I have a winforms app that uses sqlite to store data. Instead of shipping a blank database, can I use scripts to create the tables the first time the user uses the app? Can you point to a C# example?
Update: I want to avoid shipping a blank database. So if a user install the app for 1 user only, only his profile gets a copy. All users profile gets the database if the install is for all users.
Yes, this is possible:
When the application first runs, check if the database file exists.
If it doesn’t, open it with the Sqlite option FailIfMissing=False. This will create a new file.
Then, use SQL commands like CREATE TABLE ... to create the schema structure.
For the second step, I use code that looks something like this:
public DbConnection CreateConnectionForSchemaCreation(string fileName)
{
var conn = new SQLiteConnection();
conn.ConnectionString = new DbConnectionStringBuilder()
{
{"Data Source", fileName},
{"Version", "3"},
{"FailIfMissing", "False"},
}.ConnectionString;
conn.Open();
return conn;
}
Related
I am new to c#/.NET and developing an application with SQlite datbase and entity framework and it is all working fine during testing. I am specifying the below for the filepath to the .db file.
var path = AppDomain.CurrentDomain.BaseDirectory;
On deployment I need the application to create the database fresh, that doesn't contain the test data I was using during development. So I cannot simply copy the current .db file. Can anyone help with code that checks existence of database, and if not it will create new?
You can use this method:
private static void CreateFreshDb(string dbFilePath)
{
// Create the DB file
SQLiteConnection.CreateFile(dbFilePath);
// Create a table
var connectionString = $"Data Source={dbFilePath};Version=3;";
using (var connection = new SQLiteConnection(connectionString))
{
connection.Open();
string creationScript = "Create Table Person (Id int, Name varchar(20))";
SQLiteCommand command = new SQLiteCommand(creationScript, connection);
command.ExecuteNonQuery();
command.Dispose();
}
}
And call it like that:
string dbFilePath = "C:\\Db\\Database.db";
if (!File.Exists(dbFilePath))
{
CreateFreshDb(dbFilePath);
}
Note that I use the System.Data.SQLite library here.
An appliation that creates databases should be in principle a script that creates databases. If you application has its own business line which requires a database, but it is not intended to create a database at first, better you create it manually outside the code and then simply let the code choose between which database to use between testing and production, via appSettings or similar solution.
When I update my data:
using (SQLiteConnection conn = new SQLiteConnection(DB_PATH))
{
var query = conn.Table<kursy>().Where(k => k.kurs == kursStaryRubel).SingleOrDefault();
query.data = kursAktualnyData;
query.kurs = kursAktualnyRubel;
conn.Update(query);
}
Everything works fine. The data is updated. But when I close and open my application again, this data has old value - it's not updated. I'm using the same database, it is not recreated. Why is it happening?
My DB_PATH:
public static string DB_PATH = Path.Combine(ApplicationData.Current.LocalFolder.Path, "test.db");
My database file has property Copy to Output Directory set to Copy if Newer
I've solved the problem.
Unconsciously database was replaced at the start. The problem was that I created database in the Storage , not in the IsolatedStorage. I do not know if I understand this correct, but when it was created in Storage, the database was created in the memory of the application, and that's why database expires when I close app. But when I create database in IsolatedStorage it is permanently placed in the phone memory. And then even if I turn off the application, the database remained, because it was created in the phone memory, not in the application memory.
I'm looking to be able to dynamically create linked tables with C# in an accdb/mdb existing file. Is this possible? The idea would be for every linked table ALREADY in a given access database dynamically create a new linked table and then the second part of the problem would be to then rename name this newly created table to the pre existing table.
If its not already clear there is a migration going on from one database to another so every pre existing table has an equivalent table in the new database but they need to have the same name in the Access database in order for the queries to work etc.
Is this even possible?
EDIT:
I have created a test database that contains one linked table to an ODBC database. I have also created a simple query that just counts the rows. My C# code runs the query first and then attempts to change the connection string with the code:
var dbe = new DBEngine();
Database db = dbe.OpenDatabase(#"C:\Users\x339\Documents\Test.accdb");
foreach (TableDef tbd in db.TableDefs)
{
if (tbd.Connect.Length > 5)
{
if (tbd.Connect.Substring(0, 5).Equals("ODBC;"))
{
tbd.Connect = tbd.Connect.Replace("ODBC;DSN=ILACFEUC;UID=cloaseuc;DBQ=ILACFEUC;DBQ=W;APA=T;EXC=F;FEN=T;QTO=F;FRC=10;FDL=10;LOB=T;RST=T;BTD=F;BNF=F;BAM=IfAllSuccessful;NUM=NLS;DPM=F;MTS=F;MDI=F;CSR=F;FWC=F;FBS=64000;TLO=0;MLD=0;ODA=F;;TABLE=CLOASEUCDBA.T_BASIC_POLICY", "ODBC;DSN=ILACFEUC;UID=cloaseuc;DBQ=ILACFEUC;DBQ=W;APA=T;EXC=F;FEN=T;QTO=F;FRC=10;FDL=10;LOB=T;RST=T;BTD=F;BNF=F;BAM=IfAllSuccessful;NUM=NLS;DPM=F;MTS=F;MDI=F;CSR=F;FWC=F;FBS=64000;TLO=0;MLD=0;ODA=F;;TABLE=CLOASEUCDBA.T_BILLING_INFORMATION");
tbd.RefreshLink();
}
}
}
however it is not working. If I open the database up in access the connection string is unchanged?
It sounds like you really just want to change the external database to which the existing linked tables are connected. In that case you could do it in C# like this:
// This code requires the following COM reference in your project:
//
// Microsoft Office 14.0 Access Database Engine Object Library
//
// and the declaration
//
// using Microsoft.Office.Interop.Access.Dao;
//
// at the top of the class file
var dbe = new DBEngine();
Database db = dbe.OpenDatabase(#"C:\Users\Public\FrontEnd.accdb");
foreach (TableDef tbd in db.TableDefs)
{
if (tbd.Connect.Length > 10)
{
if (tbd.Connect.Substring(0, 10).Equals(";DATABASE="))
{
tbd.Connect = tbd.Connect.Replace("oldBackEnd.accdb", "newBackEnd.accdb");
tbd.RefreshLink();
}
}
}
db.Close();
As a quick background, I'm a beginner at database programming so forgive me if anything that I post here doesn't make sense or is outright dumb.
I'm trying to make a WinForm application that will allow users to connect to a .mdb Access 97 database of their choosing, allow the user to make changes (e.g. add new data rows on WinForm which will then be applied to the original .mdb database), and sync those changes across different .mdb Access 97 databases if desired.
To give you an idea of what I have so far. I have successfully connected to a .mdb Access 97 database using C# and I output the database table contents into a DataSet object from which I then dumped into a C1FlexGrid (code will follow momentarily). Now before anyone mentions anything, I cannot upgrade the database file to a newer version, so it has to stay as an Access 97 version file.
Here is the code I used to connect:
dbConnection = new OleDbConnection(#"Provider=Microsoft.JET.OLEDB.4.0;Data Source=" + path);
dbCommand = new OleDbCommand("SELECT * from MAIN", dbConnection);
dbDataAdapter = new OleDbDataAdapter(dbCommand);
dbDataSet = new DataSet("MasterLanguageDB");
dbConnection.Open();
dbConnectionIsOpen = true;
// connection is successful, unlock connected mode features
EnterDatabaseConnectedMode();
dbDataAdapter.Fill(dbDataSet);
flexGrid.DataSource = dbDataSet.Tables[0];
My question is this: is the C1FlexGrid that I now have populated with the .mdb database file contents "binded" to the .mdb file? Because 1, I didn't bind the datasource the way Microsoft suggests doing it by way of the Add Data Source wizard in Visual Studio 2008 (because the user can connect to any .mdb database they choose -- not just one) and 2, I want whatever changes I make to the C1FlexGrid to apply to the original database.
If the answer is no, how do I create that "binding" or add the rows to the database?
The ADO.NET classes like Dataset or DataTable are disconnected objects.
Meaning that they can't directly update the database.
The OleDbDataAdapter has a method called Update that takes care to send all the modified data to the database.
So, supposing you have a button somewhere to save your changes, then you need to call in the click event
dbDataAdapter.Update(dbDataSet);
However this requires that you keep the object instances at the class global level
Another point is the need to prepare the dbDataAdapter.InsertCommand, dbDataAdapter.UpdateCommand and dbDataAdapter.DeleteCommand.
These commands could be created simply using an instance of OleDbCommandBuilder just after you have set the SelectCommand
dbDataAdapter = new OleDbDataAdapter(dbCommand);
OleDbCommandBuilder cb = new OleDbCommandBuilder(dbDataAdapter);
I have an application that needs to store loads of data in a table format. I want something easy to configure, which is also in built with C#.NET. I don't want to have to include additional DLL files.
Also some links to tutorials, explaining the connection process and querying would be great. I'm assuming this is just like PHP, but which database type do I need?
It needs to be able to hold a lot of data and the ability to perform backups would be nice.
I'm not sure what you mean by "built in with C#.NET", but SQL Server Express comes with Visual Studio.
If you're looking for "a self-contained, embeddable, zero-configuration SQL database engine", you could try System.Data.SQLite.
If you want an offline database you could use SQL Server CE, as its a in-process database that does not require being attached to a server instance, which is really what you want then. Here is an example in C# on how you would connect, and populate a data table to manipulate some data.
// this connectionstring can also be an absolute file path
string connectionString = "Data Source=|DataDirectory|\mydatabase.sdf";
using (SqlCeConnection connection = new SqlCeConnection(connectionString)) {
try {
connection.Open();
}
catch (SqlCeException) {
// connection failed
}
using (SqlCeDataAdapter adapter = new SqlCeDataAdapter("SELECT * FROM <table>", connection)) {
using (DataTable table = new DataTable("<table>")) {
adapter.Fill(); // Populate the table with your select statement
// do stuff with the datatable
// example:
foreach (DataRow row in table.Rows) {
row["mycolumn"] = "somedata";
}
table.AcceptChanges();
}
}
}
You can even use commands instead of data tables
using (SqlCeCommand command = new SqlCeCommand("DELETE FROM <table> WHERE id = '0'", connection)) {
command.ExecuteNonQuery(); // executes command
}
Have a look at the ease of SQL Server Compact
Not build-in but easily added, no install and free.