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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

How to read External Sqllite Database in xamirin android in Visual Studio C#

My Code :
var dbpath = Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), "ot.db3");
Context myContext = null;
try
{
var dbcon = new SQLiteConnection(dbpath);
var db= dbcon.Query<records>("SELECT * FROM records WHERE sno = ? ", "1");
int count = db.Count;
}
catch (IOException ex)
{
var reason = string.Format("The database failed to create - reason {0}", ex.Message);
Toast.MakeText(myContext, reason, ToastLength.Long).Show();
}
I Create a Sqlite Database from my SQL Server Database.
Now I save it to my Phone on this path (Android/Data/Application/File)
Now using Sqlite-net-pcl nugget package for Sqlite Connection the connection works fine showing have no error.
When I try to read a table from database this Give any error that "No Such Table exist in database". And the table exists in the database and is populated with data.
What can I do?
Thanks in advance

Why are you writing the SQL query? You could make it more simple, something like, conn.Get(id);
You will only need to add [PrimaryKey] to your PK in the model.
Also, I suggest you to not use SQLite.SQLiteConnection and use SQLiteAsyncConnection instead, so you will be able to get data using "await conn.GetAsync(id)" and this way it won't block the main thread.

Create a Blank Database – A database reference can be created by passing the file path the SQLiteConnection class constructor. You do not need to check if the file already exists – it will automatically be created if required, otherwise the existing database file will be opened.
var db = new SQLiteConnection (dbPath);
Save Data – Once you have created a SQLiteConnection object, database commands are executed by calling its methods, such as CreateTable and Insert like this:
db.CreateTable<Stock> ();
db.Insert (newStock); // after creating the newStock object
Retrieve Data – To retrieve an object (or a list of objects) use the following syntax:
var stock = db.Get<Stock>(5); // primary key id of 5
var stockList = db.Table<Stock>();
For more info use following link:
https://developer.xamarin.com/guides/android/application_fundamentals/data/part_3_using_sqlite_orm/#Using_SQLite.NET

You need to check in your DB file if the table really exists.
Extract the database from your Android device/simulator with ADB
Example: adb pull //.db .
It will download the DB file to your computer.
Then, use a tool such as "DB Browser for SQLite" (http://sqlitebrowser.org/) to open your DB file and check if your table exists.
Other common mistakes when using SQLite with Android are:
the file is not found (the path in your connectionstring is not good)
the name is not the one your think (maybe in your case, it is "Record" and not "Records")
Hope it will help.

SQL Change Tracking and Microsoft Sync Framework

I'm kind of new with databases and SQL and I'm struggling trying to understand how SQL Change Tracking and Microsoft Sync Framework work together.
I couldn't find some clear examples about how to sync databases with Microsoft Sync Framework but hopefully I found this site, modified the code and got syncing working on my two databases, here is the code I got:
// Server connection
using (SqlConnection serverConn = new SqlConnection(serverConnectionString))
{
if (serverConn.State == ConnectionState.Closed)
serverConn.Open();
// Client connection
using (SqlConnection clientConn = new SqlConnection(clientConnectionString))
{
if (clientConn.State == ConnectionState.Closed)
clientConn.Open();
const string scopeName = "DifferentPKScope";
// Provision Server
var serverProvision = new SqlSyncScopeProvisioning(serverConn);
if (!serverProvision.ScopeExists(scopeName))
{
var serverScopeDesc = new DbSyncScopeDescription(scopeName);
var serverTableDesc = SqlSyncDescriptionBuilder.GetDescriptionForTable(table, serverConn);
// Add the table to the descriptor
serverScopeDesc.Tables.Add(serverTableDesc);
serverProvision.PopulateFromScopeDescription(serverScopeDesc);
serverProvision.Apply();
}
// Provision Client
var clientProvision = new SqlSyncScopeProvisioning(clientConn);
if (!clientProvision.ScopeExists(scopeName))
{
var clientScopeDesc = new DbSyncScopeDescription(scopeName);
var clientTableDesc = SqlSyncDescriptionBuilder.GetDescriptionForTable(table, clientConn);
// Add the table to the descriptor
clientScopeDesc.Tables.Add(clientTableDesc);
clientProvision.PopulateFromScopeDescription(clientScopeDesc);
clientProvision.SetCreateTrackingTableDefault(DbSyncCreationOption.CreateOrUseExisting);
clientProvision.Apply();
}
// Create the sync orchestrator
var syncOrchestrator = new SyncOrchestrator();
// Setup providers
var localProvider = new SqlSyncProvider(scopeName, clientConn);
var remoteProvider = new SqlSyncProvider(scopeName, serverConn);
syncOrchestrator.LocalProvider = localProvider;
syncOrchestrator.RemoteProvider = remoteProvider;
// Set the direction of sync session
syncOrchestrator.Direction = direction;
// Execute the synchronization process
return syncOrchestrator.Synchronize();
}
}
So on this way any changes are synchronized between my two databases. But I wanted a way for my C# app to automatically synchronize both databases when something changes so I found something called Change Tracking here. I downloaded the example code that provides a SynchronizationHelper that also creates tables in my databases called "{TableName}_tracking". This is another table that tracks the changes and indeed it does, whenever I change something in my database the _tracking is updated with the elements I changed, added or removed. Change Tracking doesn't automatically synchronize my databases, it just keeps track of the changes in them, what's the purpose of this?
With the first code, synchronization works but no _tracking table is created, does it just synchronize everything in the table no matter what changed? If that's the case, for big databases I should be using Change Tracking?
Maybe this is something trivial but I have been googling and testing a lot of code but I can't find a clear answer.

When you install Sync Framework, it comes with a help file that includes several walkthroughs of synchronizing databases. the first link you referred to and the second uses the same sync provider and they both have tracking tables. Sync Framework supports using the built-in SQL Change Tracking feature or using a custom-one that Sync Framework creates by itself (the _tracking).
Sync Framework sits outside of your database and you need to invoke it in order to fire the synchronization. Change Tracking is what it says it is- tracking changes.
if you want your databases to do the sync, you might want to check SQL Replication instead.

Script Uncommitted data from table using SMO

I have a C# win form application which has a facility to backup databases with data to a script file while the application running.
I used following code to script the database using SMO;
public StringCollection GenerateDatabaseScript(string databaseName)
{
//Validate database name goes here
StringCollection dbScript = new StringCollection();
//Create db connection
sqlDataAccess.DBConnect(databaseName); //Custom class to do SQL data operations (sqlDataAccess)
//Create server and database objects
var serverConn = new ServerConnection(sqlDataAccess.Connection);
var dbServer = new Server(serverConn);
var database = dbServer.Databases[databaseName];
//Set script database options here
//--
//Set script database tables option here
//--
//Script database creation
//I also use a method 'ScriptObjectWithBatchDelimiter' to add GO delimiter for each command manually.
dbScript.AddRange(ScriptObjectWithBatchDelimiter(database.Script(dbScriptingOptions)).ToArray());
//Set focus to new db
dbScript.Add(string.Format("USE [{0}]", databaseName));
dbScript.Add("GO");
foreach (Table table in database.Tables)
{
//Skip scripting system tables
if (table.IsSystemObject)
continue;
//Script table
dbScript.AddRange(ScriptObjectWithBatchDelimiter(table.EnumScript(tableScriptingOptions)).ToArray());
}
return dbScript;
}
Problem occurs in this line when encountering a table in the database data is not committed ROWLOCK;
table.EnumScript(tableScriptingOptions)
The problem is how can I script data with READUNCOMMITTED? Is there any properties that I can set to achieve this?
The same question is asked here, but the only answer provided not suitable.
UPDATE: Following code is tried (assumed with the Isolation part in the name) but, still not working.
database.SetSnapshotIsolation(true);

I think what you are looking for is this:
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
msdn: "Specifies that statements can read rows that have been modified by other transactions but not yet committed."
so wrap your scripting work inside a transaction with Isolation Level "ReadUncommited".
this is a good example how to use transactions in c#:
https://msdn.microsoft.com/en-us/library/5ha4240h(v=vs.110).aspx

Dynamics Crm: creating Connection entities via API

So Connections in Dynamics CRM provide a general purpose way of linking things together.
Internally the Connections entity has a Record1Id attribute and a Record2Id attribute, among other things.
When you create a connection via the UI, CRM actually "creates two entries in the Connection table in the database. Each entry allows you to search for the related record from the originating record or the related record."
That is, if you connect A and B, it saves two rows to the (behind the scenes) table:
one with Record1Id = A and Record2Id = B
and one with Record1Id = B and Record2Id = A
This is to make searching for connections easier. If you do an Advanced Find on connections, you only have to do the search 'one way round'.
So my question is:
When you create Connections via the API (late bound), which goes something like this:
Entity connection = new Entity("connection");
connection["record1id"] = new EntityReference("contact", someContactId);
connection["record1objecttypecode"] = new OptionSetValue(2);
connection["record1roleid"] = new EntityReference("connectionrole", someConnectionRoleId);
connection["record2id"] = new EntityReference("incident", someCaseId);
connection["record2objecttypecode"] = new OptionSetValue(122);
connection["record2roleid"] = new EntityReference("connectionrole", someOtherConnectionRoleId);
var newId = service.Create(connection);
... is it sufficient to create them 'one way round' as above, and then behind the scenes CRM will create connections in both directions?
... or do you need to manually create them in both directions? (by saving twice and swapping round the record1id record2id values, etc)
Or, in other words, does the CRM API for Connections encapsulate the 'its actually two connections behind the scenes' functionality, or do you need to manually handle that yourself?

You just need to create one connection record. One thing to note is I don't think you need to set the typecodes as you are doing above. Just setting the logical names in the entity references should be enough. Here is the sample from the SDK:
Connection newConnection = new Connection
{
Record1Id = new EntityReference(Account.EntityLogicalName,
_accountId),
Record1RoleId = new EntityReference(ConnectionRole.EntityLogicalName,
_connectionRoleId),
Record2RoleId = new EntityReference(ConnectionRole.EntityLogicalName,
_connectionRoleId),
Record2Id = new EntityReference(Contact.EntityLogicalName,
_contactId)
};
_connectionId = _serviceProxy.Create(newConnection);