How not add new data into database that has similar id with data in database?

Question

So I am making a Project a in Windows Forms and what I have to do is to get data from Excel and display it in Datagridview. I am Uploading data on Sql Server and than I am sending it in DVG.Every Time I Upload data on Server I have to add new data to old data but I does not have datas in database with similar id. I have Code to add new data in sql Server but I donn't know how not to add new data, that have a similar id with data in sql. Has anyone idea how t do that ? Here is my Code:

SqlBulkCopy oSqlBulk = null;

            string excelFilePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
            excelFilePath = Path.Combine(excelFilePath, label1.Text);
            OleDbConnection excelConn = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + excelFilePath + ";Extended Properties=Excel 12.0;");

            try
            {
                excelConn.Open();
                OleDbCommand excelComm = new OleDbCommand("SELECT *FROM [Sheet1$]", excelConn);

                OleDbDataReader excelreader = excelComm.ExecuteReader();

                using(SqlConnection con = new SqlConnection("Data Source=DESKTOP-OETHK6U\\SQLEXPRESS;Initial Catalog=Intel_DB;Integrated Security=True"))
                {
                    con.Open();
                    oSqlBulk = new SqlBulkCopy(con);
                    oSqlBulk.DestinationTableName = "Intel_Data";
                    oSqlBulk.WriteToServer(excelreader);
                }
                label2.Text = "Data has been added into database";
            }
            catch(Exception ex)
            {
                label2.Text = "Data has not been added into database";
                MessageBox.Show(ex.Message);
            }
            finally
            {
                oSqlBulk.Close();
                oSqlBulk = null;
                excelConn.Close();
                excelConn = null;
            }

Answer 1

Try this

if (not exists(select * from table where ID= @id))
insert into table(fields) values (values)

or you can set unique constraint in ID so if user add same id it will throw error where you have handle it..