Yield is a new syntax word within the .net 2 language. This allows for the IEnumerable interface to have direct interaction instead of using the IEnumerator interface to iterate though a result set. For easier demonstration, I think, the code examples, the first code is a .net 1 version of the interface IEnumerable.<\/p>\n
\r\nusing System;\r\nusing System.Collections;\r\n\r\n\/\/ the inital class is IEnumerable- means that it has to implement the GetEnumerator\r\npublic class Class : IEnumerable \r\n{\r\n \/\/ internal class to implement the IEnumerator interface, which inturn has to do the MoveNext, Current, Reset methods.\r\n private class ClassEnumerator : IEnumerator\r\n {\r\n \/\/ internal values to go through the array\r\n private int index = -1;\r\n private Class P;\r\n \/\/ setup the internal variable\r\n public ClassEnumerator(Class P) \r\n {\r\n this.P = P; \r\n }\r\n \/\/ move within the array, if any values are present.\r\n public bool MoveNext()\r\n {\r\n index++;\r\n return index < P._Names.Length;\r\n }\r\n \/\/ set the internal to -1, thus restart\r\n public void Reset() \r\n { \r\n index = -1;\r\n }\r\n\r\n \/\/ get the Current object\r\n public object Current \r\n { \r\n get \r\n { \r\n return P._Names[index]; \r\n } \r\n }\r\n }\r\n \r\n \/\/ return a IEnumerator object of the above with itself passed\r\n public IEnumerator GetEnumerator()\r\n {\r\n return new ClassEnumerator(this);\r\n }\r\n\r\n \/\/ the internal string array of names\r\n private string[] _Names;\r\n \/\/ the new class setup process, \r\n public Class(params string[] Names)\r\n {\r\n _Names = new string[Names.Length];\r\n \/\/ copy the passed parameter starting at position 0\r\n Names.CopyTo(_Names,0);\r\n }\r\n}\r\n\r\nclass ClassProgram\r\n{\r\n static void Main(string[] args)\r\n {\r\n Class ClassArr = new Class(\"Student1\", \"Student2\",\"Studentx\");\r\n foreach (string s in ClassArr)\r\n Console.WriteLine(s);\r\n }\r\n}\r\n<\/pre>\nThis is able to output a string of <\/p>\n
\r\nStudent1\r\nStudent2\r\nStudentx\r\n<\/pre>\nSince the Class class (it is a class of students), there is allot of code to iterate with the foreach function.<\/p>\n
Within .net 2 there is a nice and more tighter method called yield, an yield will yield a result and be able to iterate though a result set with the IEnumerable return set. Again, here is the source code.<\/p>\n
\r\nusing System;\r\nusing System.Collections;\r\n\r\nclass yielding\r\n{\r\n \/\/ same as the class as in .net 1 version.\r\n public class Class : IEnumerable\r\n {\r\n \/\/ but only need to implement this one method to do the same as the pervious separate class\r\n public IEnumerator GetEnumerator()\r\n {\r\n int counter = -1;\r\n while (counter++ < (_Names.Length-1))\r\n yield return _Names[counter];\r\n }\r\n\r\n \/\/ same as the other .net 1 class internals for the private variable and the constructor\r\n private string[] _Names; \r\n public Class(params string[] Names)\r\n {\r\n _Names = new string[Names.Length];\r\n Names.CopyTo(_Names,0);\r\n }\r\n } \r\n \r\n static void Main(string[] args)\r\n {\r\n \/\/ same as the .net 1 version\r\n Class ClassArr = new Class(\"Student1\", \"Student2\", \"Studentx\");\r\n foreach (string s in ClassArr)\r\n Console.WriteLine(s);\r\n }\r\n}\r\n<\/pre>\nFar less code and also the result is exactly the same.<\/p>\n
Also there are other benefits of the yield attached to an IEnumerable interface, here is some more code to demonstrate how to implement a power function to display the power result being built up. This demonstrates how to use just a single method to return an iterate-able result.<\/p>\n
\r\nusing System;\r\nusing System.Collections;\r\n\r\nclass yielding\r\n{\r\n \/\/ same as the class as in .net 1 version.\r\n public class Class : IEnumerable\r\n {\r\n \/\/ but only need to implement this one method to do the same as the pervious separate class\r\n public IEnumerator GetEnumerator()\r\n {\r\n int counter = -1;\r\n while (counter++ < (_Names.Length-1))\r\n yield return _Names[counter];\r\n }\r\n\r\n \/\/ same as the other .net 1 class internals for the private variable and the constructor\r\n private string[] _Names; \r\n public Class(params string[] Names)\r\n {\r\n _Names = new string[Names.Length];\r\n Names.CopyTo(_Names,0);\r\n }\r\n } \r\n \r\n \/\/ IEnumerable linked to yield is new in .net 2, it allows for the \r\n \/\/ iteration of this method, acting like array instead of a single return.\r\n public static IEnumerable Power(int number, int exp)\r\n {\r\n int counter = 0, result = 1; \/\/ setup the default values.\r\n while (counter++ < exp) \/\/ increament counter and whilst lower than the passed parameter exp\r\n {\r\n result *= number; \/\/ result = result * number;\r\n yield return result; \/\/ yield the result and return\r\n }\r\n }\r\n\r\n \/\/ can also just iterate though a array of strings (in this example)\r\n public static IEnumerable StReturn(params string[] names)\r\n {\r\n int counter = -1;\r\n while (counter++ < (names.Length-1))\r\n yield return names[counter];\r\n }\r\n\r\n static void Main(string[] args)\r\n {\r\n \/\/ can do a return of a power function as well\r\n foreach(int e in Power(4,3))\r\n Console.WriteLine(e.ToString());\r\n \r\n \/\/ you can just iterate a string \r\n string[] st = {\"student1\",\"student2\",\"studentx\"};\r\n foreach(string s in StReturn(st))\r\n Console.WriteLine(s.ToString());\r\n \r\n \/\/ same as the .net 1 version\r\n Class ClassArr = new Class(\"Student1\", \"Student2\", \"Studentx\");\r\n foreach (string s in ClassArr)\r\n Console.WriteLine(s);\r\n }\r\n}\r\n<\/pre>\nI have also include the code from above to demonstrate the similar usage for iterate though a string array.<\/p>\n
Output would be<\/p>\n
\r\n4\r\n16\r\n64\r\nstudent1\r\nstudent2\r\nstudentx\r\nStudent1\r\nStudent2\r\nStudentx\r\n<\/pre>\nYou will need to have .net 2 installed or mono<\/a> (use the gmcs part of mono to use the .net 2 functions.<\/p>\n","protected":false},"excerpt":{"rendered":"Yield is a new syntax word within the .net 2 language. This allows for the IEnumerable interface to have direct interaction instead of using the IEnumerator interface to iterate though a result set. For easier demonstration, I think, the code examples, the first code is a .net 1 version of the interface IEnumerable. using System; … Continue reading Yielding results<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[14,398,13,400],"class_list":["post-176","post","type-post","status-publish","format-standard","hentry","category-c_sharp","tag-c-sharp","tag-linux","tag-mono","tag-windows"],"_links":{"self":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts\/176","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/comments?post=176"}],"version-history":[{"count":2,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts\/176\/revisions"}],"predecessor-version":[{"id":178,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/posts\/176\/revisions\/178"}],"wp:attachment":[{"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/media?parent=176"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/categories?post=176"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.codingfriends.com\/index.php\/wp-json\/wp\/v2\/tags?post=176"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}