SQL connection Problem

Hi guys. I need some help please. I tried make an INSERT into my SQLDB but i cant because give me an error in this code line:

"commandoSQL.Connection = dbcon;"

the system send me this mensage:

"Assets/NGUI/Scripts/Interaction/ChamarVariavel.cs(43,29): error CS0266: Cannot implicitly convert type System.Data.IDbConnection' to System.Data.SqlClient.SqlConnection'. An explicit conversion exists (are you missing a cast?)"

I hope somebody can help me with this. Thanks

 public class ChamarVariavel : MonoBehaviour {
 
     public UISlider slider;
 
     // Use this for initialization
     void Start () {
     }
 
     // Update is called once per frame
     void Update () {
     }
 
     void OnGUI(){
         // Connection DB
         string connectionString = "Data Source=(local);Initial Catalog=Test;User ID=******;Password=*******";
 
         IDbConnection dbcon;
 
         dbcon= new SqlConnection(connectionString);
 
         dbcon.Open();
         //DB Online
 
         float x = slider.value * 100;
         GUI.Label(new Rect( 570, 238, 70, 30 ), "(" + x.ToString("f2") + ")");
 
         string qInsert = string.Format(@"INSERT INTO Fuel (fuel) VALUES ('{0}')", x);
 
         SqlCommand commandoSQL = new SqlCommand(qInsert);
 
         commandoSQL.Connection = dbcon;
 
         try
         {
             commandoSQL.ExecuteNonQuery();
         }
         catch (Exception ex)
         {
             GUI.Label(new Rect( 300, 40, 300, 300 ), ex.ToString());
         }
 
         dbcon.Close();
         //DB offline
     }
 }