I am working with a SQL compact database and I am able to test the connection when I import it and copy the exact file path to my code, but it still says that it hasn't been opened. What am I doing wrong? Are there any shortcuts available if I have already added the database to my project?
Thanks!
Imports System.Data.SqlServerCe
Module Module1
Sub Main()
Dim constring As String = "Data Source=C:\Users\test\Desktop\MyDatabase1.sdf"
Dim conn As New SqlCeConnection(constring)
Dim cmd As New SqlCeCommand("SELECT * FROM ACCOUNT")
conn.Open()
Dim reader As SqlCeDataReader = cmd.ExecuteReader()
While reader.Read()
Console.WriteLine(reader)
End While
End Sub
End Module
You need to assign the connection to the command:
Immediately after this line:
conn.Open()
add:
cmd.Connection = conn
Alternatively, you can add the connection to the command's constructor:
Dim cmd As New SqlCeCommand("SELECT * FROM ACCOUNT", conn)
One of the main advantage of using SQL server CE (3.5) is to have Linq to SQL. You should make use of strongly typed database, and of DataContext. if you do so, then creating a new DataContext is ONE line of code, not 8. And if your DataBase file does not exist, the CreateDataTable method of your DataContext will create them for you. Dig a little into this, because using SQL Server CE like an old fashion OLEDB data provider is... well... not optimal :-)
Related
My application uses a database stored in a file available via network. So far, I've been using a MS-Access file (.accdb), but I'm trying to migrate to SQLite Version 3 (.db3).
I added SQLite NuGet package to my project and created a SQLite database using SQLiteStudio. I refactored my database objects to work with System.Data.SQLite.SQLiteConnection instead of System.Data.OleDb.OleDbConnection and it worked well.
However, my previous accdb database was password protected, and I don't know how to apply a password over my current SQLite database.
Can anyone teach me ho to do it? Thanks in advance!
I followed the link which Wudge kindly appointed in comment above, and it works, but I'd rather clarify what need to be done:
To set a password to an unprotected database:
Dim conn = New SQLite.SQLiteConnection(
"Data Source=C:\yourFolder\yourDB.db3;Version=3;")
conn.Open()
conn.ChangePassword("password")
conn.Close()
To open a password-protected database:
Dim conn = New SQLite.SQLiteConnection(
"Data Source=C:\yourFolder\yourDB.db3;Version=3;")
conn.SetPassword("password")
conn.Open()
conn.Close()
or
Dim conn = New SQLite.SQLiteConnection(
"Data Source=C:\yourFolder\yourDB.db3;Version=3;Password=password;")
conn.Open()
conn.Close()
To remove password from a password-protected database:
Dim conn = New SQLite.SQLiteConnection(
"Data Source=C:\yourFolder\yourDB.db3;Version=3;Password=password;")
conn.Open()
conn.ChangePassword(String.Empty)
conn.Close()
PS. The open source database manager SQLiteStudio is able to open files which were password-protected that way, as long as you choose System.Data.SQLite instead of Sqlite 3 as your database type. (Requires v 3.1.1, the current version).
I have inherited software to maintain. The previous version used a third party Datagridview substitute that isn't compatible with versions of Windows from Vista on. In attempting to put Datagridviews in I have run into a problem with connecting to the database.
I am trying to make a small program to play around with connection and SELECT outside of the original software so I can further understand what I am doing and without going through the full process of using the original software to get to the testing point.
Private Shared Function GetData(ByVal sqlCommand As String) As DataTable
Dim table As New DataTable()
Dim connectionString As String = "Data Source=.\SQLExpress;Integrated Security=true;" _
& "AttachDbFilename=C:blah\blah\blah.mdf;User Instance=true;"
Using con = New SqlConnection(connectionString)
Using command = New SqlCommand(sqlCommand, con)
Using da = New SqlDataAdapter(command)
da.Fill(table)
End Using
End Using
End Using
Return table
End Function
My SQL command is a simple "Select * FROM Setup" and the rest of the program is form loads, imports, and DataGridView formatting. I don't think it affects the SQL part and would be cumbersome to include here.
This results in what appears to be a closed connection.
![Connection Property] http://i.imgur.com/b5V3Qy5.png
This is a screenshot of my SQLExpress which might help diagnose connection problems.
![SQL Properties] http://i.imgur.com/bakBq5D.png
I've blurred out the computer name in grey, but I did notice that there was another computer name in pink. I don't know what it means other than maybe this database was originally created on another computer and has been copied and pasted.
Finally this is the connection string that the original software used:
"Data Source=.\SQLExpress;AttachDbFilename=C:\blah\blah\blah.mdf;Trust_Connection=Yes;"
I have also tried:
"Data Source=.\SQLExpress;AttachDbFilename=C:\blah\blah\blah.mdf;Trusted_Connection=Yes;User Instance=true"
Finally, this is my exception:
"An attempt to attach an auto-named database for file C:\blah\blah\blah.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share."
I got my alternate connection strings from www.connectionstrings.com.
You are missing the Open() command.
con.Open()
Full code listing. (Also a good idea is to wrap your code in a Try.... End Try block).
Private Shared Function GetData(ByVal sqlCommand As String) As DataTable
Dim table As New DataTable()
Dim connectionString As String = "Data Source=.\SQLExpress;Integrated Security=true;" _
& "AttachDbFilename=C:blah\blah\blah.mdf;User Instance=true;"
Using con = New SqlConnection(connectionString)
conn.Open()
Using command = New SqlCommand(sqlCommand, con)
Using da = New SqlDataAdapter(command)
da.Fill(table)
End Using
End Using
End Using
Return table
End Function
I'm trying to connect to to a foxpro table (.dbf) from a test vb.net form.
I recieve an OleDbException with the message "Cannot open file c:\emp\emptbl.dbf"
Have tried with both of the following connection strings:
Provider=VFPOLEDB.1;Data Source=C:\emp\emptbl.dbf
from the MSDN article here
Provider=vfpoledb;Data Source=C:\emp\emptbl.dbf;Collating Sequence=machine;
from connectionstrings.com
The latter seems to be the type to use when connecting to a single table, but the same exception is thrown regadless of which is used.
I can open and perform the same query okay in visual foxpro 6.0.
Here's my code:
Dim tbl As DataTable = New DataTable()
Using con = New OleDbConnection(conString)
cmd = New OleDbCommand() With {.Connection = con, .CommandType = CommandType.Text}
Dim sSQL As String = "SELECT * FROM(EMPTBL)"
cmd.CommandText = sSQL
Dim adp As OleDbDataAdapter = New OleDbDataAdapter(cmd)
Dim ds As DataSet = New DataSet()
con.Open()
adp.Fill(ds)
con.Close()
If (ds.Tables.Count > 0) Then
tbl = ds.Tables(0)
End If
End Using
Return tbl
The OleDB provider should only connect to the PATH where the tables are... not the actual file name. Once you connect to the PATH, you can query from ANY .Dbf file that is located in it
Provider=VFPOLEDB.1;Data Source=C:\emp
select * from emptbl where ...
You can also look at other connection string settings at
ConnectionStrings.com
UPDATE per comment.
It appears you are getting closer. with your attempt without the () parens. In VFP, within parens, it interprets that as "look for a variable called EMPTBL", and from its value is the name of the table to query from. Not something you would need to apply via OleDB connection.
Now, cant open the file is another. Is it POSSIBLE that another application has the table open and the file is in exclusive use? and thus can not be opened by the .net app too? Even for grins, if you open VFP, and just do a simple create table in the C:\Emp folder and put a single record in it, then you know no other program will be using it as it is a new file. Quit out of VFP and try to query THAT table. There should be no locks, no other program is expecting it, so it should never be opened by anything else and you should be good to go.
Hey all i am VERY new to a Oracle DB and i am trying to connect to it via VB.net 2010. I have been trying the following:
Dim myConnection As OleDbConnection
Dim myCommand As OleDbCommand
Dim dr As OleDbDataReader
myConnection = New OleDbConnection("Provider=MSDAORA.1;UserID=xxxx;password=xxxx; database=xxxx")
'MSDORA is the provider when working with Oracle
Try
myConnection.Open()
'opening the connection
myCommand = New OleDbCommand("Select * from emp", myConnection)
'executing the command and assigning it to connection
dr = myCommand.ExecuteReader()
While dr.Read()
'reading from the datareader
MessageBox.Show("EmpNo" & dr(0))
MessageBox.Show("EName" & dr(1))
MessageBox.Show("Job" & dr(2))
MessageBox.Show("Mgr" & dr(3))
MessageBox.Show("HireDate" & dr(4))
'displaying data from the table
End While
dr.Close()
myConnection.Close()
Catch ee As Exception
End Try
And i get the error on the Catch ee As Exception line: ORA-12560: TNS:protocol adapter error
I also have a tnsnames.ora file on my computer but i am unsure if i need to use that when connecting (or really, how too in the first place)? Is it needed for the code above?
I am trying to use a DNS-Less connection to the DB. Not sure if that is what it is doing in this or not?
Any help would be great!!! :o)
David
There are many ways: the one I use almost every time that doesn't require an entry in TNSNAMES.ORA is this:
Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=MyHost)(PORT=MyPort)))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=MyOracleSID)));User Id=myUsername;Password=myPassword;
And if you don't need an OleDb connection I think you should use System.Data.OracleClient or any other free provider (like DevArt dotConnect for Oracle Express)
Source: http://www.connectionstrings.com/oracle
I always use www.connectionstrings.com/ when I need to create a new connection string to the DB and when connection string format is not on top of my head.
I've succesfully synchronized both source and local db using the local database cache item in VS 2008.
However, I need to access the SQL CE db directly from within another dll/process, and without using a dataset. The reason being that my business object code does not use datasets.
The final code wouldlook something like this:
Dim conn As New SqlServerCe.SqlCeConnection("Data Source=C:\Development\UserDirectory\UserDirectory.DBSyncher\ProfDir.sdf;Persist Security Info=False;")
Dim cmd As New SqlServerCe.SqlCeCommand("Select EmailAddress from Employees Where ID=23", conn)
Dim returnString As String = ""
If conn.State = ConnectionState.Closed Then
conn.Open()
End If
returnString = cmd.ExecuteScalar
conn.Close()
cmd = Nothing
I notice something very strange using a dataset the synchronized changes are shown but accessing the CE database file directly returns old data - no synched data whatsoever.
What am I missing? Any help would be greatly appreciated.
Figured it out!
Forgot that CE is in process, thus it copies the database file(.sdf) to the Debug folder. You have to to reference that database not the one in your project. DOH!