Compare two list C#

[Zulhilmi_1]

hye everyone i have some problem with coding. The problem is i have two data which is need to be compared for matching item and there is some of the data have duplicates and i did not want to remove the duplications, the part of the data is divided by an empty space. What i need is to compare the data symmetricaly.
The test data is like this:-

Data 1:
A

B
C
D

Data 2:
A
Q
C

B
C
D

the result suppose to be :
A is match
Q is not match
C is not match

B is match
C is match
D is match

what i get for the result is :

A is match
Q is not match
C is match

B is match
C is match
D is match

bool found = false;
            foreach (string str in list2.ToList())
            {
                foreach (string str2 in list.ToList())
                {
                   if(!str2.Equals(""))
                   {

                       if (str.Equals(str2))
                       {
                           found = true;
                           listBox1.Items.Add(str2 + " and " + str + " MATCH ");
                           break;
                       }

                   }

                   else
                   {
                       if (str.Equals(""))
                            found = false;
                   }

                }

                if (!str.Equals(""))
                {
                    if (found == false)
                    {
                        listBox1.Items.Add(str + " NOT MATCH ");
                    }
                }

                else
                    listBox1.Items.Add("");
                found = false;
            }

[Reverend Jim]

Looking at your data I interpret it as being lists of lists. Data Set 1 consists of two lists

A    
B C D

Data Set 2 consists of two lists

A Q C
B C D

So break your problem down. Instead of comparing two Data Sets you are comparing lists of lists. In pseudo code

Do until no more lists

    get list from Data Set 1
    get list from Data Set 2
    compare the lists

loop

To compare the lists you just step through both lists together (stopping when one list is exhausted) and compare elements at the same position. You can write a function that returns a list from a data set, or some value that indicates there are no more lists.