WCF Fbconnection Error

Mistake allows at parameter fbcon.

In another unit same mistake. Unit:
public int CreateQueue(string queueName)
{
FbConnection fbcon = new FbConnection(OpenConnection());
int i=3;
crQueue.CommandType = CommandType.Text;
crQueue.CommandText = "insert into queue values (@id,@name,@current_status_id)";
crQueue.Parameters.Add("@id", FbDbType.Numeric).Value =5; crQueue.Parameters.Add("@name", FbDbType.VarChar).Value = queueName; crQueue.Parameters.Add("@current_status_id",FbDbType.Numeric).Value=i++; crQueue.Connection = fbcon;
fbcon.Open();
crQueue.ExecuteNonQuery();
return 1;
}

In openconnection function i have code like this:

public string OpenConnection()
{
//string res;
//FbConnectionStringBuilder fb_con = new FbConnectionStringBuilder();
//fb_con.Charset = Charset;
//fb_con.Database = LogonDatabase;
//fb_con.UserID = User;
//fb_con.Password = Password;
//fb_con.ServerType = 0;

string strConnect = "User=" + User + ";Password=" + Password + ";Database=" + LogonDatabase + ";DataSource="+Server+"; Port=3050;" +
"Dialect=" + Dialect + "; Charset=" + Charset + ";Role=;Connection lifetime=15;Pooling=true; MinPoolSize=0;MaxPoolSize=50;"+
"Packet Size=8192;ServerType=0;";
//FbConnection fbcon = new FbConnection(strConnect);
//fbcon.ConnectionString = strConnect;
//fbcon.Open();
//if (fbcon.State == ConnectionState.Open)
//{res = true;
//fbcon.Close();}
//else
//{res = false;
// fbcon.Close();}
return strConnect;
}

The variables User,Password and others i take from global variables

public string strConnect;
public string User = ConfigurationManager.AppSettings["User"];
public string Password = ConfigurationManager.AppSettings["Password"];
public string LogonDatabase = ConfigurationManager.AppSettings["LogonDatabase"];
public string Server = ConfigurationManager.AppSettings["Server"];
public string Charset = ConfigurationManager.AppSettings["Charset"];
public string Dialect = ConfigurationManager.AppSettings["Dialect"];

of config file App.config