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How to run multiptle queries postgresql statements from C#

I am using EntityFramework and code migrations to keep my Postgres database up to date.
Before deployment on a new environment I would like to make sure the database exists and that the user that will execute queries for the application has enough permissions to do this.
So in short I would like to do the following from my Migrations project before running context.Database.Migrate():
Check whether the database exists
If it doesn't exist create it
Create the user if it doesn't exists
Grant permissions to the user
Run migrations
I have two options (I think):
Run multiple statements at once, keeping the logic inside the query itself and avoid having it in code (C#)
Run statements and deciding in code what to do next.
Option 1 has my preference but when I run the statement checking whether the database exists and create it if it doesn't I get an error: CREATE DATABASE cannot be executed from a function.
The query I'm running looks like this:
DO $$
BEGIN
IF NOT EXISTS(SELECT datname FROM pg_database WHERE datname='database_name') THEN
CREATE DATABASE database_name;
END IF;
END
$$
Option 2 would involve running the statement to check if the database exists with the following code:
using (var conn = new NpgsqlConnection("connection"))
{
conn.Open();
var sql = "SELECT 1 FROM pg_database WHERE datname='database_name'";
var command = new NpgsqlCommand(sql, conn);
var dbExists = command.ExecuteScalar();
if(dbExists == null)
{
command = new NpgsqlCommand("CREATE DATABASE database_name", conn);
command.ExecuteNonQuery();
}
conn.Close();
}
The above code works but I think I prefer option 1.
So I have 2 questions:
How can I fix the CREATE DATABASE cannot be executed from a function error.
Is the second option considered 'wrong'?

Concurrency checks with Entity Framework and Stored Procedures

I am using Entity Framework and manipulating data in a sqlserver database via stored procedures (per client request).
Data is pulled from the database via stored procedures and the results of these stored procedures populates a SQLite db in the Winforms Application.
SQLite is used for additional querying and changing of data and then pushed back via update stored procedure to the sql server db when the user syncs
all stored procedures are on sql server (no in text / in line sql in the application)
I am faced with the scenario where multiple users can potentially attempt to update the same field, which poses 2 problems for me.
If they call the same stored procedure at the same time (select or update).
I am not sure what my options are here from a programming level, I don't have rights to make server changes.
if the field they are trying to update has already been updated.
for problem 2 I am trying to build in a check by date stamping the modification. ie. when a user syncs sql server adds that sync date to a date modified column, if a another user tries to modify the same field i want to check the date modified on his sqlite db and compare that to date modified in sql server, if sql server's date modified is more recent, keep sql server values, if syncing user's modified date is more recent use his...
I have looked into Resolving optimistic concurrency with a condition where the client wins.
using (var context = new BloggingContext())
{
var blog = context.Blogs.Find(1);
blog.Name = "The New ADO.NET Blog";
bool saveFailed;
do
{
saveFailed = false;
try
{
context.SaveChanges();
}
catch (DbUpdateConcurrencyException ex)
{
saveFailed = true;
// Update original values from the database
var entry = ex.Entries.Single();
entry.OriginalValues.SetValues(entry.GetDatabaseValues());
}
} while (saveFailed);
}
but this seems to only work when you directly query the db with Entity Framework and not when you want to update via stored procedure.
what can I use to perform these types of checks?

Ok, This is probably not the best solution, but it is what I was able to come up with, and although not tested extensively initial once over seems to be ok-ish.
I am not going to mark this as the answer, but its what i got working based on my question above.
calling stored procedure at same time, created a class for the transactions
public class TransactionUtils
{
public static TransactionScope CreateTransactionScope()
{
var transactionOptions = new TransactionOptions();
transactionOptions.IsolationLevel = IsolationLevel.ReadCommitted;
transactionOptions.Timeout = TransactionManager.DefaultTimeout;
return new TransactionScope(TransactionScopeOption.Required, transactionOptions);
}
}
and then in code use it as follows:
var newTransactionScope = TransactionUtils.CreateTransactionScope();
try
{
using (newTransactionScope)
{
using (var dbContextTransaction = db_context.Database.BeginTransaction(/*System.Data.IsolationLevel.ReadCommitted*/))
{
try
{
db_context.Database.CommandTimeout = 3600;
db_context.Database.SqlQuery<UpdateData>("UpdateProc #Param1, #Param2, #Param3, #Param4, #Param5, #Param6, #DateModified",
new SqlParameter("Param1", test1),
new SqlParameter("Param2", test2),
new SqlParameter("Param3", test3),
new SqlParameter("Param4", test4),
new SqlParameter("Param6", test5),
new SqlParameter("DateModified", DateTime.Now)).ToList();
dbContextTransaction.Commit();
}
catch (TransactionAbortedException ex)
{
dbContextTransaction.Rollback();
throw;
}
As for issue 2 (concurrency)
I could not find a way to use built in concurrency checks between data on SQL Server and the data that I want to update from SQLite (2 different contexts)
So I am storing Date modified in both sql server and sqlite.
the sqlite date modified is updated when the user modifies a record,
date modified on sql server is updated when a sync runs.
Before syncing I query the sqlServer db for the record to be updated's date modified and compare it with the sqlite's date modified for that record in a if statement and then either run the update stored procedure for that record or not

Unable to begin a distributed transaction using Entiy Framework

I'm having the following error executing this piece of code:
private bool _updateList(SysInfo _sysInfo, List<pList> _pList)
{
try
{
foreach (var p in _pList)
{
_context.spUpdatePListApprovalFlow(p.countryID, _sysInfo.User.JobRoleID, p.src, p.id, p.status, _sysInfo.User.Username);
}
return true;
}
catch (Exception ex) //debug only
{
throw; //throws error to the main try catch
}
}
ERROR
The operation could not be performed because OLE DB provider "MSDASQL"
for linked server "AS400_LINKEDSRV" was unable to begin a distributed
transaction.
However, everything works fine when I run the Stored Procedure in SQL Management Studio:
exec [dbo].[spUpdatePListApprovalFlow]
#CountryID = 123456,
#UserTypeID = 23456,
#Src = 1,
#Id = '123456789',
#Status = 30,
#Username = 'username'
I'm tired of digging for an answer nothing works... Few things I've tried:
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
insert multiple transactions in the stored procedure
This sp has 2 sub stored procedures on it. One that writes into a table of the application's database, and another that updates a table in as400.

In EF6 stored procedures are called in an explicit transaction, by default. You can turn this off for a particular DbContext instance by changing its configuration after creating it, or for all instances of a DbContext type by changing it in the constructor. EG
using (var db = new Db())
{
db.Configuration.EnsureTransactionsForFunctionsAndCommands = false;
//. . .
}
See: https://msdn.microsoft.com/en-us/library/system.data.entity.infrastructure.dbcontextconfiguration.ensuretransactionsforfunctionsandcommands

Ok, after half a day trying to solve this I've finally solved it.
Resolution
Downgraded from Entity Framework 6 to Entity Framework 5 and the
distribuited transactions error has gone.
Just pay attention, if you're going to do this, you have to change some usings in your code. ( in auto generated code in the Data Model as well)
EF 6 uses
using System.Data.Entity.Core.Objects
EF 5 uses
using System.Data.Objects;

If you don't need distributed transactions you can try to disable them in the settings of the linked server:
EXEC master.dbo.sp_serveroption
#server=N'AS400_LINKEDSRV',
#optname=N'remote proc transaction promotion',
#optvalue=N'false'

Refer to this Microsoft page on Linked Servers.
Your System Administrator and/or DBA will probably need to make changes to address the missing linked server definition to your AS/400 server.
Another possible issue is that the AS/400 server (from IBM) lacks software support for the OLE DB data sources. This too would be something that the System Administration staff may need to address.

Using EF transaction across libraries

I have this class A that begins an EF transaction where UserDb is my DbContext
using (DbContextTransaction dbTransaction = UserDb.Database.BeginTransaction(IsolationLevel.ReadUncommitted))
Then I have several inserts and there is a need to call another library [which essentially lives on the same server in the bin folder] to do another insert.
new ExtLibrary().CreatePoweruser(3, UserDb);
As you can see I am passing the same connection. And this statement is within the top using which I thought would mean that everythign is in the same transaction.
Extlibrary code:
Data.Entities.User UserEntity = new Data.Entities.User {
UserTypeId =34,
CreatedDate = DateTime.Now,
CreatedBy = "mk92Test",
};
UserDb.Users.Add(UserEntity);
UserDb.SaveChanges();
Everything works unless the ExtLibrary insert fails. Control comes back to the parent class which has rollback code on exception and I get an The underlying provider failed on rollback. But the first set of inserts certainly do rollback even after this exception.
Please advise.

SqLite in memory database : CREATE TABLE does not work?

When using this code on a SqLite file database, it works fine.
using (var ctx = new Test2010Entities())
{
string s = "CREATE TABLE 'Company' ([Id] integer PRIMARY KEY AUTOINCREMENT NOT NULL, varchar(50) NOT NULL);";
ctx.ExecuteStoreCommand(s);
ctx.Companies.AddObject(new Company { Code = "_1" });
ctx.Companies.AddObject(new Company { Code = "_2" });
ctx.SaveChanges();
foreach (var c in ctx.Companies.ToList())
{
Console.WriteLine(c.Code);
}
}
But when runnning this code on a SqLite 'In Memory' database (Data Source=:memory:;Version=3;New=True;) , I get this exception:
Unhandled Exception: System.Data.UpdateException: An error occurred
while updating the entries. See the inner exception for details. --->
System.Data.SQLite.SQLiteException: SQL logic error or missing
database no such table: Company
Note this is tested with VS 2010, EF 4.4.0.0 and sqlite-netFx40-setup-bundle-x86-2010-1.0.84.0
::: UPDATE :::
As Simon Svensson suggested, opening the connection before any other commands does do the trick:
ctx.Connection.Open();

This happens when your ORM closes your connection, and reopens it. That will reset the sqlite in-memory database to its default state; i.e. empty.
The same thing happens with NHibernate unless you set connection.release_mode = close (the default is after_transaction.
I'm not familiar with Entity Framework, but I expect a similar setting or using the DataContext(IDbConnection) constructor which is documented as "If you provide an open connection, the DataContext will not close it."
The same documentation also states "In a System.Transactions transaction, a DataContext will not open or close a connection to avoid promotion." which may be a cleaner solution.
Using some Reflector magic shows that it's SQLiteConnection.Open that calls (via SQLite3.Open) sqlite3_open_interop (if you're using the NuGet sqlite package). This shows that you get a new empty in-memory database everytime you call SQLiteConnection.Open.