I am trying to run a .NET project someone gave me that contains a database MDF file and uses LINQ queries in the C# code, such as:
db = new DataClasses1DataContext();
using (db)
{
res01 r = new res01();
r.comb_bars = 1;
r.end_dte = b_list.Last().dteTme.Date;
r.pers = pers;
r.st_dte = b_list.First().dteTme.Date;
r.sym = sym;
db.res01s.InsertOnSubmit(r);
db.SubmitChanges();
}
I see that this code runs when I debug it, but it doesn't seem like any rows were added to the database. Yet, I didn't get any errors while running the code. I am using Visual C# Express 2010. How can I see what has been added in the database MDF file that is part of the project?
Data is stored in the database file inside bin/Debug folder. Open that and check.
See this for more details on connecting to compact db
try to rebind() the grid. because the data have to be reloaded.
Related
I've got a problem resolving my SQLite Database issue.
As the title says, I'm "simply" trying to add some data into a particular table of the database file using SQLite - with the Microsoft.Data.SQLite package.
The code is executed without any errors and even the SQL-Statement execution returns that one row altered. But when I take a look into the db with the db-browser the "inserted" row, simply isn't there at all. This is the code executed:
SqliteConnectionStringBuilder _sqlconsb = new SqliteConnectionStringBuilder();
_sqlconsb.DataSource = _SqliteDatabase;
_sqlconsb.Mode = SqliteOpenMode.ReadWrite;
SqliteConnection _sqlconn = new SqliteConnection(_sqlconsb.ConnectionString);
_sqlconn.Open();
SqliteCommand _sqlcmd = _sqlconn.CreateCommand();
_sqlcmd.CommandText = #"INSERT INTO Mediatypes (Name, Type) VALUES ('Hurrey-1', 'i')";
int _numInsert = _sqlcmd.ExecuteNonQuery();
_sqlconn.Close();
return _numInsert;
I created a complete new WPF-Application with some buttons and executed the same piece of code in that new app. There it also executes without any issues and the data is indeed added to the db file, which I again checked with the db browser.
I've got no idea, with this particular code adds the new row of data in the test app, but does'nt do it's job in my app. I'm also complete lost in further debbuging this issue, because it's executed without any issues.
One more point to consider, I've other methods in my app which are able to add data successfully to the database into other tables. So i think it sholdn't be the database file itself nor the MS.Data.SQLite package in my solution.
I hope there's anyone out there who's able to point me into the right direction to get this debbuged and or solved ...!
My Code :
var dbpath = Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "ot.db3");
Context myContext = null;
try
{
var dbcon = new SQLiteConnection(dbpath);
var db= dbcon.Query<records>("SELECT * FROM records WHERE sno = ? ", "1");
int count = db.Count;
}
catch (IOException ex)
{
var reason = string.Format("The database failed to create - reason {0}", ex.Message);
Toast.MakeText(myContext, reason, ToastLength.Long).Show();
}
I Create a Sqlite Database from my SQL Server Database.
Now I save it to my Phone on this path (Android/Data/Application/File)
Now using Sqlite-net-pcl nugget package for Sqlite Connection the connection works fine showing have no error.
When I try to read a table from database this Give any error that "No Such Table exist in database". And the table exists in the database and is populated with data.
What can I do?
Thanks in advance
Why are you writing the SQL query? You could make it more simple, something like, conn.Get(id);
You will only need to add [PrimaryKey] to your PK in the model.
Also, I suggest you to not use SQLite.SQLiteConnection and use SQLiteAsyncConnection instead, so you will be able to get data using "await conn.GetAsync(id)" and this way it won't block the main thread.
Create a Blank Database – A database reference can be created by passing the file path the SQLiteConnection class constructor. You do not need to check if the file already exists – it will automatically be created if required, otherwise the existing database file will be opened.
var db = new SQLiteConnection (dbPath);
Save Data – Once you have created a SQLiteConnection object, database commands are executed by calling its methods, such as CreateTable and Insert like this:
db.CreateTable<Stock> ();
db.Insert (newStock); // after creating the newStock object
Retrieve Data – To retrieve an object (or a list of objects) use the following syntax:
var stock = db.Get<Stock>(5); // primary key id of 5
var stockList = db.Table<Stock>();
For more info use following link:
https://developer.xamarin.com/guides/android/application_fundamentals/data/part_3_using_sqlite_orm/#Using_SQLite.NET
You need to check in your DB file if the table really exists.
Extract the database from your Android device/simulator with ADB
Example: adb pull //.db .
It will download the DB file to your computer.
Then, use a tool such as "DB Browser for SQLite" (http://sqlitebrowser.org/) to open your DB file and check if your table exists.
Other common mistakes when using SQLite with Android are:
the file is not found (the path in your connectionstring is not good)
the name is not the one your think (maybe in your case, it is "Record" and not "Records")
Hope it will help.
I have following C# code in a console application.
Whenever I debug the application and run the query1 (which inserts a new value into the database) and then run query2 (which displays all the entries in the database), I can see the new entry I inserted clearly. However, when I close the application and check the table in the database (in Visual Studio), it is gone. I have no idea why it is not saving.
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data.SqlServerCe;
using System.Data;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
try
{
string fileName = "FlowerShop.sdf";
string fileLocation = "|DataDirectory|\\";
DatabaseAccess dbAccess = new DatabaseAccess();
dbAccess.Connect(fileName, fileLocation);
Console.WriteLine("Connected to the following database:\n"+fileLocation + fileName+"\n");
string query = "Insert into Products(Name, UnitPrice, UnitsInStock) values('NewItem', 500, 90)";
string res = dbAccess.ExecuteQuery(query);
Console.WriteLine(res);
string query2 = "Select * from Products";
string res2 = dbAccess.QueryData(query2);
Console.WriteLine(res2);
Console.ReadLine();
}
catch (Exception e)
{
Console.WriteLine(e);
Console.ReadLine();
}
}
}
class DatabaseAccess
{
private SqlCeConnection _connection;
public void Connect(string fileName, string fileLocation)
{
Connect(#"Data Source=" + fileLocation + fileName);
}
public void Connect(string connectionString)
{
_connection = new SqlCeConnection(connectionString);
}
public string QueryData(string query)
{
_connection.Open();
using (SqlCeDataAdapter da = new SqlCeDataAdapter(query, _connection))
using (DataSet ds = new DataSet("Data Set"))
{
da.Fill(ds);
_connection.Close();
return ds.Tables[0].ToReadableString(); // a extension method I created
}
}
public string ExecuteQuery(string query)
{
_connection.Open();
using (SqlCeCommand c = new SqlCeCommand(query, _connection))
{
int r = c.ExecuteNonQuery();
_connection.Close();
return r.ToString();
}
}
}
EDIT: Forgot to mention that I am using SQL Server Compact Edition 4 and VS2012 Express.
It is a quite common problem. You use the |DataDirectory| substitution string. This means that, while debugging your app in the Visual Studio environment, the database used by your application is located in the subfolder BIN\DEBUG folder (or x86 variant) of your project. And this works well as you don't have any kind of error connecting to the database and making update operations.
But then, you exit the debug session and you look at your database through the Visual Studio Server Explorer (or any other suitable tool). This window has a different connection string (probably pointing to the copy of your database in the project folder). You search your tables and you don't see the changes.
Then the problem get worse. You restart VS to go hunting for the bug in your app, but you have your database file listed between your project files and the property Copy to Output directory is set to Copy Always. At this point Visual Studio obliges and copies the original database file from the project folder to the output folder (BIN\DEBUG) and thus your previous changes are lost.
Now, your application inserts/updates again the target table, you again can't find any error in your code and restart the loop again until you decide to post or search on StackOverflow.
You could stop this problem by clicking on the database file listed in your Solution Explorer and changing the property Copy To Output Directory to Copy If Newer or Never Copy. Also you could update your connectionstring in the Server Explorer to look at the working copy of your database or create a second connection. The first one still points to the database in the project folder while the second one points to the database in the BIN\DEBUG folder. In this way you could keep the original database ready for deployment purposes and schema changes, while, with the second connection you could look at the effective results of your coding efforts.
EDIT Special warning for MS-Access database users. The simple act of looking at your table changes the modified date of your database ALSO if you don't write or change anything. So the flag Copy if Newer kicks in and the database file is copied to the output directory. With Access better use Copy Never.
Committing changes / saving changes across debug sessions is a familiar topic in SQL CE forums. It is something that trips up quite a few people. I'll post links to source articles below, but I wanted to paste the answer that seems to get the best results to the most people:
You have several options to change this behavior. If your sdf file is part of the content of your project, this will affect how data is persisted. Remember that when you debug, all output of your project (including the sdf) if in the bin/debug folder.
You can decide not to include the sdf file as part of your project and manage the file location runtime.
If you are using "copy if newer", and project changes you make to the database will overwrite any runtime/debug changes.
If you are using "Do not copy", you will have to specify the location in code (as two levels above where your program is running).
If you have "Copy always", any changes made during runtime will always be overwritten
Answer Source
Here is a link to some further discussion and how to documentation.
I'm adding new lines to a database for our company's "order list" for each order created, using the firebird ado.net client. The code i've written works fine for listing items, but inserting new ones doesn't appear elsewhere (e.g. in flamerobin). What I think is happening is that the transaction isn't being committed, seeing as it's recognised within my code (can't add duplicate values).
Code:
using (FbConnection fbCon = new FbConnection)
{
fbCon.Open();
***command w/ parameterised command string***
using (FbTransaction fbTrans = fbCon.BeginTransaction())
using FbCommand orderCommand = new FbCommand(cmdString, fbCon, fbTrans)
{
***Adding parameters and values***
try
{
int recordsAffected = orderCommand.ExecuteNonQuery();
fbTrans.Commit();
}
catch (FbException E)
{
fbTrans.Rollback();
fbCon.Close();
throw E
}
}
recordsAffected returns 1 but I am not able to see the updated values in flamerobin or the db management program. Am i missing something?
If anyone else runs into this problem, it's in Visual Studio's debugging settings. https://visualstudiomagazine.com/blogs/tool-tracker/2012/05/dealing-with-local-databases-or-why-your-updates-dont-stick.aspx explains pretty clearly, but basically VS makes a copy of your database in bin/Debug of your project (Ostensibly to not mess with your data) but if you actually need to use/view the data externally, either link your external application to the debug database (e.g. flamerobin). You may also need to set your project database settings to Copy if Newer if you want your updates to stay, as the default setting copies the database into the folder each time you run your c# app.
I am using VS2010 , and I am building a simple wpf application using C#
I have built a database using SQL Server 2008
in my application I created a LINQ to SQL class and created a dbml file
then I created a datacontect and did everything right
BUT
when I can't aaccess my database file everytime I try to , I mean when I insert anew row in my datacontexct I can check it and see it but when I look in my mdf file I can't find anything
I think that my datacontexct must be connected to my database file somehow
please help me because I seriously need it
The connection string, that is passed to the datacontext, references the MDF.
// Northwnd inherits from System.Data.Linq.DataContext.
Northwnd nw = new Northwnd(#"northwnd.mdf");
var cityNameQuery =
from cust in nw.Customers
where cust.City.Contains("London")
select cust;
foreach (var customer in cityNameQuery)
{
if (customer.City == "London")
{
customer.City = "London - Metro";
}
}
// you must call this this commit the changes
nw.SubmitChanges();
Call .SubmitChanges() on your DataContext after adding an item.