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MongoDB Change Stream

I try to code a MongoDB change stream. But if I do some changes, my code doesn't detect the changes. If the code detects the changes I have to get the operation type - according to my understanding. Moreover, how can I insert the changes in the other database? Is it so "easy", that I code a new database connection and update/insert/delete the collection/database?
What did I Code?
`
lang-cs
string mongo_db_client = "mongodb://localhost:27017";
string m_database = "myDataBase";
string m_collection ="myCollection";
MongoClient dbClient = new MongoClient(mongo_db_client);
var database = dbClient.GetDatabase(m_database);
var collection = database.GetCollection<BsonDocument>(m_collection);
var cursor = collection.Watch();
var the_operation_type = null;
if(cursor != null)
{
using(cursor)
{
var curr = cursor.Current;
if (curr != null)
{
foreach (var change in curr)
{
try
{
the_operation_type= change.OperationType;
}
catch(NullReferenceException e)
{
Log(e.ToString());
}
}
}
}
}
`

Force users to update to latest version

I have an app published in the Play and App store, now I am in the work of publishing a new version for the app to both Play (Android) and App stores (iOS). Now, I want all the users to update to the new version when they use the app and not allow them to continue using the older version of the app without updating to the newer version.
Can anyone suggest me on how to force the users to update the app to the latest version once it is released in Play and App stores?

I don't know whether it is professional way or not., but this is the idea which struck my mind.
Add a variable with that app's version in App.cs or Mainpage.cs and and API with the current version as response.
Now check with the app's version and current version and redirect to homepage / any other page.
var version = 1.0;
var currentversion = 2.0; /* from API */
if(version == currentversion)
{
Navigation.PushModalAsync(new HomePage());
}
else
{
Navigation.PushModalAsync(new UpdatePage());
}

We must stop the old versions in the Play and App store.
For the future to do not stop (if we have some host - we should have it :) ):
someway save the version in the server side
every time when needed check the current version: getPackageManager().getPackageInfo(getPackageName(), 0).versionCode with version from server and force to update if needed.
good luck

How I am doing it my app is, when app starting in MyActivity I have code below
private void CompareVersion()
{
double currentVersion = 0d;
double appStoreversion =Convert.ToDouble(CosntValues.PlayStoreValues);
bool IsUpdateRequired = false;
if (Context.PackageName != null)
{
PackageInfo info = Context.PackageManager.GetPackageInfo(Context.PackageName, PackageInfoFlags.Activities);
string currentVersionStrig = info.VersionName;
currentVersion = Convert.ToDouble(currentVersionStrig);
}
try
{
if (IsUpdateRequired == false)
{
if (CheckNetConnection.IsNetConnected())
{
using (var webClient = new System.Net.WebClient())
{
var task = new VersionChecker();
task.Execute();
if ((appStoreversion.ToString() != currentVersion.ToString() && (appStoreversion > currentVersion)))
{
IsUpdateRequired = true;
}
}
}
}
if (IsUpdateRequired)
{
Activity.RunOnUiThread(() =>
{
AlertDialog dialog = null;
var Alertdialog = new Android.App.AlertDialog.Builder(Context);
Alertdialog.SetTitle("Update Available");
Alertdialog.SetMessage($"A new version of [" + appStoreversion + "] is available. Please update to version [" + appStoreversion + "] now.");
Alertdialog.SetNegativeButton("Cancel", (sender, e) =>
{
if (dialog == null)
{
dialog = Alertdialog.Create();
}
dialog.Dismiss();
});
Alertdialog.SetPositiveButton("Update", async (sender, e) =>
{
string appPackage = string.Empty;
try
{
appPackage = Application.Context.PackageName;
await Utilities.Logout(this.Activity);
var ints = new Intent(Intent.ActionView, Android.Net.Uri.Parse("market://details?id=" + appPackage));
ints.SetFlags(ActivityFlags.ClearTop);
ints.SetFlags(ActivityFlags.NoAnimation);
ints.SetFlags(ActivityFlags.NewTask);
Application.Context.StartActivity(ints);
//StartActivity(new Intent(Intent.ActionView, Android.Net.Uri.Parse("market://details?id=" + "com.sisapp.in.sisapp")));
}
catch (ActivityNotFoundException)
{
var apppack = Application.Context.PackageName;
//Default to the the actual web page in case google play store app is not installed
//StartActivity(new Intent(Intent.ActionView, Android.Net.Uri.Parse("https://play.google.com/store/apps/details?id=" + "com.app.in.app")));
await Utilities.Logout(this.Activity);
var ints = new Intent(Intent.ActionView, Android.Net.Uri.Parse("market://details?id=" + appPackage));
ints.SetFlags(ActivityFlags.ClearTop);
ints.SetFlags(ActivityFlags.NoAnimation);
ints.SetFlags(ActivityFlags.NewTask);
Application.Context.StartActivity(ints);
}
//this kills the app
Android.OS.Process.KillProcess(Android.OS.Process.MyPid());
System.Environment.Exit(1);
});
if (dialog == null)
dialog = Alertdialog.Create();
dialog.Show();
});
}
}
catch (Exception ex)
{
var objLog = new LogService();
objLog.MobileLog(ex, SISConst.UserName);
}
}
Followed by two separate above used classes
public class VersionChecker : AsyncTask
{
protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] #params)
{
var val1 = Jsoup.Connect("https://play.google.com/store/apps/details?id=" + "com.app.in.app" + "&hl=en")
.Timeout(30000).UserAgent("Mozilla/5.0 (Windows; U; WindowsNT 5.1; en-US; rv1.8.1.6) Gecko/20070725 Firefox/2.0.0.6").Referrer("http://www.google.com")
.Get();
var val2 = val1.Select(".htlgb");
var val3 = val2.Get(7).ToString();
//here mobile app version is of 3 values like 2.1, 4.2 etc
var version = val3.Substring(val3.IndexOf(">") + 1, 3); //fetching only 3 values ex 1.1
CosntValues.PlayStoreValues = version;
return version;
}
}
public static class CosntValues
{
public static string PlayStoreValues { get; set; }
}
Disclaimer: Use your app package name & above code is statically supporting for 3 digit version like 1.1, 1.2 etc.
Hope it help you

With this plugin I found a good solution and works perfectly in production. I strongly recommend this plugin. With this solution you can even give the user the possibility to go to the store right from your app
For example:
var isLatest = await CrossLatestVersion.Current.IsUsingLatestVersion();
if (!isLatest) //If the user does not have the last version
{
var update = await DisplayAlert("New version available", "There is a new version of our app. Would you like to download it?", "Yes", "No");
if (update)
{
//Open the store
await CrossLatestVersion.Current.OpenAppInStore();
}
}

The underlying provider failed on Open / The operation is not valid for the state of the transaction

Here is my code
public static string UpdateEmptyCaseRevierSet() {
string response = string.Empty;
using (System.Transactions.TransactionScope tran = new System.Transactions.TransactionScope()) {
using (var db = new Entities.WaveEntities()) {
var maxCaseReviewersSetID = db.CaseReviewerSets.Select(crs => crs.CaseReviewersSetId).Max();
var emptyCHList = db.CaseHistories.Where(ch => ch.CaseReviewersSetID == null && ch.IsLatest == true && ch.StatusID != 100).ToList();
for(int i=0; i < emptyCHList.Count; i++) {
var emptyCH = emptyCHList[i];
var newCaseReviewerSET = new Entities.CaseReviewerSet();
newCaseReviewerSET.CreationCHID = emptyCH.CHID;
db.CaseReviewerSets.Add(newCaseReviewerSET);
emptyCH.CaseReviewerSet = newCaseReviewerSET;
}
db.SaveChanges();
}
tran.Complete();
}
return response;
}
The exception occures on "db.SaveChanges()"
I saw in another post with the same error message something about "it seems I cannot have two connections opened to the same database with the TransactionScope block." but I dont think that this has anything to do with my case.
Additionally the number of records to insert and update in total are 2700, witch is not that many really. But it does take quite a lot of time to complete the for statement (10 minutes or so). Since everything happening within the for statement is actually happening in the memory can someone please explane why is this taking so long ?

You can try as shown below using latest db.Database.BeginTransaction API.
Note : use foreach instead of for
using (var db = new Entities.WaveEntities())
{
using (var dbContextTransaction = db.Database.BeginTransaction())
{
try
{
var maxCaseReviewersSetID = db.CaseReviewerSets.Select(crs => crs.CaseReviewersSetId).Max();
var emptyCHList = db.CaseHistories.Where(ch => ch.CaseReviewersSetID == null && ch.IsLatest == true && ch.StatusID != 100).ToList();
foreach(var ch in emptyCHList) {
var newCaseReviewerSET = new Entities.CaseReviewerSet();
newCaseReviewerSET.CreationCHID = ch.CHID;
db.CaseReviewerSets.Add(newCaseReviewerSET);
}
db.SaveChanges();
dbContextTransaction.Commit();
}
catch (Exception)
{
dbContextTransaction.Rollback();
}
}
}

C# Stops Executing When Opening A Connection To MySql

I am writing an application to transfer data from a simulated OPC server to a MySql Database. I am using some of the libraries from OPC Foundation - OPCNETAPI.DLL, OPCNETAPI.COM.DLL.
I have the program reading from the server happily, but it seems as soon as I open a connection inside the loop of reading data, it loops about 5 times and then stops executing.. There are no exceptions thrown and I have tried for hours to work it out and miserably failed.
I've also changed VisualStudio to break when an exception is thrown, and it doesn't
Hopefully some one may know whats going on, but there is nothing obvious, hopefully the following code will spark ideas!
Windows Forms Code
public void readplc()
{
Opc.URL url = new Opc.URL("opcda://localhost/Matrikon.OPC.Simulation.1");
Opc.Da.Server server = null;
OpcCom.Factory fact = new OpcCom.Factory();
server = new Opc.Da.Server(fact, null);
try
{
server.Connect(url, new Opc.ConnectData(new System.Net.NetworkCredential()));
}
catch (Exception ecy)
{
}
// Create a group
Opc.Da.Subscription group;
Opc.Da.SubscriptionState groupState = new Opc.Da.SubscriptionState();
groupState.Name = "Group";
groupState.Active = true;
group = (Opc.Da.Subscription)server.CreateSubscription(groupState);
// add items to the group.
Opc.Da.Item[] items = new Opc.Da.Item[2];
items[0] = new Opc.Da.Item();
items[0].ItemName = "Random.Int1";
items[1] = new Opc.Da.Item();
items[1].ItemName = "Random.Time";
items = group.AddItems(items);
group.DataChanged += new Opc.Da.DataChangedEventHandler(OnTransactionCompleted);
}
public void OnTransactionCompleted(object group, object hReq, Opc.Da.ItemValueResult[] items)
{
for (int i = 0; i < items.GetLength(0); i++)
{
try
{
string a = items[i].Value.ToString();
string b = items[i].ItemName;
string c = items[i].Key;
MySqlConnection conn = new MySqlConnection("server=localhost;user id=localhost;password=localhost;database=localhost;pooling=false");
conn.Open();
conn.Close();
}
catch (Exception ec)
{
MessageBox.Show(ec.Message);
}
}
}
I have set break points throughout the code, stepped through everything possible and still nothing obvious that's causing the issue.

Why doesn't SMO scripter generate foreign key headers?

I'm creating a program to generate my database schema using the SMO libraries distributed with SQL Server 2008.
I've gotten the scripter outputting code which is virtually the same as SQL Server Management Studio outputs when it's configured to output everything, but with one curious exception: it doesn't output comment headers for the foreign key constraints it generates at the bottom, whereas SSMS does. Can anyone figure out why this is? Here's my code:
private void btnExportScript_Click(object sender, EventArgs ea) {
Server srv = setupConnection();
// Reference the database
if (!srv.Databases.Contains(cbChooseDb.SelectedItem.ToString())) {
_utils.ShowError("Couldn't find DB '" + cbChooseDb.SelectedItem.ToString() + "'.");
return;
}
Database db = srv.Databases[cbChooseDb.SelectedItem.ToString()];
StringBuilder builder = new StringBuilder();
try {
Scripter scrp = new Scripter(srv);
scrp.Options.AppendToFile = false;
scrp.Options.ToFileOnly = false;
scrp.Options.ScriptDrops = false; // Don't script DROPs
scrp.Options.Indexes = true; // Include indexes
scrp.Options.DriAllConstraints = true; // Include referential constraints in the script
scrp.Options.Triggers = true; // Include triggers
scrp.Options.FullTextIndexes = true; // Include full text indexes
scrp.Options.NonClusteredIndexes = true; // Include non-clustered indexes
scrp.Options.NoCollation = false; // Include collation
scrp.Options.Bindings = true; // Include bindings
scrp.Options.SchemaQualify = true; // Include schema qualification, eg. [dbo]
scrp.Options.IncludeDatabaseContext = false;
scrp.Options.AnsiPadding = true;
scrp.Options.FullTextStopLists = true;
scrp.Options.IncludeIfNotExists = false;
scrp.Options.ScriptBatchTerminator = true;
scrp.Options.ExtendedProperties = true;
scrp.Options.ClusteredIndexes = true;
scrp.Options.FullTextCatalogs = true;
scrp.Options.SchemaQualifyForeignKeysReferences = true;
scrp.Options.XmlIndexes = true;
scrp.Options.IncludeHeaders = true;
// Prefectching may speed things up
scrp.PrefetchObjects = true;
var urns = new List<Urn>();
// Iterate through the tables in database and script each one.
foreach (Table tb in db.Tables) {
if (tb.IsSystemObject == false) {
// Table is not a system object, so add it.
urns.Add(tb.Urn);
}
}
// Iterate through the views in database and script each one. Display the script.
foreach (Microsoft.SqlServer.Management.Smo.View view in db.Views) {
if (view.IsSystemObject == false) {
// View is not a system object, so add it.
urns.Add(view.Urn);
}
}
// Iterate through the stored procedures in database and script each one. Display the script.
foreach (StoredProcedure sp in db.StoredProcedures) {
if (sp.IsSystemObject == false) {
// Procedure is not a system object, so add it.
urns.Add(sp.Urn);
}
}
// Start by manually adding DB context
builder.AppendLine("USE [" + db.Name + "]");
builder.AppendLine("GO");
System.Collections.Specialized.StringCollection sc = scrp.Script(urns.ToArray());
foreach (string st in sc) {
// It seems each string is a sensible batch, and putting GO after it makes it work in tools like SSMS.
// Wrapping each string in an 'exec' statement would work better if using SqlCommand to run the script.
builder.Append(st.Trim(new char[] { '\r', '\n' }) + "\r\nGO\r\n");
}
}
catch (Exception ex) {
showExceptionError("Couldn't generate script.", ex);
return;
}
try {
File.WriteAllText(txtExportToFile.Text, builder.ToString());
_utils.ShowInfo("DB exported to script at: " + txtExportToFile.Text);
}
catch (Exception ex) {
showExceptionError("Couldn't save script file.", ex);
return;
}
}
Note that foreign keys fall under the category of DRI constraints, and are scripted because of scrp.Options.DriAllConstraints = true;.

I have a solution here: Can't get EnumScript() to generate constraints
for some reason, Scripter won't emit DRI constraints (foreign keys, etc) when it's given a list of Urns, but it will if it's given one Urn at a time. The trick there is to give the Urns in the order of their ancestry: tables have to be defined before they're referenced by constraints. To do that I've used the DependencyWalker.
Here's a synopsis:
var urns = new List<Urn>();
Scripter schemaScripter = new Scripter(srv) { Options = schemaOptions };
Scripter insertScripter = new Scripter(srv) { Options = insertOptions };
var dw = new DependencyWalker(srv);
foreach (Table t in db.Tables)
if (t.IsSystemObject == false)
urns.Add(t.Urn);
DependencyTree dTree = dw.DiscoverDependencies(urns.ToArray(), true);
DependencyCollection dColl = dw.WalkDependencies(dTree);
foreach (var d in dColl)
{
foreach (var s in schemaScripter.Script(new Urn[] { d.Urn }))
strings.Add(s);
strings.Add("GO");
if (scriptData)
{
int n = 0;
foreach (var i in insertScripter.EnumScript(new Urn[] {d.Urn}))
{
strings.Add(i);
if ((++n) % 100 == 0)
strings.Add("GO");
}
}
}
Note: adding a "GO" every so often keeps the batch size small so SSMS doesn't run out of memory.