C# - String Slice - Dot Net Perls

String slice. A string can be sliced. To do this, we provide an extension method. By slicing a string, we extract the characters from index one to index two.

Slice notes. Taking a slice is essentially the same as calling Substring with 2 index values. But sometimes using a second argument of the last index is easier.

String Substring

Array Slice

Input and output. The key thing to remember with slice is that the second argument is an end index, not a length. And we can use a negative end index to count from the end.

Slice(1, 4) ABCDEF BCD Slice(3, -2) The morning is upon us. morning is upon u

Example. Here we develop a method in C# to match JavaScript. With the JavaScript slice method, you pass it the start index, which must always be 0 or higher.

And The second parameter can be any integer. When it is negative, it means you start from the end and then count backwards.

Note In JavaScript you can omit the second parameter. To duplicate this, create an overload that uses Length-1 as the second parameter.

Info The first character of the second test shows the first character as a space.

Detail My interpretation is that this is correct—the space is at index 3, while "m" is index 4.

using System; class Program { static void Main() { Console.WriteLine("ABCDEF".Slice(1, 4)); Console.WriteLine("The morning is upon us.".Slice(3, -2)); string s = "0123456789_"; // These slices are valid: Console.WriteLine(s.Slice(0, 1)); // First char Console.WriteLine(s.Slice(0, 2)); // First two chars Console.WriteLine(s.Slice(1, 2)); // Second char Console.WriteLine(s.Slice(8, 11)); // Last three chars } } public static class Extensions { public static string Slice(this string source, int start, int end) { // Keep this for negative end support. if (end < 0) { end = source.Length + end; } // Calculate length. int len = end - start; // Return Substring of length. return source.Substring(start, len); } }

BCD morning is upon u 0 01 1 89_

Extension notes. This is an extension method. To create an extension method, use the "this" keyword as the first parameter in a static method (in a static class).

static

Extension

Summary. Here we implemented a Slice method. An extension method makes the syntax clearer—slice is useful enough to justify an extension method.

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