Question

List<string> Getlist()
{
    List<string> mylist;
    for (bool successFlag = false; !successFlag; )  //It will definitely enter the loop once.
    {
        successFlag = true;
        mylist = new List<string>();
        for (int i = 0; i < n; i++)
        {
            var CDF = GetCDF(); // IEnumerable, each call of GetCDF() gives different result
            if (!CDF.Any())
            {
                fail++;
                successFlag = false;
                break;
            }
            string item = GetNext(CDF);
            mylist.Add(item);
        }
    }
    return mylist; // Here IDE poses an error
}

I guess there is a way to recursively use Getlist() instead of do a for loop and flag retry, maybe some kind of immutable method?

i dont wanna initiate the list outside the loop because i would like to discard the list when successFlag is false;

Discard simply means when successFlag = false, then mylist.removeall. And then start everything over again as fresh, so I am asking for an approach to recursively call GetList() instead of clear the states in the method

Update

do while works!

Answer 1

The issue has to do with this line. If it doesn’t run you List would never be initialized.

for (bool successFlag = true; !successFlag; )

Now if you change your code to this it should work fine.

    List<string> Getlist()
    {
        List<string> mylist= new List<string>();
        for (bool successFlag = true; !successFlag; )
        {
            for (int i = 0; i < n; i++)
            {
                var CDF = GetCDF(); // IEnumerable
                if (!CDF.Any())
                {
                    fail++;
                    successFlag = false;
                    break;
                }
                string item = GetNext(CDF);
                mylist.Add(item);
            }
        }
        return mylist;
    }

Update :

Run untill GetCDF(); is not empty. This can cause an infinite loop if GetCDF() is always empty!!!

List<string> Getlist()
{
    List<string> mylist= new List<string>();
    for (int i = 0; i < n; i++)
    {
        var CDF = GetCDF(); // IEnumerable
        if (!CDF.Any())
        {
                        Thread.Sleep(1000); //Sleep for 1 second.   
            fail++;
            return Getlist();
        }
        string item = GetNext(CDF);
        mylist.Add(item);
    }

    return mylist;
}