Develop Reference

Can't connect to database in vb.net

Keeps throwing the exception:
An unhandled exception of type 'System.InvalidOperationException'
occurred in MySql.Data.dll
here is the code:
Public Sub showWorkerFullnames()
getQuery = "SELECT worker.worker_fullname FROM worker"
getCommand = New MySqlCommand(getQuery, MySQLConnection)
getReader = getCommand.ExecuteReader
cbWorkerFullnames.Items.Clear()
While getReader.Read
cbWorkerFullnames.Items.Add(getReader.Item("worker_fullname").ToString)
End While

This page shows a working example.
Creating a connection:
string connStr =
"server=localhost;user=root;database=world;port=3306;password=******;";
MySqlConnection conn = new MySqlConnection(connStr);
Use that connection object when creating the command:
MySqlCommand cmd = new MySqlCommand(sql, conn);
Open the connection before using it. The linked example opens the connection right after creating it. It's hair-splitting, but I would make opening the connection the very last thing before using it.
conn.Open();
And don't forget to close the connection when you're done.

Open database into application c#

I have added a SQL Server .mdf database file to my C# application, but when I try to connect with this code, the program causes a connection error.
CODE:
DataSet data;
string con = "Data Source=dbinterno.mdf;";
string queryString = "Select * FROM Dati";
try
{
using (SqlConnection connection = new SqlConnection(con))
{
connection.Open();
SqlDataAdapter adapter = new SqlDataAdapter();
SqlCommand command = new SqlCommand(queryString, connection);
command.ExecuteNonQuery();
data = new DataSet();
adapter.Fill(data);
MessageBox.Show(data.ToString());
connection.Close();
}
}
catch
{
MessageBox.Show("\n Problemi di connessione al database");
}
The error is:
ERROR IMAGE

Here are a couple observations:
Your connection string will need to be modified. Try using
string con = "Server=myServerAddress;Database=myDataBase;Trusted_Connection=True;";
using Windows Authentication or this:
string con = "Server=myServerAddress;Database=myDataBase;User Id=myUsername;
Password=myPassword;"; using standard security, Source: connectionstrings.com. This should be managed some other way than in code as well. Desktop applications can be de-compiled, and if the password changes, you would need a rebuild. In a ASP.NET application, Microsoft advises to use a web.config file or in the windows registry using a custom subkey.
You will want to use ExecuteReader() for a SELECT statement as ExecuteNonQuery() will not return a result set. See this answer that describes the differences in the types of SQL Server methods
you don't need connection.Close();, the using statement will handle that.

Additional information: Connection error: Trying to add unknown port '192.168.1.100'

static void Main(string[] args)
{
OleDbConnection conn = new OleDbConnection("Provider=SAOLEDB.10;LINKS=tcpip(IP=192.168.1.100,Port=2638);ENG=dental;Persist Security Info = True; User ID = dba; PWD = sql");
conn.Open();
OleDbCommand cmd = new OleDbCommand("SELECT tran_num FROM transactions WHERE tran_date > '2015-10-01'", conn);
OleDbDataReader reader = cmd.ExecuteReader();
while (reader.Read())
{
Console.WriteLine("{0}", reader.GetValue(0).ToString());
}
reader.Close();
conn.Close();
if (Debugger.IsAttached)
{
Console.ReadLine();
}
}
As the title suggests, I'm getting an error when attempting to connect to this server. The driver (Provider) works fine for a local database using the same server setup, trying to adjust the code to connect remotely to the same setup at a different location. This is an old SQL Anywhere 10 database and I've tried hard to find answers for this with no success so far.
Edit: I changed the string a little to reflect some suggestions, now just getting a new error: Additional information: Connection error: TCPIP requires a server name
Update: The syntax changes to LINKS seems to have progressed my attempts but now I'm having issues with the syntax it's looking for when searching for a server at that IP. Receiving an error: Additional information: Database server not found
This is the connection string in registry:
DBN=DENTSERV;DSN=DENTAL;UID=DBA;PWD=SQL
I've tried both ServerName= and ENG= using the DSN and DBN, also while having them in ' ' but still receiving that same error. Any thoughts?

An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll

I get that error when I try to debug my program. Searched for this error but could not really figure it out on my own. Also when I try to connect my database I get this error "error: 26 - Error Locating Server/Instance Specified".
public DataTable ReadData(string st_proc, SqlParameter[] param)
{
SqlCommand command = new SqlCommand();
command.CommandType = CommandType.StoredProcedure;
command.CommandText = st_proc;
command.Connection = conn;
if (param != null)
{
command.Parameters.AddRange(param);
}
SqlDataAdapter db = new SqlDataAdapter(command);
DataTable dt = new DataTable();
db.Fill(dt);
return dt;
}

Looks like you have got the connection string from some else's machine. Here Data Source=(Localdb)\mssqllocaldb; means it is pointing to "[Sql Server Express LocalDB 2014][1]".
Make sure you have it installed on you machine. You can also try connecting to DataSource=(Localdb)\v11.0; which is "Sql server express 2012" and use it in your connection string. See if this works.

Can't connect to database (OCIenVCreate has failed)

I'm using an Oracle database(10g) which contains a stored procedure called Foo.
Foo takes 2 datetime as IN parameters and 1 cursor as OUT parameter. I've been trying to make the connection and the query to the database with the OleDbCommand, but since Foo needs a cursor I have no choice but to use a OracleCommand(right?).
When I try to connection to the database I get the following error : "OCIenvCreate has failed return code -1". I've gived the correct permissions to ASPNET user for the oci.dll file so that it can read and execute it. Unfortunately, I still get the same error and I'm lost.
Here is what cause the error
OracleConnectionStringBuilder conBuilder = new OracleConnectionStringBuilder();
conBuilder.DataSource = dataSrc;
conBuilder.UserID = user;
conBuilder.Password = password;
OracleConnection con = new OracleConnection(conBuilder.ConnectionString);
OracleCommand cmd = new OracleCommand("foo", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("this_is_a_cursor", OracleType.Cursor).Direction = ParameterDirection.Output;
con.Open(); // Cause the error at runtime
OracleDataReader reader = cmd.ExecuteReader();
GridView1.DataSource = reader;
GridView1.DataBind();
con.Close();
I've noticed that some other people are having the same problem.
I'm running the application from a Windows Server 2003 Entreprise Edition(I hope this can help).
Thank you.

I'm not quite sure what the exact problem was, but I managed to connect to my database with another provider in the connection string.