Manually increment an enumerator inside foreach loop

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情话喂你
情话喂你 2021-01-18 06:20

I have a nested while loop inside a foreach loop where I would like to advance the enumerator indefinitately while a certain condition is met. To do this I try casting the e

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  •  轮回少年
    2021-01-18 07:16

    Many of the other answers recommend using continue, which may very well help you do what you need to do. However, in the interests of showing manually moving the enumerator, first you must have the enumerator, and that means writing your loop as a while.

    using (var enumerator = times.GetEnumerator())
    {
        DateTime time;
        while (enumerator.MoveNext()) 
        {
            time = enumerator.Current;
            // pre-condition code
            while (condition)
            {
                if (enumerator.MoveNext())
                {
                    time = enumerator.Current;
                    // condition code
                }
                else 
                {
                    condition = false;
                }
            }
            // post-condition code
        }
    }
    

    From your comments:

    How can the foreach loop advance it if it doesn't implement the IEnumerator interface?

    In your loop, time is a DateTime. It is not the object that needs to implement an interface or pattern to work in the loop. times is a sequence of DateTime values, it is the one that must implement the enumerable pattern. This is generally fulfilled by implementing the IEnumerable and IEnumerable interfaces, which simply require T GetEnumerator() and object GetEnumerator() methods. The methods return an object implementing IEnumerator and IEnumerator, which define a bool MoveNext() method and a T or object Current property. But time cannot be cast to IEnumerator, because it is no such thing, and neither is the times sequence.

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