What does yield break do in C

Question

I have seen this syntax in MSDN  yield break  but I don t know what it does   Does anyone know

User · Answer

Ends an iterator block  e g  says there are no more elements in the IEnumerable

User · Answer

It specifies that an iterator has come to an end  You can think of yield break as a return statement which does not return a value   For example  if you define a function as an iterator  the body of the function may look like this   for  int i   0  i  lt  5  i          yield return i     Console Out WriteLine  You will see me      Note that after the loop has completed all its cycles  the last line gets executed and you will see the message in your console app   Or like this with yield break   int i   0  while  true        if  i  lt  5                yield return i            else                  note that i   will not be executed after this         yield break            i       Console Out WriteLine  Won t see me      In this case the last statement is never executed because we left the function early

User · Answer

It specifies that an iterator has come to an end  You can think of yield break as a return statement which does not return a value   For example  if you define a function as an iterator  the body of the function may look like this   for  int i   0  i  lt  5  i          yield return i     Console Out WriteLine  You will see me      Note that after the loop has completed all its cycles  the last line gets executed and you will see the message in your console app   Or like this with yield break   int i   0  while  true        if  i  lt  5                yield return i            else                  note that i   will not be executed after this         yield break            i       Console Out WriteLine  Won t see me      In this case the last statement is never executed because we left the function early

User · Answer

Tells the iterator that it s reached the end   As an example   public interface INode       IEnumerable lt Node gt  GetChildren       public class NodeWithTenChildren   INode       private Node   m children   new Node 10        public IEnumerable lt Node gt  GetChildren                 for  int n   0  n  lt  10    n                         yield return m children  n                       public class NodeWithNoChildren   INode       public IEnumerable lt Node gt  GetChildren                 yield break

User · Answer

Here http   www alteridem net 2007 08 22 the-yield-statement-in-c  is very good example    public static IEnumerable lt int  Range  int min  int max        while   true              if   min    max                    yield break                yield return min             and explanation  that if a yield break statement is hit within a method  execution of that method stops with no return  There are some time situations  when you don t want to give any result  then you can use yield break

User · Answer

yield basically makes an IEnumerable lt T gt  method behave similarly to a cooperatively  as opposed to preemptively  scheduled thread   yield return is like a thread calling a  schedule  or  sleep  function to give up control of the CPU   Just like a thread  the IEnumerable lt T gt  method regains controls at the point immediately afterward  with all local variables having the same values as they had before control was given up   yield break is like a thread reaching the end of its function and terminating   People talk about a  state machine   but a state machine is all a  thread  really is   A thread has some state  I e  values of local variables   and each time it is scheduled it takes some action s  in order to reach a new state   The key point about yield is that  unlike the operating system threads we re used to  the code that uses it is frozen in time until the iteration is manually advanced or terminated

User · Answer

Here http   www alteridem net 2007 08 22 the-yield-statement-in-c  is very good example    public static IEnumerable lt int  Range  int min  int max        while   true              if   min    max                    yield break                yield return min             and explanation  that if a yield break statement is hit within a method  execution of that method stops with no return  There are some time situations  when you don t want to give any result  then you can use yield break

User · Answer

The yield keyword is used together with the return keyword to provide a value to the enumerator object  yield return specifies the value  or values  returned  When the yield return statement is reached  the current location is stored  Execution is restarted from this location the next time the iterator is called   To explain the meaning using an example        public IEnumerable lt int gt  SampleNumbers                 int counter   0          yield return counter           counter   counter   2           yield return counter           counter   counter   3           yield return counter            Values returned when this is iterated are  0  2  5   It   s important to note that counter variable in this example is a local variable  After the second iteration which returns the value of 2  third iteration starts from where it left before  while preserving the previous value of local variable named counter which was 2

User · Answer

The yield break statement causes the enumeration to stop  In effect  yield break completes the enumeration without returning any additional items   Consider that there are actually two ways that an iterator method could stop iterating  In one case  the logic of the method could naturally exit the method after returning all the items  Here is an example   IEnumerable lt uint gt  FindPrimes uint startAt  uint maxCount        for  var i   0UL  i  lt  maxCount  i                  startAt   NextPrime startAt           yield return startAt             Debug WriteLine  All the primes were found         In the above example  the iterator method will naturally stop executing once maxCount primes have been found   The yield break statement is another way for the iterator to cease enumerating  It is a way to break out of the enumeration early  Here is the same method as above  This time  the method has a limit on the amount of time that the method can execute    IEnumerable lt uint gt  FindPrimes uint startAt  uint maxCount  int maxMinutes        var sw   System Diagnostics Stopwatch StartNew        for  var i   0UL  i  lt  maxCount  i                  startAt   NextPrime startAt           yield return startAt           if  sw Elapsed TotalMinutes  gt  maxMinutes              yield break             Debug WriteLine  All the primes were found         Notice the call to yield break  In effect  it is exiting the enumeration early   Notice too that the yield break works differently than just a plain break  In the above example  yield break exits the method without making the call to Debug WriteLine

User · Answer

The yield break statement causes the enumeration to stop  In effect  yield break completes the enumeration without returning any additional items   Consider that there are actually two ways that an iterator method could stop iterating  In one case  the logic of the method could naturally exit the method after returning all the items  Here is an example   IEnumerable lt uint gt  FindPrimes uint startAt  uint maxCount        for  var i   0UL  i  lt  maxCount  i                  startAt   NextPrime startAt           yield return startAt             Debug WriteLine  All the primes were found         In the above example  the iterator method will naturally stop executing once maxCount primes have been found   The yield break statement is another way for the iterator to cease enumerating  It is a way to break out of the enumeration early  Here is the same method as above  This time  the method has a limit on the amount of time that the method can execute    IEnumerable lt uint gt  FindPrimes uint startAt  uint maxCount  int maxMinutes        var sw   System Diagnostics Stopwatch StartNew        for  var i   0UL  i  lt  maxCount  i                  startAt   NextPrime startAt           yield return startAt           if  sw Elapsed TotalMinutes  gt  maxMinutes              yield break             Debug WriteLine  All the primes were found         Notice the call to yield break  In effect  it is exiting the enumeration early   Notice too that the yield break works differently than just a plain break  In the above example  yield break exits the method without making the call to Debug WriteLine

User · Answer

Ends an iterator block  e g  says there are no more elements in the IEnumerable

User · Answer

yield break is just a way of saying return for the last time and don t return any value  e g     returns 1 2 3 4 5 IEnumerable lt int gt  CountToFive         yield return 1      yield return 2      yield return 3      yield return 4      yield return 5      yield break      yield return 6      yield return 7      yield return 8      yield return 9

User · Answer

yield break is just a way of saying return for the last time and don t return any value  e g     returns 1 2 3 4 5 IEnumerable lt int gt  CountToFive         yield return 1      yield return 2      yield return 3      yield return 4      yield return 5      yield break      yield return 6      yield return 7      yield return 8      yield return 9

User · Answer

yield basically makes an IEnumerable lt T gt  method behave similarly to a cooperatively  as opposed to preemptively  scheduled thread   yield return is like a thread calling a  schedule  or  sleep  function to give up control of the CPU   Just like a thread  the IEnumerable lt T gt  method regains controls at the point immediately afterward  with all local variables having the same values as they had before control was given up   yield break is like a thread reaching the end of its function and terminating   People talk about a  state machine   but a state machine is all a  thread  really is   A thread has some state  I e  values of local variables   and each time it is scheduled it takes some action s  in order to reach a new state   The key point about yield is that  unlike the operating system threads we re used to  the code that uses it is frozen in time until the iteration is manually advanced or terminated

User · Answer

Ends an iterator block  e g  says there are no more elements in the IEnumerable

User · Answer

It specifies that an iterator has come to an end  You can think of yield break as a return statement which does not return a value   For example  if you define a function as an iterator  the body of the function may look like this   for  int i   0  i  lt  5  i          yield return i     Console Out WriteLine  You will see me      Note that after the loop has completed all its cycles  the last line gets executed and you will see the message in your console app   Or like this with yield break   int i   0  while  true        if  i  lt  5                yield return i            else                  note that i   will not be executed after this         yield break            i       Console Out WriteLine  Won t see me      In this case the last statement is never executed because we left the function early

User · Answer

Tells the iterator that it s reached the end   As an example   public interface INode       IEnumerable lt Node gt  GetChildren       public class NodeWithTenChildren   INode       private Node   m children   new Node 10        public IEnumerable lt Node gt  GetChildren                 for  int n   0  n  lt  10    n                         yield return m children  n                       public class NodeWithNoChildren   INode       public IEnumerable lt Node gt  GetChildren                 yield break

User · Answer

It specifies that an iterator has come to an end  You can think of yield break as a return statement which does not return a value   For example  if you define a function as an iterator  the body of the function may look like this   for  int i   0  i  lt  5  i          yield return i     Console Out WriteLine  You will see me      Note that after the loop has completed all its cycles  the last line gets executed and you will see the message in your console app   Or like this with yield break   int i   0  while  true        if  i  lt  5                yield return i            else                  note that i   will not be executed after this         yield break            i       Console Out WriteLine  Won t see me      In this case the last statement is never executed because we left the function early

User · Answer

Tells the iterator that it s reached the end   As an example   public interface INode       IEnumerable lt Node gt  GetChildren       public class NodeWithTenChildren   INode       private Node   m children   new Node 10        public IEnumerable lt Node gt  GetChildren                 for  int n   0  n  lt  10    n                         yield return m children  n                       public class NodeWithNoChildren   INode       public IEnumerable lt Node gt  GetChildren                 yield break

User · Answer

Tells the iterator that it s reached the end   As an example   public interface INode       IEnumerable lt Node gt  GetChildren       public class NodeWithTenChildren   INode       private Node   m children   new Node 10        public IEnumerable lt Node gt  GetChildren                 for  int n   0  n  lt  10    n                         yield return m children  n                       public class NodeWithNoChildren   INode       public IEnumerable lt Node gt  GetChildren                 yield break

User · Answer

Ends an iterator block  e g  says there are no more elements in the IEnumerable

User · Answer

The yield keyword is used together with the return keyword to provide a value to the enumerator object  yield return specifies the value  or values  returned  When the yield return statement is reached  the current location is stored  Execution is restarted from this location the next time the iterator is called   To explain the meaning using an example        public IEnumerable lt int gt  SampleNumbers                 int counter   0          yield return counter           counter   counter   2           yield return counter           counter   counter   3           yield return counter            Values returned when this is iterated are  0  2  5   It   s important to note that counter variable in this example is a local variable  After the second iteration which returns the value of 2  third iteration starts from where it left before  while preserving the previous value of local variable named counter which was 2

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