Yield (C # reference)

The iterator block is used to provide a value to the enumerated number object or send an iteration end signal. It is in the form of one of the following:

YieldReturn <expression>;YieldBreak;

Remarks

Calculates the expression and returns it as an enumerated number object value;ExpressionIt must be implicitly converted to an iteratorYieldType.

YieldThe statement can only appear inIteratorBlock. These methods, operators, or accessors are subject to the following constraints:

• Insecure blocks are not allowed.

• The parameters of methods, operators, or accessors cannot be ref or out.

YieldThe statement cannot appear in the anonymous method. For more information, see the anonymous method (C # programming guide ).

When andExpressionWhen used together,YieldReturnThe statement cannot appear inCatchBlock or contains one or moreCatchClauseTryBlock. For more information, see Exception Handling statements (C # reference ).

Example

In the following example, the iterator block (here is the methodPower (INT number, int power)).YieldStatement. WhenPowerMethod. Note:PowerThe return type of the method isIenumerable(An iterator interface type ).

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//Yield-Example. csusing system; using system. collections; public class list {public static ienumerable power (INT number, int exponent) {int counter = 0; int result = 1; while (counter ++ <exponent) {result = Result * number;YieldReturn result ;}} static void main () {// display powers of 2 up to the exponent 8: foreach (int I in power (2, 8) {console. write ("{0}", I );}}}

2 4 8 16 32 64 128 256