I've got a parameters table where I've got a parameter to say whether my program should run, I'm trying to get this value to check for a function.
Here is the function
private static bool shouldRun()
{
OracleCommand c = conn.CreateCommand();
c.CommandText = "select value from parameters where lower(name) = lower('valuetocheck')"; // this one doesn't work
//c.CommandText = "select 'Y' from dual"; - This one works
c.CommandType = System.Data.CommandType.Text;
OracleDataReader dr = c.ExecuteReader();
dr.Read();
string s = dr.GetString(0); // exception on this line
return false;
}
The additional information is below:
Invalid operation on a closed object
I've tried selecting from dual, as you can see above, which works perfectly fine, but when I try to run the actual query it doesn't like it. I've checked the query in SQL Developer and it works fine.
I've had a look around SO and other websites and the only information I could get on this issue was that the command wasn't associated with a connection, which as you can see above it is.
I've also tried just doing
OracleCommand c;
c.Connection = conn;
Which also doesn't work.
Any insight into this would be great, thanks!
I had the same issue recently. I got the "Invalid Operation on a closed object" but when I debug the code, it was the OracleDataReader that was closed and not the OracleConnection. My problem was the query retuned an empty response and the DataReader closes itself if there is no data. So my resolution was simply checking if the data reader have any rows by adding the following..
dro.Read();
if (dro.HasRows)
{
//Do your
}
I hope it helps someone.
When Oracle gives this error - "Invalid Operation on a closed object", more often than not, what actually happens is that the user does not have access privileges to the objects they are trying to access in the database. Check your connection string and make absolutely sure that the user listed in that connection string does have privileges to the objects in your query - in this case, read access to the Parameters table.
NOTE: While the information in this answer does not directly fix the issue in the original question, I found this question and the other answers very helpful in pinpointing the solution to another related scenario.
When changing from the unmanaged Oracle.DataAccess library to the managed Oracle.ManagedDataAccess library, we found a very tricky difference. Apparently, with the unmanaged library, the dr.Read() call is not required for the fetch to happen, but it most definitely is required with the managed library.
After switching to the managed library, all of our calls constructed similar to the example in the question needed to have dr.Read() added before trying to get any data out of the dr object, otherwise we would get the same "Invalid operation on a closed object" message.
Check your connection String
Replace conn.State == ConnectionState.Closed with conn.State != ConnectionState.open
For me the issue was in this part of my code -
(dt is the object of DataTable in the below code samples)
using (var reader = lSqlCommand.ExecuteReader())
{
while (reader.Read())
{
dt.Load(reader);
}
}
When I removed the while part it got resolved. The working part now is like -
using (var reader = lSqlCommand.ExecuteReader())
{
dt.Load(reader);
}
Related
I have a piece of code that I reuse that helps me connect to an adt database and read the data.
using Advantage.Data.Provider;
...
protected DataTable FillTable(string tableName)
{
DataTable table = new DataTable();
using (var conn = new AdsConnection(connectionString))
using (var adapter = new AdsDataAdapter())
using (var cmd = new AdsCommand())
{
cmd.Connection = conn;
cmd.CommandText = "select * from " + tableName;
adapter.SelectCommand = cmd;
conn.Open();
adapter.Fill(table);
conn.Close();
}
return table;
}
This code works perfectly the first time I go through it, but gives the following exception the second time I call it with a different table name.
System.EntryPointNotFoundException: 'Unable to find an entry point named 'AdsIsConnectionAlive' in DLL 'ace32.dll'.'
I would like an explanation.
I've tried to read up on this error, but all the possible scenario's I've found don't explain why it works the first time. They mention problems with the DLL like it being the wrong version or some incompatability with the .NET version, ...
If I change the order of the calls the code still fails on the second time, so I know the problem isn't with the name of the table or the way I call my code. The problem is probably with me not closing the connection correctly. I've tried adding more braces just to make sure that that part runs correctly and I've debugged to make sure that the first conn.Close(); is executed correctly.
I could place all my code within this code and only use one connection that I keep open as long as I need it. That would bypass my problem, but I would like to avoid that and to understand what I'm doing wrong.
This is most likely caused by loading an older version of ace32.dll from a newer version of the ado.net components. The AdsIsConnectionAlive was introduced in a later version of the DLL - not sure about the exact version probably 6.0 or later.
The first time the connection was made, the ado.net component knows that the connection was not alive so there was no need to call the IsAlive entry point. The second time around, since there was already a connection made to the same connection path, it would try to reuse it by checking to see if it is still alive. I think that there is a way to disable the connection caching but do not remember the detail. A better solution would be to make sure that the advantage DLLs are matching version.
I'm using Oracle.ManagedDataAccess Nuget package version 18.3.0. I tried many things. I tried to dispose everything I can think of, even oracle parameters objects. And wrapped everything inside a using block but to no avail. The only thing that actually worked for me is that the commented line OracleConnection.ClearPool(oracle);. Is this a bug, or some configuration related issue, or am I misunderstand things here? Also, I tried to remove the reference of Oracle.ManagedDataAccess and replaced it with a reference to System.Data.OracleClient and that actually worked for me. It automatically closed the connection, so no connection left with "In-Active" status. The code below I moved it into a simple, single button, Windows Forms application to make 100% sure nothing is interfering and the problem still occurring.
using (var oracle = new OracleConnection("Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=SomePortHere))(CONNECT_DATA=(SERVER=SHARED)(SERVICE_NAME=anotherHost)))", new OracleCredential(userName,password)))
{
oracle.Open();
using (var command = new OracleCommand())
{
var query = "SELECT x from y where z=:param1";
command.Connection = oracle;
command.CommandText = query;
command.CommandType = System.Data.CommandType.Text;
var param1 = new OracleParameter(":param1", xyz);
command.Parameters.Add(param1);
using (var reader = command.ExecuteReader())
{
if (reader.Read())
{
//read the data from the reader
}
}
param1.Dispose();
}
//If this line is commented, there will be a connection left open, with InActive status
//OracleConnection.ClearPool(oracle);
}
password.Dispose();
return myData;
And this is an image to show the opened connection through Toad.
Of course, for each click to that button, the code above will execute and a new session will remain open, until what you see in the image.
The name "TheTesterOfAllTests.exe" is the Windows Forms app.
Is this a configuration problem?
Is there any way to solve this issue other than using ClearPool method? Because it affects the performance of the app.
P.S. The application that is originally using the code above is a WCF Service that is consumed by a Web application.
P.S. 2 There is some kind of memory leakage, with each click to that button the memory usage increases
I ran into the same problem.
I solved it by changing the initialization of the OracleConnection.
from
var con = new OracleConnection(
"Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=SomePortHere))(CONNECT_DATA=(SERVER=SHARED)(SERVICE_NAME=anotherHost)))",
new OracleCredential(userName,password));
to
var con = new OracleConnection(
"USER ID=myuser;PASSWORD=mypwd;Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=SomePortHere))(CONNECT_DATA=(SERVER=SHARED)(SERVICE_NAME=anotherHost)))");
To me, this different behavior looks like a bug.
As a result, i can no longer use OracleCredential and must store the password as a string. That's okay for me.
remark: SecureString shouldn't be used
It turns out the problem is in the way internally oracle creates connection, since for each newly created OracleConnection object, a new Connection is added to the Connection pool. I counted 91 connection entry in the connection pool.
The solution was to use one OracleConnection instance for each request "Per Request Scope". I implemented that by using a simple generic IDatabase<TConnection> interface with one TConnection GetConnection<TConnection>() method and of course for each method that will be called on that same request's instance, a pair of Open/Close call will take place so we don't keep the connection open the whole time.
Regarding the memory leak, I'm still not able to 100% confirm this, but when I used the Oracle.DataAccess.Client library instead of Oracle.ManagedDataAccess the memory usage reduced dramatically. So, I switched back to Oracle.DataAccess.Client.
P.S. I will update this answer in case of new information regarding these two issues, and contributions are very welcome, maybe I misunderstand something regarding how Oracle deals with the database connection.
I searched and checked but did not see what I need. I am using a data adapter's UpdateCommand's ExecuteNonQuery to update a local Access database. When I run the code, the ExecuteNonQuery does not appear to finish before the next line of code is executed and therefore, the updated database is not reflected in my grid or my text boxes. If I put a messagbox right after the ExecuteNonQuery, then when I hit ok in the messagebox, the rest of the code is executed and the updated database is reflected in my grid and text boxes. Or if I step through the code in debug without the messagebox to hault execution, the update to the database is reflected on my form. But if I just run the code without something after the query to slow it down or stop it, the update is not shown in my controls.
OleDbConnection connection = new OleDbConnection(connString);
string sql = "Update Table1 set Country = '" + txtNewText.Text + "' where SomeNum =
1111";
connection.Open();
dAdapter.UpdateCommand = connection.CreateCommand();
dAdapter.UpdateCommand.CommandText = sql;
dAdapter.UpdateCommand.ExecuteNonQuery();
//MessageBox.Show("Pause");
dTable.Clear(); //Clear or it will add everything to what was there.
dAdapter.Fill(dTable);
row = dTable.Rows[0];
txtCompany.Text = row["Name"].ToString();
txtGenre.Text = row["Job"].ToString();
txtId.Text = row["Id"].ToString();
txtSomeNum.Text = row["SomeNum"].ToString();
txtCountry.Text = row["Country"].ToString();
I'm assuming that the update query is not finishing before I re-fill the data table. Can someone please help me with this. I looked for something to show the status of the update query but did not see what I need. What am I missing here???
Thank you!
VH
10/28/14 Last night I added dAdapter.UpdateCommand.ExecuteNonQuery() right after dAdapter.UpdateCommand.ExecuteNonQuery(); then everything worked. I was not sure if this was just something that took enough time to allow the query to finish and therefore causing the update to display, or if it was just some fluke "band-aide" that worked. I then replaced that with connection.Close(); and that worked as well. Again...I don't know if closing the connection caused the query to finish and the connection to close before moving to the next line of code, or if this was also just "fudging" it to work. I have seen other people having similar problems in my searching for answers but I have not seen any one explain what the problem is and why this happens or the most appropriate solution.
You should use the OleDbDataReader, since you aren't using SQL.
Provides a way of reading a forward-only stream of data rows from a data source.
An example:
using (OleDbConnection connection = new OleDbConnection(connectionString))
{
OleDbCommand command = new OleDbCommand(queryString, connection);
connection.Open();
OleDbDataReader reader = command.ExecuteReader();
while (reader.Read())
{
Console.WriteLine(reader[0].ToString());
}
reader.Close();
}
This will iterate through each specified column allowing you to fill your data. Documentation can be found here.
I have created a query which is: SELECT Replace(column_name,a,b) AS expr1
FROM table1; the name of this query is:filepath.
I have wrote the following code in C#. when i compile the code it Syntax error in PROCEDURE clause.
OleDbCommand cmd1 = new OleDbCommand();
cmd1.Connection= ren_connection1;
cmd1.CommandType = CommandType.Text;
cmd1.CommandText = "Execute filepath";
OleDbParameter oldfilevalue = new OleDbParameter();
oldfilevalue.ParameterName = "a";
oldfilevalue.OleDbType = OleDbType.VarChar;
oldfilevalue.Direction = ParameterDirection.Input;
oldfilevalue.Value = oldname2;
OleDbParameter newfilevalue = new OleDbParameter();
newfilevalue.ParameterName = "b";
newfilevalue.OleDbType = OleDbType.VarChar;
newfilevalue.Direction = ParameterDirection.Input;
newfilevalue.Value = oldname1;
cmd1.Parameters.Add(oldfilevalue);
cmd1.Parameters.Add(newfilevalue);
i = cmd1.ExecuteNonQuery();
//oldefile value can be like this: D:/myfile/pictures/cars/
//newfile value can be like this: D:/myfile/pictures/jeeps/
i want to replace in a row a string with another string without modifying the whole row..and i thought replace will work but it didnt :(
access version is:2007.
any idea or help will be greatly appreciated.
Thanks alot.
I am afraid Replace is only available if you are running within Access, as Vincent mentions, it is a VBA function, not a Jet/ACE function. Also discussed: Exception when trying to execute "REPLACE" against MS Access. I have replied to what i think is your first question, update table access, with a possible solution.
Try changing your commandtext with
cmd1.CommandText = "EXECUTE yourProcedureName";
Edit now that your procedure is invoked correctly you need to work around the missing "Replace" function (btw, have you tried Vincent Vancalbergh's suggestion to see if "Replace can be made to work? That would be much easier....)
What I was saying in the comments is that you could select the content of the table, perform the replace in c# code and (if needed) update your table with the new values.
your select becomes:
SELECT table1_id, column_name FROM table1;
and your code changes like this:
//you should change ExecuteNonQuery to ExecuteReader, since you want
// to read the results of your SELECT
OleDbDataReader rdr= cmd1.ExecuteReader();
//Iterate through the table
while(rdr.Read())
{
string currentValue=rdr["column_name"].ToString();
string newValue = currentValue.Replace(a, b);
//now do what you need with the row
// ...
}
I found the following here:
Prior to a company wide upgrade to XP
there was no problem with access
databases, so I am not sure if this
would be a solution to your issue. But
I had a problem similar to yours after
an upgrade to XP from 2000 with some
access databases. Undefined Function
"Replace" errors started to pop up. At
the end of the day it turned out to be
the version of VBA installed. 6.0
versus 6.3. The problem machines had
6.0 installed. Start access Help -> About MS Access -> SYSTEM INFO ->
APPLICATIONS -> Microsoft Access 2000
-> SUMMARY. The VBA version of 6.00 produced the error, VBA version 6.03
no problem. Take Care, Nick
Now the question is, what VBA version are you using?
The solution is in #onedaywhen's answer her:
Exception when trying to execute "REPLACE" against MS Access
It uses Mid(), Len() and InStr() in place of Replace().
Im having trouble with a stored procedure, I can't commit after I execute it.
Its showing this error "[System.Data.Odbc.OdbcException] = {"ERROR [HY000] [MySQL][ODBC 5.1 Driver]Commands out of sync; you can't run this command now"}"
The SP by itself works fine.
does anyone have idea of what might be happening?
thanks.
UPDATE: in C# I wasn't closing the reader before commiting.
OdbcDataReader reader = cmd.ExecuteReader();
if (reader.Read())
{
result = Convert.ToBoolean(reader[0]);
}
reader.Close(); //this line was not here when I had the error
cmd.Transaction.Commit();
I found out what the problem was, I removed select vExito; from the stored procedure and now it works.
i'm just going to erease that since its of no use. was like that because it did something else before and we didn't want to change the .net code, but I guess it must be done.
UPDATE:
Also I wasn't closing the reader, when I closed it, it worked; >_>