ora-12541 when connecting to oracle db

Pls, check my codes. I added app.config file into project. codes are

<configuration>
<connectionStrings>
<add name ="SQLConnection" providerName="Oracle.DataAccess.Client"
connectionString="Data Source=localhost:1521/orcl; user id=scott; password=tiger"/>
</connectionStrings>
</configuration>

In C++/CLI file I tried to connect Oracle DB but failed. Codes are like below

#include "stdafx.h"

using namespace System;
using namespace System::Data;
using namespace System::Data::Common;
using namespace System::Configuration;
using namespace Oracle::DataAccess::Client;

int main(array<System::String ^> ^args)
{
try{
String^ provider = ConfigurationManager::ConnectionStrings["SQLConnection"]->ProviderName;
DbProviderFactory^ factory = DbProviderFactories::GetFactory(provider);
DbConnection^ conn = factory->CreateConnection();

String^ connection = ConfigurationManager::ConnectionStrings["SQLConnection"]->ConnectionString;
conn->ConnectionString = connection;
conn->Open(); //Exception Occurs!

}
catch (Exception^ e) {
Console::WriteLine(e->Message);
}
return 0;
}

Exception is ora-12541 No Listener. But "tnsping orcl" is done well. and I executed "lsnrctl start".

I need your advice. Thanks in advance.

Best Regards.