Develop Reference

recover "DbContext" lost out after a method

I need your help.
I begin to ASP.net and I fail to retrieve a "dbcontext" to display my request in a "datagrid". Here is my code:
public IQueryable<DiagTab> Clooper(string m_ValEnvoi)
{
string Ladatatable = m_ValEnvoi;
using (var db = new DiagEntities())
{
var secki = db.DiagTabs.Where(Ladatatable); // Ladatatabase = Dynamic LinQ
return secki;
}
I call this way (no error)
TheLoop pilou = new TheLoop();
pilou.Clooper(Valtest);
var olami = pilou.Clooper(Valtest);
but if i try this:
var selection_click = olami;
GridView1.DataSource = selection_click.ToList();
GridView1.DataBind();
the code is interrupted and displays "Could not complete the operation because the DbContext has been deleted".
Is it possible to get the paste has Dbcontext for this request?
thanks for your help

You should call ToList() inside the method, before disposing the DbContext.

Don't use using which dispose the DiagEntities and instead of it, if you want to use it in several methods just declare a property for your DiagEntities in the class constructor.
public IQueryable<DiagTab> Clooper(string m_ValEnvoi)
{
string Ladatatable = m_ValEnvoi;
var secki = db.DiagTabs.Where(Ladatatable); // Ladatatabase = Dynamic LinQ
return secki;
}

Entity set connection timeout

How can I set the value of connectionTimeout (not commandTimeout) of context by coding (not in connection string) ?
This is readonly:
DbContext.Database.Connection.ConnectionTimeout = 10;
Thanks
Udpate:
My probleme is to test if my context is available quickly and the default time is to long ?
I tried this :
int? oldTimeOut = RepositoryDbContext.Database.CommandTimeout;
try
{
RepositoryDbContext.Database.Connection.ConnectionTimeout = 10; //readonly
RepositoryDbContext.Database.CommandTimeout = 10; // doesn't work, the value stay the same
RepositoryDbContext.Database.Connection.Open();
RepositoryDbContext.Database.Connection.Close();
return true;
}
catch
{
return false;
}
finally
{
RepositoryDbContext.Database.CommandTimeout = oldTimeOut;
}
But I can't change the connectionTimeout is readOnly and the commandTimeout doesn't set the value...

I'm not aware of any option to change the connection timeout via the EF API. You can however change the connection string at runtime. You could parse the configured connection string and change the timeout parameter, or add one if it does not exist.
If you are working with SQL Server only, I would suggest using SqlConnectionStringBuilder. Use the constructor that takes an existing connection string, change the ConnectTimeout, get the modified connection string, and use that connection string when constructing your DbContext.
Depending on what you are actually trying to solve, one alternative might be to use SlowCheetah to easily generate the web.config, with different configuration strings, for different build types.
http://visualstudiogallery.msdn.microsoft.com/69023d00-a4f9-4a34-a6cd-7e854ba318b5
UPDATE
Based on your comment...
Try something like
string normalConnectionString = RepositoryDbContext.Database.Connection.ConnectionString;
var connectionBuilder = new SqlConnectionStringBuilder(normalConnectionString);
connectionBuilder.ConnectTimeout = 10;
string testConnectionString = connectionBuilder.ConnectionString;
using (var testRepositoryDbContext = new RepositoryDbContextType(testConnectionString))
{
try
{
testRepositoryDbContext.Database.Connection.Open();
testRepositoryDbContext.Database.Connection.Close();
return true;
}
catch
{
return false;
}
}

Nhibernate transaction locks a tabel

I have developed a WCF api which is using nHibernate. I am new to this. I have used session.update to take care of transaction. I have a for loop in which based on select condition I am updating a record ie. If A is present in tabel1 then I am updating the table else inserting a new entry.
I am getting "could not execute query." when trying to execute a select query on a table which was previously being updated by adding a new entry in the table.
What I think is, because I am using session.save(table1) and then trying select entries from that table I am getting an error. Since session.save temporarily locks the table I am not able to execute a select query on that table.
What can be the solution on this?
Update:
This the for loop I am using to check in the database for some field:
using (ITransaction tranx = session.BeginTransaction())
{
savefunction();
tranx.Commit();
}
Save function:
public void savefunction()
{
for (int i = 0; i < dictionary.Count; i++)
{
ICandidateAttachmentManager candidateAttach = new ManagerFactory().GetCandidateAttachmentManager();
CandidateAttachment attach = new CandidateAttachment();
attach = checkCV();
if(attach == null)
{
//insert new entry into table attach
session.save(attach);
}
}
}
checkCV function:
public void checkCV()
{
using (ICandidateAttachmentManager CandidateAttachmentManager = new ManagerFactory().GetCandidateAttachmentManager())
{
IList<CandidateAttachment> lstCandidateAttachment = CandidateAttachmentManager.GetByfkCandidateId(CandidateId);
if (lstCandidateAttachment.Count > 0)
{
CandidateAttachment attach = lstCandidateAttachment.Where(x => x.CandidateAttachementType.Id.Equals(FileType)).FirstOrDefault();
if (attach != null)
{
return null;
}
else
{
return "some string";
}
}
}
}
What happening here is in the for loop if say for i=2 the attach value comes to null that I am entering new entry into attach table. Then for i=3 when it enters checkCV function I get an error at this line:
IList lstCandidateAttachment =
CandidateAttachmentManager.GetByfkCandidateId(CandidateId);
I think it is because since I am using session.save and then trying to read the tabel contents I am unable to execute the query and table is locked till I commit my session. Between the beginTransaction and commit, the table associated with the object is locked. How can I achieve this? Any Ideas?
Update:
I read up on some of the post. It looks like I need to set isolation level for the transaction. But even after adding it doesn't seem to work. Here is how I tried to inplement it:
using (ITransaction tranx = session.BeginTransaction(IsolationLevel.ReadUncommitted))
{
saveDocument();
}

something I don't understand in your code is where you get your nHibernate session.
Indeed you use
new ManagerFactory().GetCandidateAttachmentManager();
and
using (ICandidateAttachmentManager CandidateAttachmentManager = new ManagerFactory().GetCandidateAttachmentManager())
so your ManagerFactory class provides you the ISession ?
then you do:
CandidateAttachment attach = new CandidateAttachment();
attach = checkCV();
but
checkCV() returns either a null or a string ?
Finally you should never do
Save()
but instead
SaveOrUpdate()
Hope that helps you resolving your issue.
Feel free to give more details

Reading and writing data into sql server simultaneously

I have a service which continuously writes data in a separate thread into SQL database.Now from the same service if i am trying to read from the same table, since i already am writing into it,I get this exception : There is already an open DataReader associated with this Command which must be closed first.
So can anyone help me how to do this simultaneously?
Here s my code for reading data:
public Collection ReadData(string query)
{
{
_result = new Collection<string[]>();
string[] tempResult;
SqlDataReader _readerRead;
using (_command = new SqlCommand(query, _readConnection))
{
_readerRead = _command.ExecuteReader();
while (_readerRead.Read())
{
tempResult = new string[4];
tempResult[0] = _reader[0].ToString();
tempResult[1] = _reader[1].ToString();
tempResult[2] = _reader[2].ToString();
tempResult[3] = _reader[3].ToString();
_result.Add(tempResult);
//Console.WriteLine("Name : {0} Type : {1} Value : {2} timestamp : {3}", _reader[0], _reader[1], _reader[2], _reader[3]);
}
if (_readerRead != null)
{
_readerRead.Close();
}
_readConnection.Close();
return _result;
}
}
}
and here it is for writing to it :
public void WriteData(Collection<TagInfo> tagInfoList)
{
int i = 0;
for (i = 0; i < tagInfoList.Count; i++)
{
using( _command = new SqlCommand(insert statement here)
{
_command.Parameters.AddWithValue("Name", tagInfoList[i].Name);
_command.Parameters.AddWithValue("Type", tagInfoList[i].TagType);
_command.Parameters.AddWithValue("Value", tagInfoList[i].Value);
_reader = _command.ExecuteReader();
if (_reader != null)
{
_reader.Close();
}
}
}
}

You need a different SQLConnection to the database for your writer. You cannot use the same db connection for both.

Although its possible to do, using a separate connection I would question why you need to do this.
If you are reading and writing data to one table in the same service you will be placing unnecessary load on one SQL table, and depending on the number of queries you intend to make this could cause you problems. If you already have this data (in a different thread) why not Marshall the data from the background thread to where you need it as you write it into the database, and you don't need to read the data anymore.
However.... it is difficult to give an fair answer without seeing the code/what you are looking to achieve.

DataReader associated with this Command which must be closed first

I am getting the following error;
"There is already an open DataReader associated with this Command which must be closed first."
is it because I have used the reader in foreach loop ? or what the problem might be ?
Regards
BK
foreach( Apple a in listApple )
{
....
using (SmartSqlReader reader = Db.CurrentDb.ExecuteReader(sp))
{
while (reader.Read())
{
a.blablabla += reader.GetInt32("BLA_BLA_BLA");
}
}
.....
}

Have you implemeneted the SmartSqlReader to close when it's disposed? The regular data readers implement the IDisposable interface and calls Close from the Dispose method.
If you don't close it properly it will keep the Command object occupied until the garbage collector will find the reader and clean it up.

Try the following:
using (SmartSqlReader reader = Db.CurrentDb.ExecuteReader(sp))
{
while (reader.Read())
{
a.blablabla += reader.GetInt32("BLA_BLA_BLA");
}
reader.Close();
}

Add reader.Close() to close the SmartSqlReader