Why Does My C# Code Produce a 'Not All Code Paths Return a Value' Error?

C# compiler problem: all code paths returned by processing value

When trying to determine whether the given integer can be removed by each number between 1 and 20, the developer encounters an error message that the content is "not all code paths return values."

Code check

After checking the following code, the compiler error is obvious:

The problem comes from only two Return statements in the function body. These statements do not be removed or can be removed by all numbers between 1 and 20. However, the compiler requires all possible execution paths in the function to return the value.

{
    for(int j = 1; j <= 20; j++)
    {
        if(num % j != 0)
        {
            return false;
        }
        else if(num % j == 0 && num == 20)
        {
            return true;
        }
    }
}

Solution

In order to solve this error, you need to add another RETURN statement to the code to handle the remaining execution paths. This path indicates that the cycle is completed and no number of numbers that can be removed from 1 to 20 can be found.

The following code contains the lack of RETURN statements to ensure that all possible code paths are now returned:

The improved solution description:

{
    for(int j = 1; j <= 20; j++)
    {
        if(num % j != 0)
        {
            return false;
        }
        else if(num % j == 0 && num == 20)
        {
            return true;
        }
    }

    return true;  //添加了缺少的 return 语句,  此处应为true，表示可以被1-20整除
}

in the original code is too strict. Only when

is equal to 20 and can be returned when it is removed at the same time. If is the multiple of 20 but greater than 20, the code will not return any value. Therefore, the correct code should return by default after the cycle is over, indicating that the number can be removed by each number between 1 to 20. else if(num % j == 0 && num == 20) is returned only when the cycle is found in the cycle. num

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