Can not establish connection with the sql server

Question

When I am trying to move data from Dictionary to DB, I can't even establish a connection. This is the code of the function:

                const string serverName = @"homer";
                const string database = "RealState_RiskEngine";
                const string databaseTable = "dbo.LDR_ACCOUNT_DATA";

                Dictionary<string, Dictionary<string, string>> aliasesAndDatesAndValues = dictionary;
                string strCon = string.Format("Data Source={0}\\SQLSTANDARD;Initial Catalog={1};Integrated Security=SSPI",
                    serverName, database);
                SqlConnection conn = new SqlConnection(strCon);
                conn.Open();

                string SQLstr = string.Format("INSERT INTO {0} (ID_ACCOUNT, DATE_TRIMESTER, VALUE)" +
                   "VALUES ('@ID_ACCOUNT', '@DATE_TRIMESTER', '@VALUE')", databaseTable);
                SqlCommand cmd = new SqlCommand(SQLstr, conn);
                cmd.Parameters.Add("@ID_ACCOUNT", System.Data.SqlDbType.VarChar);
                cmd.Parameters.Add("@DATE_TRIMESTER", System.Data.SqlDbType.Date);
                cmd.Parameters.Add("@VALUE", System.Data.SqlDbType.Int);


                foreach (var pair in aliasesAndDatesAndValues)
                {
                    foreach (var internal_pair in pair.Value)
                    {
                        cmd.Parameters["@ID_ACCOUNT"].Value = pair.Key.ToString();
                        DateTime dateAndTime = Convert.ToDateTime(internal_pair.Key.ToString());
                        var date = dateAndTime.Date;
                        Console.WriteLine(date);
                        Console.ReadLine();

                        cmd.Parameters["@DATE_TRIMESTER"].Value = date;
                        cmd.Parameters["@VALUE"].Value = int.Parse(internal_pair.Value);
                        cmd.ExecuteNonQuery();
                    }
                }

If I have SqlConnection without parameter, I get this stack trace:

System.InvalidOperationException: The ConnectionString property has not been initialized.
   at System.Data.SqlClient.SqlConnection.PermissionDemand()
   at System.Data.SqlClient.SqlConnectionFactory.PermissionDemand(DbConnection outerConnection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at ConsoleApplication2.Program.fillUpLdrAccounData(Dictionary`2 dictionary) in c:\users\atsurkanu\documents\visual studio 2015\Projects\ConsoleApplication2\ConsoleApplication2\Program.cs:line 354

And if I have SQLConnection with parameter (SqlConnection conn = new SqlConnection(strCon)), than I get this one stack trace:

at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at ConsoleApplication2.Program.fillUpLdrAccounData(Dictionary`2 dictionary) in c:\users\atsurkanu\documents\visual studio 2015\Projects\ConsoleApplication2\ConsoleApplication2\Program.cs:line 354
ClientConnectionId:00000000-0000-0000-0000-000000000000
Error Number:-1,State:0,Class:20

Answer 1

It was a problem with this one:

SqlConnection conn = new SqlConnection(strCon);

In my case, it should be like this one:

SqlConnection conn = new SqlConnection("Server = name; Database = DBname; Integrated Security = True;");