I have an application built on Microsoft's Sync Framework. Data is entered and stored in database configured with the sync framework wizard. From what I understand, this puts a clone of the server database in a local directory and the database version is SQL Compact edition.
The user will on occasion use the application offline and will need information from one database in order to fill another. They will select a tool from the Tools database and a device with certain parameters from the device database. In order to do this I need to be able to query the local database when offline.
First I attempted to fill my comboboxes by using the local ConnectionString from my settings.
Dim conn As New SqlConnection(My.Settings.ClientDatabaseConnectionString)
conn.Open()
Dim dat As SqlDataAdapter = New SqlDataAdapter("SELECT Distinct InstrumentType FROM CreateScriptTable", conn)
Dim dt As New DataSet
dat.Fill(dt, "TestScriptTable")
cbInst.DataSource = dt.Tables("TestScriptTable").DefaultView
cbInst.DisplayMember = "InstrumentType"
cbInst.ValueMember = "InstrumentType"
Next as it is an SQL ce datbase I used the SQLCeConnection:
Dim conn As SqlCeConnection
conn = New SqlCeConnection("Data Source=|DataDirectory|\TestsDatabase4.sdf;Max Database Size=2047")
Dim dat As SqlCeDataAdapter = New SqlCeDataAdapter("SELECT Distinct InstrumentType FROM TestScriptTable", conn)
Dim dt As New DataSet
dat.Fill(dt, "TestScriptTable")
cbInst.DataSource = dt.Tables("TestScriptTable").DefaultView
cbInst.DisplayMember = "InstrumentType"
cbInst.ValueMember = "InstrumentType"
Various formats for the local connection string were passed into SQLConnection() including removing Max Database Size=2047
Neither of these approaches worked so I tried to change the connection string at runtime following the tutorial here
This did not work either so at the moment I am unable to retrieve any data at will offline.
Has anyone any thoughts on this? Thanks.
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've added an access db to my project as a datasource. So I get the automatically generated tableadapters class and therefore, access to the table adapter instance which includes the connection string. I'm using this to open a connection to my db so I can first, delete some records, and then replace them with new records.
The queries seem to work because the .executenonquery does return the rows affected. I even tried a delete * command to be sure. But, when I open the database everything is the same.
I had some ideas as to why. I thought the connection string returned by the tableadapter might be goofy because it contains a generic pointer to the project's data directory.
Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\DupeMDB.mdb;Persist Security Info=True
I also thought maybe I had a problem with the Build Action or the Copy to Output Directory. I really don't understand the mechanics behind these two things. I think maybe the copy to output directory thing might be the culprit.
Here's me goal. I want to deploy this project to my secretary so she can use the program to deal with a duplicate record list etc. The data has to go with the program. I want to package this .mdf file with the deployment and get it back from her when she's done with it. I am so close to the end here (writing back to the table). Does anyone know why the table won't update?
Dim Connector As DupeTblTableAdapter = New DupeTblTableAdapter
Dim Conn As New System.Data.OleDb.OleDbConnection
Conn = Connector.Connection
Conn.ConnectionString = Connector.Connection.ConnectionString
MsgBox(Conn.ConnectionString)
Dim Comm As System.Data.OleDb.OleDbCommand
Conn.Open()
For Each DR In DeleteRecords
Comm = New System.Data.OleDb.OleDbCommand($"DELETE from DupeTbl where DupeTbl.CUST_NO={DR.ToString}", Conn) '
Dim aff As Integer = Comm.ExecuteNonQuery
'MsgBox(aff)
Comm = Nothing
Next
For Each RR In ReplaceRecords
Comm = New System.Data.OleDb.OleDbCommand($"INSERT INTO DupeTbl ( CUST_NO, PREDIR, POSTDIR, SUFFIX, CUSTSIZE, AddFlag, IgnoreRecord ) VALUES ({RR.Cust_No}, '{RR.PreDir}', '{RR.PostDir}', '{RR.Suffix}', {RR.Size}, {RR.AddFlag}, {RR.Ignore});", Conn)
Comm.ExecuteNonQuery()
Comm = Nothing
Next
Conn.Close()
The issue in such cases is usually the working database being overwritten on each build. When adding a local data file to your project, it is added as a source file in the project folder. By default, the Copy to Output Directory property is set to Copy Always. That means that every time you build your project, which will happen each time you make a code change and run the project by default, the source file will be copied over the top of the working database in the output folder, thus wiping out any changes you made while debugging. To prevent this, change that property to Copy if Newer, which means that the working database will only be overwritten if you make a change to the source database, e.g. modify the schema.
Dim Connector As DupeTblTableAdapter = New DupeTblTableAdapter
Dim Conn As New System.Data.OleDb.OleDbConnection
Conn = Connector.Connection
Conn.ConnectionString = Connector.Connection.ConnectionString
MsgBox(Conn.ConnectionString)
Dim Comm As System.Data.OleDb.OleDbCommand
Conn.Open()
For Each UR In UpdateRecords
Comm = New System.Data.OleDb.OleDbCommand($"UPDATE DupeTbl SET CUST_NO = <NewValue>, PREDIR = <NewValue, POSTDIR = <NewValue> etc. where DupeTbl.CUST_NO={DR.ToString}", Conn) '
Dim aff As Integer = Comm.ExecuteNonQuery
'MsgBox(aff)
Comm = Nothing
Next
Conn.Close()
Rewriting a legacy system in VB 2013 Express which connects to an Access DB. I've set up the Data Connection and have a DataSet with all the tables. The code needs to do the following:
Delete all the rows in the "extract" table;
Read in and parse the new data;
Write the new data to the "extract" table.
I've got the reading and parsing part done, but I need help with the deleting and writing part. Nothing I try seems to work.
This is what i've tried:
Dim sqlConnection1 As New System.Data.SqlClient.SqlConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\CLI_CRVM.accdb")
Dim cmd As New System.Data.SqlClient.SqlCommand()
cmd.CommandType = System.Data.CommandType.Text
cmd.CommandText = "DELETE FROM extract"
cmd.Connection = sqlConnection1
You are trying to use System.Data.SqlClient, but that is specifically for working with Microsoft SQL Server databases. The example code in your question will fail with
Keyword not supported: 'provider'.
For an OLEDB connection to your Access database, use System.Data.OleDb.
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.
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!