I am working on a small application that is using Linq-to-SQL to access a SQL Server database. The requirement is to write tests using SQL Server CE to test the application.
In the past, I created tests using SQL Server CE with Entity Framework and it's straight forward due to support of SQL Server CE in Entity Framework that allows .sdf file creation based on the entities.
Is there any way to achieve the same for Linq-to-SQL, too? To be very specific, I want to achieve something like this using Linq-to-SQL:
System.Data.Entity.Database.DefaultConnectionFactory =
new SqlCeConnectionFactory("System.Data.SqlServerCe.4.0");
using (var sqlCeContext = new EntityFrameworkContext())
{
sqlCeContext.Database.Create();
}
Yes, the DataContext class has a CreateDabase method, that you can use. http://msdn.microsoft.com/en-us/library/system.data.linq.datacontext.aspx
Related
I am developing an application in which the database is selected by the end user at runtime. The database can either be on a MS SQL server or an IBM DB2 server. I am currently using IBM DB2 10 Express-c on a windows server for testing. I am developing using Visual Studio 2013 C# and Entity Framework 6. I have installed the EntityFramework.IBM.DB2 Nuget package for the DB2 support. I am using reverse-engineer code-first against an existing SQL server database to generate my base code. The application works fine against a SQL Server database.
I am using System.Data.Common.DbProviderFactories.GetFactory to generate the provider.
System.Data.EntityClient.EntityConnectionStringBuilder connectString = new System.Data.EntityClient.EntityConnectionStringBuilder(a_Connection);
System.Data.Common.DbConnection conn = System.Data.Common.DbProviderFactories.GetFactory(connectString.Provider).CreateConnection();
conn.ConnectionString = connectString.ProviderConnectionString;
LB500Database = new LB402_TestContext(conn, true);
a_Connection is provider=IBM.Data.DB2;provider connection string="Database=LISTBILL;User ID=xxxx;Password=yyyy;Server=db210:50000"
and is being parsed correctly by the EntityConnectionStringBuilder.
I then try to access a table in the database with
LBData500.LB_System oneSystem;
System.Linq.IQueryable<LB_System> allSystem = LB500Database.LB_System.Where(g => g.DatabaseVersion == databaseVersion && g.CompanyID == companyID);
I get an invalid operation exception "Sequence contains no matching element" which means that no elements are returned. If I remove the Where so that all rows are returned (there is one in the table) and try to enumerate the result set using the VS debugger I see the message:
"The context cannot be used while the model is being created. This exception may be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. Note that instance members of DbContext and related classes are not guaranteed to be thread safe."
I am not using multi-threading. I am not inside the OnModelCreating.
Just changing the connect string to point to SQL server works fine, so I think my basic approach is sound. If I were getting some kind of error back from the server I would have something to go on. I can run the query from inside Visual Studio, so I have connectivity.
Any pointers would be appreciated.
UPDATE:
I turns out the EF objects were generated using EF5 and the EF6 runtime was being used. I regenerated the EF objects using EF6 reverse engineer code first. I can now connect to the database and get an error message:
"ERROR [42704] [IBM][DB2/NT64] SQL0204N \"DBO.LB_SYSTEM\" is an undefined name."
The schema in the DB2 database is the same as my userid (in this case, not always). I added the CurrentSchema=xxxx to the provide connection string, but EF is still passing dbo as the schema name.
Now I need a way to change the schema name at run time. I saw a link to codeplex EFModelAdapter (http://efmodeladapter.codeplex.com). So I may give that a try.
Update2 After looking through EFModelAdapter, I decided to take a different route. Since I only need database access and not schema management, I decided to go with Dapper (https://github.com/StackExchange/dapper-dot-net). This works great for what I need and allows me to change the schema name when accessing DB2 databases.
As per my Update 2, Entity Framework was a little overkill for what I needed. I switched to dapper https://github.com/StackExchange/dapper-dot-net and I am working fine against multiple DBMSs.
Hey I have a unique and troubling situation.
I am working on a project where my team has used a mixture of Enterprise Data Library plus Entity Framework. Obviously this probably not recommended but it is what I'm stuck with. I would like to take a method written using Enterprise Data Library and also take a different method written using Entity Framework, and wrap both of these methods in a single transaction (without requiring Microsoft Distributed Transaction Service). I'm hoping to minimize rewriting code and be able to wrap the two methods in a single transaction just as they are. Is this possible? Thanks.
Using SQL Server 2008 and .NET 4.0
I suppose you want to mix EF and EntLib queries in the same TransactionScope, without using DTC.
Good news: it's possible. If you use exactly the same connection string for EntLib DAAB and EF DbContext, it will work, depending on the versions of EF, EntLib and SQL Server.
So what you have to do is:
check you have the right versions
get the version of your connection string changed by EF and use it instead of yours.
For 1, I have checked these combinations:
SQL Server must be 2008 or older
EntLib 4.1 + EF 5 doesn't work
EntLib 5 + EF 5 works
For 2, to get the connection string changed by EF you have to debug the execution of code that uses an instance of a DbContext. Set a breakpoint and watch or inspect the DbContext Database.Connection.ConnectionString property. That's the EF version of your connection string. Use it for both EF and EntLib and you'll get rid of DTC.
In this forum here , someone mentions that Entity Framework does not work with Access (Jet DB - .mdb). However it seems that there is a provider for Jet DB as described here
Which makes me think that the only thing I need with Entity Framework is to define the follwing before I define the models:
<connectionStrings>
<add name="ProductContext"
providerName="Microsoft.Jet.OLEDB.4.0"
connectionString="Source=C:\mydatabase.mdb;Jet OLEDB:Database
Password=MyDbPassword;"/>
</connectionStrings>
Does anyone know if Entity Framework works fine with Jet DB, I want to make sure it does before I start since my design document depends on this fact.
Thanks
Entity Framework does not support OLEDB connections, so your connection string will not work. It is practically impossible to get Entity Framework to collaborate with MS Access. You will either need to dump the MS Access part of your design, or the Entity Framework part.
The closest you could get using MS Access is using strongly typed datasets and Linq-to-DataSet http://msdn.microsoft.com/en-us/library/bb386977.aspx
Or, considering going with SQL Express instead (it's free) http://www.microsoft.com/sqlserver/en/us/editions/2012-editions/express.aspx
There is a MS Access EF 6.1 provider here
https://jetentityframeworkprovider.codeplex.com/
EDIT
Now the EF provider for Access is hosted on GitHub
https://github.com/bubibubi/JetEntityFrameworkProvider
This problem is not readily reproducible in a simple example here but was wondering if anyone has any experience and tips, here is the issue:
using Entity Framework
have many points in application where (1) data is written to some entity table e.g. Customer, (2) data is written to history table
both of these actions use Entity Framework, HOWEVER, they use different contexts
these actions need to be both in one transaction: i.e. if one fails to write, the other should not write, etc.
I can wrap them with a TransactionScope,
like this:
using (TransactionScope txScope = new TransactionScope()) {
...
}
but this gives me:
Microsoft Distributed Transaction Coordinator (MSDTC) is disabled for
network transactions.
Our database admin has told me that MSDTC is disabled by choice and can not be installed.
Hence I am making changes trying to create my own EntityConnection with a MetadataWorkspace with the idea that each context will use the same EntityConnection. However, this is proving near impossible trying to get it to work, e.g. currently I continue to get the above error even though theoretically both contexts are using EntityConnection. It's difficult to understand where/why Entity Framework is requiring the MSDTC for example.
Has anyone gone down this road before, have experience or code examples to share?
Well, the problem is quite easy.
If you are using sql server 2008 you should not have that problem because you have promotable transaction, and as .NET knows that you are using the same persistence store (the database) it wont promote it to DTC and commit it as local. look into promotable transaction with sql server 2008.
As far as I know Oracle is working in its driver to support promotable transactions, but I do not know the state, MS oracle driver does not support it.
http://www.oracle.com/technology/tech/windows/odpnet/col/odp.net_11.1.0.7.20_twp.pdf
If you are using a driver that do not support promotable transactions it is impossible for .NET to use local transaction doing two connections. You should change your architecture or convince the database admin for installing MSDTC.
I had a similar problem with SQL 2008, Entity Framework.
I had two frameworks defined (EF1, and EF2) but using identical connection strings to a sql 2008 database.
I got the MSDTC error above, when using nested "usings" across both.
eg the code was like this:
using (TransactionScope dbContext = new TransactionScope())
{
using (EF1 context = new EF1())
{
// do some EF1 db call
using (EF2 context2 = new EF2())
{
// do some EF2 db call
}
}
dbContext.Complete();
}
It wasnt as simple as this, because it was split across several methods, but this was the basic structure of "usings".
The fix was to only open one using at a time. No MTDSC error, No need to open distributed transactions on db.
using (TransactionScope dbContext = new TransactionScope())
{
using (EF1 context = new EF1())
{
// do some EF1 db call
}
using (EF2 context2 = new EF2())
{
// do some EF2 db call
}
dbContext.Complete();
}
I think that what you need to do is to force your contexts to share single database connection. You will be able then to perform these two operations against two different contexts in single transaction. You can achieve this by passing one EntityConnection object to both of your context's constructors. Of course this approach will require you to pass this object to methods which update DB.
I have recently blogged about creating database context scope which will make using multiple EF contexts and transactions easier.
The title sums up my problem. I start from an empty model in VS2010 beta2, and then choose to generate my database from model, i then choose to create a new SQL CE database. Up until that moment everything runs fine. EF generates some SQL and saves it as MyModel.emdx.sql. Here comes the problem, the generated SQL can't be executed on the CE database and throws a couple error messages, like 'ALTER TABLE is not supported' and some others.
I reckon there is no way to do Model first with an SQL CE database, so I'm back to the Database first approach. Or has anyone managed to sucessfully generate an SQL CE database from the edmx model in VS2010?
I just ran a MyModel.edmx.sql script against an SQL CE database and it executed without error. I used VS 2010 RC, so I suspect the problem you encountered was related to the Beta 2 release. I conclude that the problem was fixed in the RC
When you first Generate Database from Model..., you will create a connection in App.Config. If you initially created a non-CE connection, you will generate non-CE SQL, and it will get a .sql extension as you described (if your connection is to CE, you will get a .sqlce extension on the DDL file).
You need to delete the connectionstring from App.Config, and maybe the datasource from Project -> Properties -> DataSources. Then when you choose Generate Database from Model... it will ask to create a new connection, and you can choose a CE connection instead of a server one.