Need help converting this snippet from c to c#

Question

typedef struct {
    int e1;
    int e2;
    int e3;
    int e4;
    int e5;
} abc;


void Hello(abc * a, int index)
{
    int * post = (&(a->e1) + index);

    int i;
    for(i = 0; i<5; i++)
    {
        *(post + i) = i;    
    }
}

The problem I face here is how they able to access the next element in the struct by

*(post + i)

I'm not sure how all these would be done in C# and moreover, I don't want to use unsafe pointers in C#, but something alternate to it.

Thanks!

Answer 1

You should replace the struct with an array of 5 elements.

If you want to, you can wrap the array in a class with five properties.

edit...

When you say 'Wrap,' it generally means to write properties in a class that set or get the value of either a single variable, an array element, or a member of another class whose instance lives inside your class (the usual usage here = 'wrap an object'). Very useful for separating concerns and joining functionality of multiple objects. Technically, all simple properties just 'wrap' their private member variables.

Sample per comment:

class test
{

    int[] e = new int[5];
    public void Hello(int index)
    {
        for (int i = 0; i <= 4; i++) {
            // will always happen if index != 0
            if (i + index > 4) {
                MsgBox("Original code would have overwritten memory. .Net will now blow up.");
            }
            e[i + index] = i;
        }
    }

    public int e1 {
        get { return e[0]; }
        set { e[0] = value; }
    }

    public int e2 {
        get { return e[1]; }
        set { e[1] = value; }
    }

    //' ETC etc etc with e3-e5 ...

}

Answer 2

The problem with the C code is that if index is greater than 0 it runs off the end of the abc struct, thus overwriting random memory. This is exactly why C#, a safer language, does not allow these sorts of things. The way I'd implement your code in C# would be:

struct abc
{
    public int[] e;
}

void Hello(ref abc a, int index)
{
    a.e = new int[5];
    for (int i = 0;  i < 5;  ++i)
        a.e[index + i] = i;
}

Note that if index > 0, you'll get an out of bounds exception instead of possibly silent memory overwriting as you would in the C snippet.