr.Take(arr.Length - 1).ToArray();
}

And implement it in your code like so:

queries = TrimLastElement(queries);

Upvotes: 0

Enigmativity
Enigmativity

Reputation: 117027

Microsoft's Reactive Extensions' Team has the Interactive Extensions (NuGet "System.Interactive") that lets you do this:

var remStrings = queries.SkipLast(1);

Upvotes: 15

Erwin Mayer
Erwin Mayer

Reputation: 18670

This answer from a related post is also worth mentioning as it elegantly applies to any IEnumerable in a single pass, without the need to know its number of elements beforehand.

Upvotes: 3

ChrisF
ChrisF

Reputation: 137128

Why not just have:

var remStrings = queries.Take(queries.Length-1);

Which will return them in the same order.

Append .Reverse() to swap the order if that's a necessary requirement:

var remStrings = queries.Take(queries.Length-1).Reverse();

Upvotes: 12

Justin Niessner
Justin Niessner

Reputation: 245399

var remStrings = queries.Take(queries.Length - 1);

No need to Reverse and Skip. Just take one less element than there are in the array.

If you really wanted the elements in the reverse order, you could tack on a .Reverse() to the end.

Upvotes: 136

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