Update if Exists Else Insert

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Collections; 

namespace Dispatch_Tracker
{
    public partial class DispatchTracker : Form
    {
        public DispatchTracker()
        {
            InitializeComponent();
        }

    string connection = "Data Source=WN7-4WVX1BS;" + "Initial Catalog=DispatchDB;Persist Security Info=True;" + "User ID=sa;" + "Password= ***";

        private void Save_Click(object sender, EventArgs e)
        {
            if (DispatcherName.Text == "")
            {
                MessageBox.Show("Would you like to Lose out on Productivity?\nPlease select the Dispatcher name.");
                DispatcherName.Focus();
            }

            else if (DispatchNumber.Text == "")
            {
                MessageBox.Show("Did you really process a Dispatch?\nI don't see a Dispatch Number.");
                DispatchNumber.Focus();
            }

            else if (DPSType.Text == "")
            {
                MessageBox.Show("Did You Just Forget Something?\nPlease Enter the DPS Type");
                DPSType.Focus();
            }

            else if (QG.Text == "")
            {
                MessageBox.Show("Please select the Queue which the DPS belongs to.");
                QG.Focus();
            }
           
            else
            {
                dateTimePickerDT.Value = System.DateTime.Now;
                string sDispatcher = DispatcherName.Text;
                string sDPSNum = DispatchNumber.Text;
                string sDPSType = DPSType.Text;
                DateTime dtDT = dateTimePickerDT.Value;
                string sQueue = QG.Text;

                string query = "INSERT INTO dps_data(DispatcherName, DispatchNumber, DPSType, DateTime, Queue)" +"VALUES( @Dispatcher, @DPSNum, @DPSType, @DT, @Queue)";

                SqlConnection conn = new SqlConnection(connection);
                SqlCommand cmd = new SqlCommand(query, conn);
                conn.Open();

                cmd.Parameters.Add(new SqlParameter("@Dispatcher", sDispatcher));
                cmd.Parameters.Add(new SqlParameter("@DPSNum", sDPSNum));
                cmd.Parameters.Add(new SqlParameter("@DPSType", sDPSType));
                cmd.Parameters.Add(new SqlParameter("@DT", dtDT));
                cmd.Parameters.Add(new SqlParameter("@Queue", sQueue));

                int result = cmd.ExecuteNonQuery();
    
                if (result > 0)
                
                {
                    MessageBox.Show("Data Added Successfully");
                }
                
                else
                    
                {
                    MessageBox.Show("Error in Adding Data");
                }

                conn.Close();

                DispatchNumber.Text = String.Empty;
                DPSType.Text = String.Empty;
                QG.Text = String.Empty;
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void DispatcherName_SelectedIndexChanged(object sender, EventArgs e)
        {

        }

        private void QG_SelectedIndexChanged(object sender, EventArgs e)
        {
            
        }
       
    }
}