winform批量查询单号剔除重复

//查询分单函数
        private string GetQueryInSubbillNo()
        {
            string strSubbillNO = "";
            string strOutput = "";
            foreach (DataGridViewRow dgvRow in dgvRecieveProducts.Rows)
            {
                strSubbillNO += "'" + dgvRow.Cells["dgvSubbillNO"].Value.ToString() + "',";
            }
            if (dgvRecieveProducts.Rows.Count > 0)
            {
                string strinput = strAddSubbillNo + strSubbillNO.Substring(0, strSubbillNO.Length - 1);
                Array stringArray = strinput.Split(',');
                List<string> listString = new List<string>();
                //遍历删除重复项
                foreach (string eachString in stringArray)
                {
                    if (!listString.Contains(eachString)) //确定是否存在，存在跳过
                        listString.Add(eachString);
                }
                foreach (string subbillNo in listString)   //筛选值
                {
                    strOutput += subbillNo + ",";
                }
                return strOutput.Substring(0, strOutput.Length - 1);
            }
            else { return ""; }
        }