SqlConnection Error con.Open()

 using UnityEngine;
 using System.Collections;
 using System.Data.SqlClient;
 public class Deneme : MonoBehaviour {
     // Use this for initialization
     void Start () {
     }
     // Update is called once per frame
     void Update () {
     }
     void OnGUI()
     {
         if(GUILayout.Button("Baglan"))
         {
             SqlConnection con = new SqlConnection(@"Server=localhost;Database=deneme;Trusted_Connection=True;");
             con.Open();
         }
     }
 }

Help me. this not running. SocketExcaption : no connection could be made because the target machine actively refused it