I'm currently programming a bot for Twitch, where we want to store settings in a database.
The database itself is pre-created, so all columns which are requested, are there.
Somehow, when using the reader object, it immediately throws an IndexOutOfRangeException. I don't know what causes this error.
public static void GetConfigFromDb()
{
try
{
SQLiteConnection conn = new SQLiteConnection("Data Source=OakSettings.sqlite;");
conn.Open();
string sql = "SELECT * FROM oak_settings";
SQLiteCommand command = new SQLiteCommand(sql, conn);
SQLiteDataReader reader = command.ExecuteReader();
while (reader.Read())
{
//StreamerOAuthKey = (string)reader["StreamerOAuthToken"];
//BotOAuthKey = (string)reader["BotOAuthToken"];
//StreamerUsername = (string)reader["StreamerTwitchUsername"];
//BotUsername = (string)reader["BotTwitchUsername"];
StreamerOAuthKey = reader.GetString(reader.GetOrdinal("StreamerOAuthToken"));
BotOAuthKey = reader.GetString(reader.GetOrdinal("BotOAuthToken"));
StreamerUsername = reader.GetString(reader.GetOrdinal("StreamerTwitchUsername"));
BotUsername = reader.GetString(reader.GetOrdinal("BotTwitchUsername"));
}
conn.Close();
}
catch (Exception ex)
{
System.Windows.MessageBox.Show(ex.ToString());
}
}
The only occasion when this method gets called, is on startup of the application. The part which is commented, was the way I did it before, but then I changed it, in hope this was causing the error.
What causes the error?
Related
First post here. I'm trying to create a website that fetches data from an Oracle database and returns some tables. I was able to connect my database fine and made a DataConnector that returns a list of CodeDesc objects. My main problem right now is simply displaying that data to the screen, preferably in the form of a drop down list but I'm using a GridView for now.
Here's my front end:
protected void Button1_Click(object sender, EventArgs e)
{
DataConnector dc = new DataConnector();
GridView2.DataSource = dc.getCodeTypes();
GridView2.DataBind();
}
When I click the button, nothing is generated and the debugger only says "Exception thrown: 'System.ArgumentException' in Oracle.DataAccess.dll" Any help would be appreciated. This is my first time doing web development and it's been a struggle to get even this far. I'm using Visual Studio 2015
Back End:
//Create datatable to get info from db & return results
public List<CodeDesc> getCodeTypes()
{
try
{
OracleConnection con = new OracleConnection(connString);
con.Open();
string query = "select id, descr from code_desc where code_type_id = 0";
// Create the OracleCommand
OracleCommand cmd = new OracleCommand();
cmd.Connection = con;
cmd.CommandType = CommandType.Text;
// Execute command, create OracleDataReader object
OracleDataReader reader = cmd.ExecuteReader();
List<CodeDesc> L = new List<CodeDesc>();
while (reader.Read())
{
CodeDesc c = new CodeDesc();
c.id = reader.GetInt32(0);
c.description = reader.GetString(1);
L.Add(c);
}
// Clean up
reader.Dispose();
cmd.Dispose();
con.Dispose();
System.Diagnostics.Debug.WriteLine(L);
return L;
}
catch (Exception ex)
{
// catch clause here...
}
}
CodeDesc:
public class CodeDesc
{
public int id { get; set; }
public string description { get; set; }
}
Any help would be great.
You never set the query string to the CommandText property of the OracleCommand. Of course this can only result in an exception when you try to execute your command.
Said that, remember that every disposable object should be enclosed in a using statement. This is very important in case of exceptions because the correct closing and disposing is executed automatically exiting from the using block
public List<CodeDesc> getCodeTypes()
{
try
{
List<CodeDesc> L = new List<CodeDesc>();
string query = "select id, descr from code_desc where code_type_id = 0";
using(OracleConnection con = new OracleConnection(connString))
using(OracleCommand cmd = new OracleCommand(query, con))
{
con.Open();
// Execute command, create OracleDataReader object
using(OracleDataReader reader = cmd.ExecuteReader())
{
while (reader.Read())
{
CodeDesc c = new CodeDesc();
c.id = reader.GetInt32(0);
c.description = reader.GetString(1);
L.Add(c);
}
}
}
System.Diagnostics.Debug.WriteLine(L);
return L;
}
I ran into a problem where passing a connection from a TableAdapter to some methods throws an exception stating the connectionstring isn't initialized. There are quite a few questions on SO with this exception but none were passing the connection and most were because the ConnectionString was null. Weird thing is I used MessageBox.Show(connection.ConnectionString); through out the chain of methods and I receive a valid connection string at every step. This is a somewhat complicated program that is in production but I will try to simplify the code for this question...
This is the postInventoryData method, which takes a DataGridView with inventory items and iterates through it posting them to the inventory. I use a TransactionScope to ensure the changes are safely rolled back in the event of an error. If an item is a kit(an item comprised of other items) I must iterate through those items and remove them from the inventory. The problem occurs when I check whether or not the item is a kit.
public bool postInventoryData(DataGridView dgv)
{
bool successful = true;
TestDataSetTableAdapters.inentoryTrxTableAdapter inventoryTrxAdapter =
new TestDataSetTableAdapters.inentoryTrxTableAdapter();
try
{
using (TransactionScope trxScope = new TransactionScope
(TransactionScopeOption.Required, new System.TimeSpan(0, 15, 0)))
{
MessageBox.Show(inventoryTrxAdapter.Connection.ConnectionString); // <-- Valid ConnectionString
inventoryTrxAdapter.OpenConnection();
for (int i = 0; i < dgv.Rows.Count; i++)
{
//parameter values
string departmentCode = dgv.Rows[i].Cells["Department_Code"].Value.ToString();
string machineCode = dgv.Rows[i].Cells["Machine_Code"].Value.ToString();
string operatorCode = dgv.Rows[i].Cells["Operator_Code"].Value.ToString();
string itemNumber = dgv.Rows[i].Cells["Item_Number"].Value.ToString();
double? qtyProduced = Convert.ToDouble(dgv.Rows[i].Cells["Quantity"].Value.ToString());
bool isKit =
businessLayer.isItemNumberKit
(inventoryTrxAdapter.Connection, itemNumber); // <-- CULPRIT!
// Inserts the item
dailyProductionInsertQty(
departmentCode,
machineCode,
operatorCode,
itemNumber,
isKit,
qtyProduced,
inventoryTrxAdapter,
trxScope);
}
inventoryTrxAdapter.CloseConnection();
trxScope.Complete();
}
}
catch (System.Exception ex)
{
successful = false;
MessageBox.Show(ex.ToString());
}
return successful;
}
The isItemNumberKit method
public bool isItemNumberKit(SqlConnection connection, string itemNumber)
{
bool contains;
MessageBox.Show(connection.ConnectionString); // <-- Valid ConnectionString
DataTable dt = getKit(connection, itemNumber); // <-- CULPRIT!
if (dt.Rows.Count > 0)
{
contains = true;
}
else
{
contains = false;
}
return contains;
}
The getKit method
public DataTable getKit(SqlConnection connection, string itemNumber)
{
DataTable dt = new DataTable();
SqlConnection myConnection = connection;
MessageBox.Show(myConnection.ConnectionString); // <-- Valid ConnectionString
SqlParameter paramItemNumber = new SqlParameter();
paramItemNumber.ParameterName = "#ItemNumber";
paramItemNumber.Value = itemNumber;
paramItemNumber.SqlDbType = System.Data.SqlDbType.VarChar;
try
{
using (myConnection)
{
string sql =
#"SELECT kits.Row_Id,
kits.Kit_Item_Number,
kits.Location_Code
FROM Inventory.dbo.Z_PV_Kits kits
WHERE kits.Kit_Item_Number=#ItemNumber";
//myConnection.Open();
using (SqlCommand myCommand = new SqlCommand(sql, myConnection))
{
myCommand.Parameters.Add(paramItemNumber);
SqlDataReader reader = myCommand.ExecuteReader();
dt.Load(reader);
}
}
}
catch (Exception ex)
{
dt = null;
MessageBox.Show(ex.ToString());
}
return dt;
}
When I execute postInventoryData the program throws an exception with the message, "The connectionstring property has not been initialized." with the line numbers pointing to isItemNumberKit and getKit. As you can see in the code above, I used a MessageBox.Show(connection.ConnectionString) throughout the process and each time I received a valid Connection string. I have created a workaround which stores a cached DataTable containing all the kit items I can run linq statements on. I am not in emergency mode or anything but I thought this to be weird and an opportunity for me to learn. Thanks in advance for any help!
It might be possible that you have 2 app.config files in your solution with 2 different connection strings.
OK, I figured it out and now when I think about it the answer was somewhat obvious. I always use using(){} blocks to ensure connections and similar objects are properly disposed and taken care of after they are used. The solution was to simply remove the using(myConnection){} block from the getKit method like this:
public DataTable getKit(SqlConnection connection, string itemNumber)
{
DataTable dt = new DataTable();
SqlConnection myConnection = connection;
MessageBox.Show(myConnection.ConnectionString);
SqlParameter paramItemNumber = new SqlParameter();
paramItemNumber.ParameterName = "#ItemNumber";
paramItemNumber.Value = itemNumber;
paramItemNumber.SqlDbType = System.Data.SqlDbType.VarChar;
try
{
string sql =
#"SELECT kits.Row_Id,
kits.Kit_Item_Number,
kits.Location_Code
FROM Inventory.dbo.Z_PV_Kits kits
WHERE kits.Kit_Item_Number=#ItemNumber
";
//myConnection.Open();
using (SqlCommand myCommand = new SqlCommand(sql, myConnection))
{
myCommand.Parameters.Add(paramItemNumber);
SqlDataReader reader = myCommand.ExecuteReader();
dt.Load(reader);
}
}
catch (Exception ex)
{
dt = null;
MessageBox.Show(ex.ToString());
}
return dt;
}
This will leave the connection intact but properly dispose of the command. Sorry for the long winded question with a short simple answer. Hope this might help someone someday.
I have a problem with the below code,There's no any coding error BUT sometimes it throws some exceptions.I just wanted to know any code organizing issue ? & how to fix it.
Sometimes it shows those exceptions
1.ExecuteReader requires an open and available Connection. The connection's current state is closed.
2.Invalid attempt to call FieldCount when reader is closed.
But Sometimes it works without any issue,as expected
My Coding Goes here
[WebMethod, ScriptMethod]
public static List<HomeImageSliders> GetHomeImageSliders()
{
List<HomeImageSliders> HomeImageList = new List<HomeImageSliders>();
try
{
SqlCommand comHomeImage = new SqlCommand("SP_GetHomeImageSliders", conDB);
comHomeImage.CommandType = CommandType.StoredProcedure;
if (conDB.State != ConnectionState.Open)
{
conDB.Open();
}
SqlDataReader rdr = comHomeImage.ExecuteReader();
DataTable dt = new DataTable();
dt.Load(rdr);
foreach (DataRow r in dt.Rows)
{
HomeImageList.Add(new HomeImageSliders
{
Id = (int)r["Id"],
ImagePath = r["ImagePath"].ToString(),
ModifiedDate = Convert.ToDateTime(r["ModifiedDate"]).Date
});
}
}
catch (Exception ee)
{
}
finally
{
conDB.Close();
}
return HomeImageList;
}
You should use the "using" construction:
(using ommand comHomeImage = new SqlCommand("SP_GetHomeImageSliders", conDB) {
(using SqlDataReader rdr = new SqlDataReader) {
//do some things
}
}
I don't know why your connection sometimes is closed when you call
ExecuteReader()
But why don't you use a using block instead like this:
using(SqlConnection conDB = new SqlConnection(connectionString))
{
...
}
this will close your connection to the DB when it loses scope.
try to prevent using the same connection with two or more threads by usinglock
lock(_conDb)
{
//// your code here
}
and also wrap your conDb in using block as below
using(SqlConnection conDB = new SqlConnection(connectionString))
{
...
}
I am getting Database is locked exception from SQLite for some queries only.
Below is my code:
When I execute any select statement it works fine.
When I am executing any write statement on Jobs Table it also works fine.
This works fine:
ExecuteNonQuery("DELETE FROM Jobs WHERE id=1");
But the same way if I am executing queries for Employees table it is throwing an exception that database is locked.
This throws Exception:
ExecuteNonQuery("DELETE FROM Employees WHERE id=1");
Below are my functions:
public bool OpenConnection()
{
if (Con == null)
{
Con = new SQLiteConnection(ConnectionString);
}
if (Con.State == ConnectionState.Closed)
{
Con.Open();
//Cmd = new SQLiteCommand("PRAGMA FOREIGN_KEYS=ON", Con);
//Cmd.ExecuteNonQuery();
//Cmd.Dispose();
//Cmd=null;
return true;
}
if (IsConnectionBusy())
{
Msg.Log(new Exception("Connection busy"));
}
return false;
}
public Boolean CloseConnection()
{
if (Con != null && Con.State == ConnectionState.Open)
{
if (Cmd != null) Cmd.Dispose();
Cmd = null;
Con.Close();
return true;
}
return false;
}
public Boolean ExecuteNonQuery(string sql)
{
if (sql == null) return false;
try
{
if (!OpenConnection())
return false;
else
{
//Tx = Con.BeginTransaction(IsolationLevel.ReadCommitted);
Cmd = new SQLiteCommand(sql, Con);
Cmd.ExecuteNonQuery();
//Tx.Commit();
return true;
}
}
catch (Exception exception)
{
//Tx.Rollback();
Msg.Log(exception);
return false;
}
finally
{
CloseConnection();
}
}
This is the Exception:
At line 103 : Cmd.ExecuteNonQuery();
Exception Found:
Type: System.Data.SQLite.SQLiteException
Message: database is locked
database is locked
Source: System.Data.SQLite
Stacktrace: at System.Data.SQLite.SQLite3.Step(SQLiteStatement stmt)
at System.Data.SQLite.SQLiteDataReader.NextResult()
at System.Data.SQLite.SQLiteDataReader..ctor(SQLiteCommand cmd, CommandBehavior behave)
at System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
at System.Data.SQLite.SQLiteCommand.ExecuteNonQuery()
at TimeSheet6.DbOp.ExecuteNonQuery(String sql) in d:\Projects\C# Applications\Completed Projects\TimeSheet6\TimeSheet6\DbOp.cs:line 103
Somewhere along the way a connection is getting left open. Get rid of OpenConnection and CloseConnection and change ExecuteNonQuery to this:
using (SQLiteConnection c = new SQLiteConnection(ConnectionString))
{
c.Open();
using (SQLiteCommand cmd = new SQLiteCommand(sql, c))
{
cmd.ExecuteNonQuery();
}
}
Further, change the way you read data to this:
using (SQLiteConnection c = new SQLiteConnection(ConnectionString))
{
c.Open();
using (SQLiteCommand cmd = new SQLiteCommand(sql, c))
{
using (SQLiteDataReader rdr = cmd.ExecuteReader())
{
...
}
}
}
Do not attempt, to manage connection pooling on your own like you are here. First, it's much more complex than what you have coded, but second, it's handled already inside the SQLiteConnection object. Finally, if you're not leveraging using, you're not disposing these objects properly and you end up with issues like what you're seeing now.
You can use 'using' statement as below, that will make sure connection & command disposed correctly even in exception
private static void ExecuteNonQuery(string queryString)
{
using (var connection = new SQLiteConnection(
ConnectionString))
{
using (var command = new SQLiteCommand(queryString, connection))
{
command.Connection.Open();
command.ExecuteNonQuery();
}
}
}
You should close your DataReader before attempting to write any data to the database. Use:
dr.Close();
after you finish using the DataReader.
In my case it was very stupid of me, I was making changes in SQLite browser and did not click on write changes, which locked the DB to be modified by the services. After I clicked the Write changes button, all the post request worked as expected.
A lot of helpful posts here for folks that may have forgotten to clean up a dangling connection, but there is another way this can happen: SQLite does not support concurrent INSERTs; if you issue two INSERTs at the same time the will be processed in serial. When the INSERTs are quick this is fine, but if an INSERT takes longer than the timeout the second INSERT can fail with this message.
I had this happen when I used a long running transaction to accumulate a bunch of INSERTs into one big commit. Basically I locked the database from any other activity during the transaction. Switching to journal_mode=WAL will allow concurrent writes and reads, but not concurrent writes.
I got rid of the long running transaction and let each INSERT autocommit, and that solved my problem.
Mine was caused by not closing a SqliteDataReader when calling HasRows().
I had this:
using (SQLiteConnection connection = new SQLiteConnection(DbPath))
{
connection.Open();
string sql = $"SELECT * FROM ...";
using (SQLiteCommand command = new SQLiteCommand(sql, connection))
{
return command.ExecuteReader().HasRows;
}
connection.Close();
}
But needed to put a using around the ExecuteReader like so:
using (SQLiteDataReader reader = command.ExecuteReader())
{
return command.ExecuteReader().HasRows;
}
Even though the DbConnection was being disposed and re-created each time the db was still being kept locked by the reader.
I was also getting the same error here:
if (new basics.HindiMessageBox(HMsg, HTitle).ShowDialog()==true)
{
SQLiteConnection m_dbConnection = new SQLiteConnection(MainWindow.con);
m_dbConnection.Open();
sql = "DELETE FROM `users` WHERE `id`=" + SelectedUser.Id;
command = new SQLiteCommand(sql, m_dbConnection);
command.ExecuteNonQuery();
m_dbConnection.Close();
LoadUserDG();
}
but when I just changed SQLiteConnection declaration location
public partial class User : Window
{
SQLiteCommand command;
string sql;
AddUser AddUserObj;
List<basics.users> usersList;
basics.users SelectedUser;
SQLiteConnection m_dbConnection;
// ...
private void DeleteBtn_Click(object sender, RoutedEventArgs e)
{
// ...
if (new basics.HindiMessageBox(HMsg, HTitle).ShowDialog()==true)
{
m_dbConnection = new SQLiteConnection(MainWindow.con);
m_dbConnection.Open();
sql = "DELETE FROM `users` WHERE `id`=" + SelectedUser.Id;
command = new SQLiteCommand(sql, m_dbConnection);
command.ExecuteNonQuery();
m_dbConnection.Close();
LoadUserDG();
}
}
Everything is fine now.
I hope this may work for you, too.
If someone can say how this happened, I would like to know the details to improve my knowledge, please.
I had the same issue when loading a lot of data to different tables from multiple threads.
When trying to do the inserts I was getting database locked because the program was doing too many insert too fast and SQLite didn't have time to complete each transaction before another one came.
The insert are done through threading because I didn't want the interface to be locked and wait for the insert to be done.
My solution is to use BlockingCollection with ThreadPool.QueueUserWorkItem.
This allows me to free the interface while doing the inserts.
All the insert are queued and executed in FIFO (First In First Out) order.
Now the database is never locked while doing any SQL transaction from any thread.
public class DatabaseQueueBus
{
private BlockingCollection<TransportBean> _dbQueueBus = new BlockingCollection<TransportBean>(new ConcurrentQueue<TransportBean>());
private CancellationTokenSource __dbQueueBusCancelToken;
public CancellationTokenSource _dbQueueBusCancelToken { get => __dbQueueBusCancelToken; set => __dbQueueBusCancelToken = value; }
public DatabaseQueueBus()
{
_dbQueueBusCancelToken = new CancellationTokenSource();
DatabaseQueue();
}
public void AddJob(TransportBean dto)
{
_dbQueueBus.Add(dto);
}
private void DatabaseQueue()
{
ThreadPool.QueueUserWorkItem((param) =>
{
try
{
do
{
string job = "";
TransportBean dto = _dbQueueBus.Take(_dbQueueBusCancelToken.Token);
try
{
job = (string)dto.DictionaryTransBean["job"];
switch (job)
{
case "SaveClasse":
//Save to table here
break;
case "SaveRegistrant":
//Save Registrant here
break;
}
}
catch (Exception ex)
{//TODO: Handle this exception or not
}
} while (_dbQueueBusCancelToken.Token.IsCancellationRequested != true);
}
catch (OperationCanceledException)
{
}
catch (Exception ex)
{
}
});
}
}
The inserts are done this way, but without the queuing I was still getting the lock issue.
using (SQLiteConnection c = new SQLiteConnection(BaseDal.SQLiteCon))
{
c.Open();
using (SQLiteCommand cmd = new SQLiteCommand(sql, c))
{
cmd.ExecuteNonQuery();
}
c.Close();
}
This one has me stumped. Here are the relative bits of code:
public AgencyDetails(Guid AgencyId)
{
try
{
evgStoredProcedure Procedure = new evgStoredProcedure();
Hashtable commandParameters = new Hashtable();
commandParameters.Add("#AgencyId", AgencyId);
SqlDataReader AppReader = Procedure.ExecuteReaderProcedure("evg_getAgencyDetails", commandParameters);
commandParameters.Clear();
//The following line is where the error is thrown. Errormessage: Invalid attempt to call Read when reader is closed.
while (AppReader.Read())
{
AgencyName = AppReader.GetOrdinal("AgencyName").ToString();
AgencyAddress = AppReader.GetOrdinal("AgencyAddress").ToString();
AgencyCity = AppReader.GetOrdinal("AgencyCity").ToString();
AgencyState = AppReader.GetOrdinal("AgencyState").ToString();
AgencyZip = AppReader.GetOrdinal("AgencyZip").ToString();
AgencyPhone = AppReader.GetOrdinal("AgencyPhone").ToString();
AgencyFax = AppReader.GetOrdinal("AgencyFax").ToString();
}
AppReader.Close();
AppReader.Dispose();
}
catch (Exception ex)
{
throw new Exception("AgencyDetails Constructor: " + ex.Message.ToString());
}
}
And the implementation of ExecuteReaderProcedure:
public SqlDataReader ExecuteReaderProcedure(string ProcedureName, Hashtable Parameters)
{
SqlDataReader returnReader;
using (SqlConnection conn = new SqlConnection(connectionString))
{
try
{
SqlCommand cmd = new SqlCommand(ProcedureName, conn);
SqlParameter param = new SqlParameter();
cmd.CommandType = System.Data.CommandType.StoredProcedure;
foreach (DictionaryEntry keyValue in Parameters)
{
cmd.Parameters.AddWithValue(keyValue.Key.ToString(), keyValue.Value);
}
conn.Open();
returnReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
catch (SqlException e)
{
throw new Exception(e.Message.ToString());
}
}
return returnReader;
}
The connection string is working as other stored procedures in the same class run fine. The only problem seems to be when returning SqlDataReaders from this method! They throw the error message in the title. Any ideas are greatly appreciated! Thanks in advance!
A DataReader is generally connected directly to the database. In this case, when you return from the method, you're returning from inside the using statement that created the SqlConnetion object. That will call Dispose on the SqlConnection, and render the SqlDataReader useless.
Try this:
public SqlDataReader ExecuteReaderProcedure(string ProcedureName, Hashtable Parameters)
{
SqlConnection conn = new SqlConnection(connectionString);
using(SqlCommand cmd = new SqlCommand(ProcedureName, conn))
{
cmd.CommandType = System.Data.CommandType.StoredProcedure;
foreach(DictionaryEntry keyValue in Parameters)
{
cmd.Parameters.AddWithValue(keyValue.Key.ToString(), keyValue.Value);
}
conn.Open();
return cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
}
Call it like this:
public AgencyDetails(Guid AgencyId)
{
evgStoredProcedure Procedure = new evgStoredProcedure();
Hashtable commandParameters = new Hashtable();
commandParameters.Add("#AgencyId", AgencyId);
using(SqlDataReader AppReader =
Procedure.ExecuteReaderProcedure("evg_getAgencyDetails",
commandParameters))
{
commandParameters.Clear();
while(AppReader.Read())
{
AgencyName = AppReader.GetOrdinal("AgencyName").ToString();
AgencyAddress = AppReader.GetOrdinal("AgencyAddress").ToString();
AgencyCity = AppReader.GetOrdinal("AgencyCity").ToString();
AgencyState = AppReader.GetOrdinal("AgencyState").ToString();
AgencyZip = AppReader.GetOrdinal("AgencyZip").ToString();
AgencyPhone = AppReader.GetOrdinal("AgencyPhone").ToString();
AgencyFax = AppReader.GetOrdinal("AgencyFax").ToString();
}
}
}
At the end of the using statement for AppReader, AppReader.Dispose will be called. Since you called ExecuteReader with CommandBehavior.CloseConnection, Disposing of the reader will also close the connection.
Note that I got rid of your bad exception handling as well. Never use ex.Message except possibly for displaying to end-users. Everyone else will want the full exception. Also, no need to print the method name as part of the exception message if you're allowing the full exception to propagate. The method name will be in the stack trace.