C#如何添加对数据是否存在的判断？

如题，想在if中再添加一个if语句，如果workerNo存在，无法提交；不存在，则添加成功

if (workerName != string.Empty && workerSex != string.Empty && workerNo != string.Empty && workerGroup != string.Empty && workerType != string.Empty && workerStatus != string.Empty)
            {
                
                string insertform = "INSERT INTO hr_workerinfo(workerName,workerSex,workerNo,workerGroup,workerType,createTime,updateTime,workerStatus)" +
                               "values ('{0}','{1}','{2}','{3}','{4}','{5}','{6}','{7}')";
                string insertsql = String.Format(insertform, workerName, workerSex, workerNo, workerGroup, workerType, createTime, updateTime, workerStatus);
                commonEntity.mysqlComExecute(insertsql);
                MessageBox.Show("添加成功！", "Tip", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
            else
            {
                MessageBox.Show("提交信息不完整！", "Tip", MessageBoxButtons.OK, MessageBoxIcon.Stop);
            }

merge into hr_workerinfo t
using (select '{0}'   as workerNo from dual) tmp
on (tmp.workerNo = t.workerNo)
when not matched then
  insert (.. .) values (.. .)