I'm working on a WPF application in ADO.NET C#. I'm using a local database to do some test. My question is: Why should I use a Transaction before executing, for example, an UPDATE/INSERT command?
I've tried to do UPDATE and INSERT commands with SqlConnection, SqlCommand, SqlDataAdapter and they work well, even if I've never used a SqlTransaction object on the Connection object. If I do (on a Save Button):
try
{
conn.Open();
SqlTransaction sqlTran = conn.BeginTransaction(IsolationLevel.Serializable);
dAdapter.SelectCommand.Transaction = sqlTran;
dAdapter.Update(dtTable);
sqlTran.Commit();
conn.Close();
}
catch(Exception ex)
{
sqlTran.RollBack();
conn.Close();
}
what are the differences with the same instructions but without the transactions (and Commit/Rollback)?
Related
I migrated my code from WebApi2 to NET5 and now I have a problem when executing a non-query. In the old code I had:
public void CallSp()
{
var connection = dataContext.GetDatabase().Connection;
var initialState = connection.State;
try
{
if (initialState == ConnectionState.Closed)
connection.Open();
connection.Execute("mysp", commandType: CommandType.StoredProcedure);
}
catch
{
throw;
}
finally
{
if (initialState == ConnectionState.Closed)
connection.Close();
}
}
This was working fine. After I migrated the code, I'm getting the following exception:
BeginExecuteNonQuery requires the command to have a transaction when the connection assigned to the command is in a pending local transaction. The Transaction property of the command has not been initialized.
So, just before calling Execute I added:
var ct = dataContext.GetDatabase().CurrentTransaction;
var tr = ct.UnderlyingTransaction;
And passed the transaction to Execute. Alas, CurrentTransaction is null, so the above change can't be used.
So then I tried to create a new transaction by doing:
using var tr = dataContext.GetDatabase.BeginTransaction();
And this second change throws a different exception complaining that SqlConnection cannot use parallel transactions.
So, now I'm in a situation where I originally had no problem to having neither an existing transaction nor can I create a new one.
How can I make Dapper happy again?
How can I make Dapper happy again?
Dapper has no opinion here whatsoever; what is unhappy is your data provider. It sounds like somewhere, somehow, your dataContext has an ADO.NET transaction active on the connection. I can't tell you where, how, or why. But: while a transaction is active on a connection, ADO.NET providers tend to be pretty fussy about having that same transaction explicitly specified on all commands that are executed on the connection. This could be because you are somehow sharing the same connection between multiple threads, or it could simply be that something with the dataContext has an incomplete transaction somewhere.
I'm writing an ASP.NET application. In my datalayer an sql connection is being opened and closed before and after querying. The SqlConnection is being kept as a private field of a single class. Every database call in the class uses the same structure:
conn.Open();
try
{
// database querying here
}
finally
{
conn.Close();
}
Yet, on very rare occasions I get the exception 'The connection was not closed. The connection's current state is open'. It's not possible to reproduce the problem since it originates very rarely from different parts of the code. There is some threading involved in my application but new threads also make new data layer classes and thus new connection objects.
I do not understand how it's possible to have a connection lingering around open using the code above. Shouldn't the connection always be closed after opening, making it impossible for the above exception to occur?
It's likely that an exception is being thrown in the try block that you aren't handling. See this note in MSDN for try-finally:
Within a handled exception, the associated finally block is guaranteed to be run. However, if the exception is unhandled, execution of the finally block is dependent on how the exception unwind operation is triggered.
I would recommend wrapping the connection in a using block anyway:
using (SqlConnection connection = new SqlConnection(connectionString))
{
//etc...
}
Alternatively, add a catch block to the try-finally:
conn.Open();
try
{
}
catch
{
}
finally
{
conn.Close();
}
you should close connections as soon as you operations finished. Try to open connections for the shortest time possible.
However it is best to use using it will call Dispose method even in case of exceptions.
using (SqlConnection conn= new SqlConnection(conStr))
{
//etc...
}
OR
1) Open the connection
2) Access the database
3) Close the connection
//conn.Open();
try
{
conn.Open();
//Your Code
}
finally
{
conn.Close();
conn.Dispose();//Do not call this if you want to reuse the connection
}
I am trying to execute sql inside a transaction using ServiceStack OrmLite. The code below works with Sqlite but not with SqlServer. With SqlServer I get the following error:
ExecuteScalar requires the command to have a transaction when the connection assigned to the command is in a pending local transaction. The Transaction property of the command has not been initialized.
Is there something wrong with this code?
using (var trans = Db.BeginTransaction())
{
try
{
foreach (myObject in myObjects)
Db.Insert<MyObject>(myObject);
trans.Commit();
}
catch (Exception ex)
{
trans.Rollback();
throw ex;
}
}
Someone else put this answer in a comment and then deleted it... so:
BeginTransaction needs to be OpenTransaction
This question has been addressed all over the web and I tried a lot of things without success. The SQL EXPRESS service is setup to accept local system account but the problem still exists.
This is my connection string:
<add name="PhoneTemplateChange" providerName="System.Data.SqlClient" connectionString="Data Source=.\SQLEXPRESS;Database=PhoneTemplateChange;Integrated Security=SSPI" />
I created a class to do database operations in the constructor I have
_connectionString = System.Web.Configuration.WebConfigurationManager.ConnectionStrings["PhoneTemplateChange"].ConnectionString;
and a method in this class to insert data
public void AddNewChangeOrder(int operation, int targetExt)
{
using (SqlConnection con = new SqlConnection(_connectionString))
{
string sql = "INSERT into [dbo].ChangeOrder (operation, targetExt, dtrequested) VALUES (#operation, #targetExt, #dtrequested)";
using (SqlCommand cmd = new SqlCommand(sql))
{
try
{
cmd.Parameters.AddWithValue("#operation", operation);
cmd.Parameters.AddWithValue("#targetExt", targetExt);
cmd.Parameters.AddWithValue("dtrequested", DateTime.Now);
//con.CreateCommand();
con.Open();
//cmd.InitializeLifetimeService();
int rows = cmd.ExecuteNonQuery();
con.Close();
}
catch (SqlException e)
{
throw new Exception(e.Message);
}
}
}
I have played around with the connection string trying all different suggestions, also the commented code in the method above is what I tried to solve the problem. Still no luck!
I also changed the connection string I get two different exceptions this way
Database=PhoneTemplateChange
The above gives the exception in the title.
And the following gives the Exception "Cannot open Database PhoneTemplatechange.mdf requested by the login. Login failed for user 'mydomain\myusername'"
Database=PhoneTemplateChange.mdf
Any ideas?
You are missing the line of code where you specify that cmd uses con as it's connection. As a result the Command (cmd) has no connection, and con isn't associated with any command at all.
Add this line before executing:
cmd.Connection - con;
Alternatively (and better IMO) change your using statement as follows:
using (SqlCommand cmd = new SqlCommand(sql, con))
So, I recently inherited a large project that uses the following data access pattern; unfortunately, this is resulting in a massive number of timeout exceptions related to connection pooling.
Timeout expired. The timeout period elapsed prior to obtaining a
connection from the pool. This may have occurred because all pooled
connections were in use and max pool size was reached"
It clear that the connections are leaking and not getting closed properly.
So, the framework has a DataAccess class with the method GetDataReader.
When the data reader is referenced, it is placed inside a using block, but connections are still leaking.
Does the fact that the connection is not explicitly closed or placed in a using block the reason why the connections are getting leaked?
Normally, I would wrap the connection in a using block AND wrap the data reader in a using block.
Obviously, this framework is very flawed, but would somehow using the option CommandBehavior.CloseConnection for the data reader resolve this issue?
None the external code accesses the SqlConnection directly and has to go through this DataAccess class.
public IDataReader GetDataReader(QueryDto dto)
{
DateTime current = DateTime.Now;
Database db = DatabaseFactory.CreateDatabase(dto.DatabaseName);
DbCommand cmd = db.GetStoredProcCommand(dto.StoredProcedureName);
if (dto.Params.Length > 0)
{
cmd = db.GetStoredProcCommand(dto.StoredProcedureName, dto.Params);
}
dto.Command = cmd;
cmd.CommandTimeout = dto.Timeout;
cmd.Connection = db.CreateConnection();
try
{
cmd.Connection.Open();
}
catch (SqlException ex)
{
// Handle Exception here...
throw;
}
return rdr;
}
Usage in some static repository class:
var query = new QueryDto
{
DatabaseName = "SomeDatabase",
Params = parms,
StoredProcedureName = "StoredProcedureName"
};
using (IDataReader dr = dataAccess.GetDataReader(query))
{
while (dr.Read())
{
// do stuff here
}
}
I think your problem is that the using statement is around a function that has open resources embedded in it. The using will not dispose of the connection that is opened inside GetDataReader. I think your are correct that the Connection itself needs to be in a using block. The using statement only calls Dispose on the object that is passed in, not any nested resources.