Why can't the elements of the list be ref?

명관 송 21 Reputation points
2022-04-20T06:35:33.047+00:00

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C#
C#
An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
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  1. Jack J Jun 24,496 Reputation points Microsoft Vendor
    2022-04-20T09:29:47.18+00:00

    @명관 송 , based on my test, I reproduced your problem.

    According to the Microsoft doc ref said, An argument that is passed to a ref or in parameter must be initialized before it is passed.

    Therfore, we could use the following code to initialize the argument.

      public static void GetSuffleList<T>(ref List<T>_list)  
            {  
                for (int i = 0; i < _list.Count; i++)  
                {  
                    Random random = new Random();  
                    int rnd = random.Next(0, i);  
                    T t1= _list[i];  
                    T t2= _list[rnd];  
                    Swap(ref t1 ,ref t2);  
      
                }  
            }  
       
    

    Hope this coudl help you.

    Best Regards,
    Jack


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  1. Bruce (SqlWork.com) 61,416 Reputation points
    2022-04-20T15:19:23.06+00:00

    Pass by ref means you pass the address of the variable, rather than the address of the value. But indexing into an array is really method that return a value, not a variable.

    As suggested above you could copy the indexed values to variable, but calling your swap would swap the values in variables not the list.

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