In my C# app I can switch between Online SQL-Server connection and local SQLCE (sdf file) connection. Both DBs are the same in structure and indexes.
But using the local SDF file through SqlCeConnection is so much slower - 20 times slower when doing a lot of calls.
Example:
using (DbConnection connection = new SqlCeConnection(ConnectionString))
{
connection.Open();
using (DbCommand cmd = GetSqlCommand("select * from t", connection))
{
try
{
var reader = cmd.ExecuteReader();
while (reader.Read())
{
...
}
reader.Close();
}
catch (Exception e) { }
}
}
What is going on here - can I optimize that?
Keep a single connection open and unused for the lifetime of your app, SQL Compact does not have connection pooling.
In addition, opening a SqlCeConnection can be slow because of:
The database file has been created on another platform
The ACL (Access Control List) on the RSA folder is corrupt
Invalid Internet Proxy configuration
More info here: http://erikej.blogspot.dk/2013/08/faq-why-is-opening-my-sql-server.html
Related
I created a sqlite database in unity... and tried to connect with this function.
void AddScores(string conn)
{
IDbConnection dbconn;
dbconn = (IDbConnection)new SqliteConnection(conn);
dbconn.Open();
using(IDbCommand dbCmd = dbconn.CreateCommand())
{
// string sqlQuery = "SELECT Id FROM PickAndPlace ";
string sqlQuery= "INSERT INTO PickAndPlace (Id) VALUES (324)";
dbCmd.CommandText = sqlQuery;
using(IDataReader reader = dbCmd.ExecuteReader())
{
while (reader.Read())
{
print(reader.GetInt32(0));
}
dbconn.Close();
reader.Close();
dbCmd.Dispose();
}
}
}
The following code not working if I try insert values...and it is showing this error "The database file is locked:
database is locked" But If I try select this works fine.So where is my mistake?
Sqlite generally accepts a single "connection". Once one application connects to the database, which means just acquiring a write lock on it, no other applications can access it for writes, but can access it for reads. Which is just the behaviour you are seeing. See File Locking And Concurrency Control in SQLite Version 3 for a bunch more details about how this works, the various locking states etc.
But in principle, you can only have a single connection open. So somehow you have more than one. Either you forget to close some connections, or multiple threads or applications are trying to modify it. Or perhaps some error occurred and left the locking files in a bad state.
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.
Connection string that my app is using to connect to DB is the following:
private const string oradb = "Data Source=(DESCRIPTION=(ADDRESS_LIST="
+ "(ADDRESS=(PROTOCOL=TCP)(HOST=host.name)(PORT=1521)))"
+ "(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=service.name)));"
+ "User Id=myusername;Password=mypass;";
In all DB access points of my app I am using the following pattern:
OracleConnection conn = new OracleConnection(oradb);
try
{
Console.WriteLine("Opening DB Connection...");
conn.Open();
string queryString = string.Format(#"SELECT ...");
using (OracleCommand command = new OracleCommand(queryString, conn))
{
using (OracleDataReader reader = command.ExecuteReader())
{
while (reader.Read())
{
...
}
}
}
}
catch (Exception e)
{
Console.WriteLine("Exception occured during DB access: {0}", e.Message);
dbr.Error = e.Message;
}
finally
{
Console.WriteLine("Closing DB connection");
conn.Close();
conn.Dispose();
}
For sure I am properly handling exceptions and in try/catch/finally closing AND disposing connection object. However, often I am receiving oracle service message that I am holding oracle sessions. Moreover, if I just leave my app open and next day try to make operation, I am getting ora-12537 network session end of file exception first time, then second attempt is going through. After some reading it looks like I have to disable connection pool. If this is the right way to solve, how to disable pool? If not, then what other thing can be wrong?
You could add Pooling=False in the connection string, but this means a new connection is created each time.
+ "User Id=myusername;Password=mypass;Pooling=False;";
Take a look at this article, it might help with your issue. Also, take a look at this website page, specifically the Using Connection Pooling section
Version 6.4.4:
Using the most basic implementation of MySqlConnection, the following code takes 2-5 seconds per connection when preloading the connection pool to reach the "Min Pool Size" configured in my connection string.
Any ideas why it is taking so long, how to fix, or workarounds?
Connection String:
<add name="users" connectionString="server=192.168.1.2;User Id=dbuser;password=dbpassword;database=users;Pooling=true;Min Pool Size=10;Max Pool Size=50;Persist Security Info=True;" />
Code
private static void MySqlConnectionTester()
{
string connectionString = ConfigurationManager.ConnectionStrings["users"].ConnectionString;
using (var connection = new MySqlConnection(connectionString))
{
using (var command = connection.CreateCommand())
{
command.CommandText = "select * from users;";
try
{
connection.Open(); // This line hangs until "Min Pool Size" is reached.
using (var reader = command.ExecuteReader())
{
while(reader.Read())
{
// Read results
}
}
}
catch(Exception ex)
{
// Log exception
}
finally
{
connection.Close();
}
}
}
}
At MySQL's homepage they write that you should avoid creating, opening and closing the connection object youself, instead you should use the helper class which should work better with connectionpooling.
I have not tested it, but was something I just read :)
The issue was also present on our side with MySql Connector .Net 6.6.5. The MySql Connector .Net 6.8.3 is solving this issue.
Fabrice
I've tried literally 50+ different attempts at my connection string for my local database and nothing seems to work. I'm essentially just trying to open a connection the database file so I can dump in the data I've pulled out of my excel spreadsheet. I'm using Visual C# making an offline winform application.
No matter what connection string I try in my app.config, it always fails when it tries to write "dReader" to the database.
The error is usually this depending on what string I try:
"A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)"
I've gone through many online examples and resources and none seem to work. I'm hoping someone here can point out why it's failing.
Here is my app.config in its latest form:
<connectionStrings>
<add name="DDP_Project.Properties.Settings.DDP_DatabaseConnectionString"
connectionString="Data Source=E:\Other DDP Projects\DDP_Project_SDF\DDP_Project\DDP_Database.sdf;"
providerName="Microsoft.SqlServerCe.Client.3.5" />
</connectionStrings>
Here is my form code:
private void Profiles_Click(object sender, EventArgs e)
{
profilesDialog.FileName = "[YOUR_UPLOAD_FILE_HERE]";
var result = profilesDialog.ShowDialog();
if (result == DialogResult.OK)
{
HandleFileSelection();
}
}
private void HandleFileSelection()
{
var file = profilesDialog.FileName;
// Create a connection to the file datafile.sdf in the program folder
string dbfile = new System.IO.FileInfo(System.Reflection.Assembly.GetExecutingAssembly().Location).DirectoryName + "\\DDP_Database.sdf";
SqlCeConnection connection = new SqlCeConnection("datasource=" + dbfile);
string strConnection = ConfigurationManager.ConnectionStrings["DDP_Project.Properties.Settings.DDP_DatabaseConnectionString"].ConnectionString;
//Create connection string to Excel work book
string excelConnectionString = string.Format(
#"Provider=Microsoft.Jet.OLEDB.4.0;
Data Source=""{0}"";
Extended Properties=""Excel 8.0;HDR=YES;""", file
);
//Create Connection to Excel work book
OleDbConnection excelConnection = new OleDbConnection(excelConnectionString);
OleDbCommand cmd = new OleDbCommand("SELECT [ID],[STATUS],[FAN_NUM],[PROFILE_NAME],[DESTINATION_HOST],[USER_ID],[USER_PASSWORD],[PROTOCOL],[PORT],[PATH],[CONTACT_NAME],[CONTACT_EMAIL],[CONTACT_PHONE],[CONTACT_ALT_PHONE],[CONTACT_CITY],[CONTACT_STATE],[CONTACT_CONTACT_TIME] FROM [Sheet1$]", excelConnection);
excelConnection.Open();
OleDbDataReader dReader;
dReader = cmd.ExecuteReader();
SqlBulkCopy sqlBulk = new SqlBulkCopy(strConnection);
sqlBulk.DestinationTableName = "Profiles";
sqlBulk.ColumnMappings.Add("ID", "ID");
sqlBulk.ColumnMappings.Add("STATUS", "STATUS");
sqlBulk.ColumnMappings.Add("FAN_NUM", "FAN_NUM");
sqlBulk.ColumnMappings.Add("PROFILE_NAME", "PROFILE_NAME");
sqlBulk.ColumnMappings.Add("DESTINATION_HOST", "DESTINATION_HOST");
sqlBulk.ColumnMappings.Add("USER_ID", "USER_ID");
sqlBulk.ColumnMappings.Add("USER_PASSWORD", "USER_PASSWORD");
sqlBulk.ColumnMappings.Add("PROTOCOL", "PROTOCOL");
sqlBulk.ColumnMappings.Add("PORT", "PORT");
sqlBulk.ColumnMappings.Add("PATH", "PATH");
sqlBulk.ColumnMappings.Add("CONTACT_NAME", "CONTACT_NAME");
sqlBulk.ColumnMappings.Add("CONTACT_EMAIL", "CONTACT_EMAIL");
sqlBulk.ColumnMappings.Add("CONTACT_PHONE", "CONTACT_PHONE");
sqlBulk.ColumnMappings.Add("CONTACT_ALT_PHONE", "CONTACT_ALT_PHONE");
sqlBulk.ColumnMappings.Add("CONTACT_CITY", "CONTACT_CITY");
sqlBulk.ColumnMappings.Add("CONTACT_STATE", "CONTACT_STATE");
sqlBulk.ColumnMappings.Add("CONTACT_CONTACT_TIME", "CONTACT_CONTACT_TIME");
sqlBulk.WriteToServer(dReader);
sqlBulk.Close();
excelConnection.Close();
}
private void profilesDialog_FileOk(object sender, EventArgs e)
{
}
}
}
Try this...
First:
Create first a test method which you may check if you can connect to sqlcedatabase.
private void testconnection()
{
string strConnection = ConfigurationManager.ConnectionStrings["DDP_Project.Properties.Settings.DDP_DatabaseConnectionString"].ConnectionString;
using (var conn = new SqlCeConnection(string.Format("Data Source={0};Max Database Size=4091;Max Buffer Size = 1024;Default Lock Escalation =100;", strConnection)))
{
conn.Open();
try
{
//your Stuff
}
catch (SqlCeException)
{
throw;
}
finally
{
if (conn.State == ConnectionState.Open) conn.Close();
}
}
}
Second:
Just Load your excel file Data into a Datatable and use foreach then save it on your sql ce database file..
//Something like
//oledbcon
//oledb dataadapter
//datatable
// dapt.Fill(dt);
foreach(DataRow excel in dt.Rows)
{
ceCmd.Parameters.AddWithValue("ID",excel["ID"]);
ceCmd.ExecuteNonQuery();
}
Regards
I think the problem you are seeing is that you are trying to use a SqlConnection to connect to a SQL Compact database. The .sdf is a compact database and you have to use the SqlCeConnection to connect to it. You create the connection using this but then you don't use it. Instead you pass in the connection string to the SqlBulkCopy object which implicitly creates a SqlConnection from that string. I'm assuming it is on that line where you are getting the error. If you notice the namespace of the SqlBulkCopy is System.Data.SqlClient. The reason you are seeing the error is that its trying to go through SQL Server to make the connection and cannot resolve your connection string to a SQL Server database. Unfortunately, I don't think the System.Data.SqlServerCe has the equivalent to the SqlBulkCopy. Stick to using classes in System.Data.SqlServerCe and things should work as expected. You just will have to do the processing in a more manual fashion.
According to this post, SqlBulkCopy isn't supported with SqlCe.