How to Remove Duplicate Items From a Combo Box in C#

I was attempting to write code to remove duplicate items either before they are written to the combobox selection, or removing them once they have been added to the collection so that only one instance of each type of Credit Card Description will appear. I have attached my code that I was attempting to use to complete this task, and i am failing to see where I am "missing the connection" as to why I am unable to successfully remove duplicate items or stop them from being input. Please reference the attached code, or please feel free to give your own example of code on how to loop through all of the elements of a combo box and be able to remove the items from there.

private bool CCDescription_Duplicate(int position)
        {
            //Declare Local Variables
           // bool found = false;
            int counter = 0;
            string temp = "";

            if (comboBox1.Items.Count > 2)
            {
                //temp = comboBox1.Items[comboBox1.Items.Count - 2].ToString();
                while (counter < comboBox1.Items.Count - 1)
                {
                    //if (comboBox1.Items[comboBox1.Items.Count-1] == comboBox1.Items[counter])
                    if(thirdPartyCOM[position] == comboBox1.Items[counter])
                    {
                        return true;
                    }//end if

                    else
                        counter++;

                }//end while
            }//end if

            else if (comboBox1.Items.Count == 2)
            {
                if (comboBox1.Items[0] == thirdPartyCOM[position] || comboBox1.Items[1] == thirdPartyCOM[position])
                    return true;
                //if (comboBox1.Items[0] == comboBox1.Items[1])
                //    return true;
            }//end else if

            else
                return false;
            
            return false;


        }//end CCDescription_Duplicate

Select allOpen in new window