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(((MyObject)myList[foundIndex]).ID.ToString());  ?? try to understand this

Posted on 2014-09-11
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Last Modified: 2014-09-18
Could someone explain me what these two lines mean?
     int foundIndex = myList.BinarySearch(new MyObject() { ID = 4 });

       Debug.WriteLine(((MyObject)myList[foundIndex]).ID.ToString());


 ArrayList myList = new ArrayList();
            myList.Add(new MyObject() { ID = 2 });


            myList.Add(new MyObject() { ID = 4 });
            myList.Add(new MyObject() { ID = 6 });
            myList.Add(new MyObject() { ID = 10 });
            myList.Sort();

            //foreach (MyObject i in myList)
            //{
              //  Debug.WriteLine(i.ID.ToString());
            //}
            int foundIndex = myList.BinarySearch(new MyObject() { ID = 4 });
            if (foundIndex >= 0)
            {
                Debug.WriteLine(((MyObject)myList[foundIndex]).ID.ToString());

            }
            else
            {
                Debug.WriteLine("element not found");
            }

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Question by:yguyon28
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Jeff Tennessen earned 500 total points
ID: 40317317
The first line is doing a binary search against the list. A binary search is an algorithm for searching a sorted list much faster than a standard linear search. In this case, it is searching the list for the instance of "MyObject" whose ID property is 4. If it finds it, it stores the object's position within the list in the variable "foundIndex."

The second line writes the value of the ID property out to the debugging console. This appears to be simply a way of ensuring that the object with ID 4 was, indeed, found. To break it down, "myList[foundIndex]" gets the item from the list that resides at the position indicated by foundIndex. This item is then cast as type MyObject: "((MyObject)myList[foundIndex])". Finally, it gets the value of the ID property from the cast item and converts it to a string for writing to the debugging console. (Technically, the .ToString() method is unnecessary here, as Debug.WriteLine() will call ToString() itself for any object passed to it.)

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