EF Best practices

Fast insert

1.    _unitOfWorkRoute.Context.ChangeTracker.AutoDetectChangesEnabled = false;
2. ef bulk insert.
3. Install-Package Z.EntityFramework.Extensions

Like
            _unitOfWorkVehicle.AmenityRepository.Table.Where(p => EF.Functions.Like(p.Name, "%arm%"));


Fast Update / Delete

1. Bulk update
2. update without select

   using (var context = new StudentDbContext())

            {

                var student = new Student()

                {

                    Id = 2,

                    Name = "Kasun"

                };

                context.Attach(student);

                context.Entry(student).State = EntityState.Modified;

                context.SaveChanges();

                Console.WriteLine("saved");

            }

  var student = new Student()

                {

                    Id = 2,

                    Name = "Kasun"

                };

                context.Attach(student);

                context.Entry(student).Property(p => p.Name).IsModified = true;

                context.SaveChanges();

Threads

Process
======
OS facilitates the execution of the program by providing the resources required. each process has a unique process ID

Threads
======
Inside Process, there might be one(main thread) to many lightweight processes has. Those are called threads

Advantages of thread

1. to maintain a responsive user interface.
2. to split large ask to small task and give deferent cpu to complete them.

Disadvantages

1. need to consider thread safe,context switch.

Example 1

Without threads

for print success (on main thread) this will wait for complete TimeConsumingWork

With Threads

Main Thread will not pouse for complete time-consuming task. because it is on another thread

Thread Start Delegate

To start a thread, for Thread class we need to pass not a function but function pointer. delegate is the function pointer. when execute var t = new Thread(TimeConsumingWork); behind the seen program creates function pointer to TimeConsumingWork and pass to the Thread Class implicitly. but for more understand we can use ThreadStart delegate in deferent ways.

1.  var threadStartDelegate = new ThreadStart(TimeConsumingWork);
    var thread = new Thread(threadStartDelegate);
2.  var t = new Thread(() => TimeConsumingWork());
3.   var t = new Thread(delegate () { TimeConsumingWork(); });

ParameterizedThreadStart delegate
   
  If need to pass some parameters to the method we can use parameterizedThreadStart delegate

Retrieving data from thread function

Thread Chaining

Task.Run(async () =>
{
    await LongTaskAsync("A");
    await LongTaskAsync("B");
    await LongTaskAsync("C");
});

Thread.Join.

Block the current thread and wait untile all join threads are complete.Thread.Join has overrload method that specify the timeout.

without join

with join

with Join(timeout);

if timeout exceeded, main thread continue. but after particular thread will finish there work

===============================================================

Comparison

Without Concurrency or parallelism 

With Async await 1

With Async Await 2

Using Threads/parallelism 

EFCore-SQL mapper

INCLUDE

Select all student Info,subjectIds , what studentId = 2

var lst = context.Student.Where(p => p.Id == 2)

         .Include(p => p.StudentSubjects) 

          .ToList();

01) first execute the query to read particular student

SELECT [p].[Id], [p].[Birthday], [p].[Name]
FROM [Student] AS [p]
WHERE [p].[Id] = 2
ORDER BY [p].[Id]

02) Second, execute the query for read studentSubject

SELECT [p.StudentSubjects].[StudentId], [p.StudentSubjects].[SubjectId], [p.StudentSubjects].[AdmissionFrom]
FROM [StudentSubject] AS [p.StudentSubjects]
INNER JOIN (
    SELECT [p0].[Id]
    FROM [Student] AS [p0]
    WHERE [p0].[Id] = 2
) AS [t] ON [p.StudentSubjects].[StudentId] = [t].[Id]
ORDER BY [t].[Id]

two separate SQL will generate and execute for two tables.

====================================================
Select all Student info,subjectIds and phone number what student id == 2

      var lst = context.Student.Where(p => p.Id == 2)
                    .Include(p => p.StudentSubjects)
                    .Include(p=>p.PhoneNumbers)
                    .ToList();
01) first execute the query to read particular student

SELECT [p].[Id], [p].[Birthday], [p].[Name]
FROM [Student] AS [p]
WHERE [p].[Id] = 2
ORDER BY [p].[Id]

02) Second, execute the query for read studentSubject

SELECT [p.StudentSubjects].[StudentId], [p.StudentSubjects].[SubjectId], [p.StudentSubjects].[AdmissionFrom]
FROM [StudentSubject] AS [p.StudentSubjects]
INNER JOIN (
    SELECT [p0].[Id]
    FROM [Student] AS [p0]
    WHERE [p0].[Id] = 2
) AS [t] ON [p.StudentSubjects].[StudentId] = [t].[Id]
ORDER BY [t].[Id]

02) Second, execute the query for reading Student phone numbers

SELECT [p.PhoneNumbers].[StudentId], [p.PhoneNumbers].[PhoneNumber]
FROM [PhoneNumbers] AS [p.PhoneNumbers]
INNER JOIN (
    SELECT [p1].[Id]
    FROM [Student] AS [p1]
    WHERE [p1].[Id] = 2
) AS [t0] ON [p.PhoneNumbers].[StudentId] = [t0].[Id]
ORDER BY [t0].[Id]

three separate SQL will generate and execute for 3 tables

===========================================

03) ThenInclude

 Select Student info and Subject what student id 2 has

 var lst = context.Student.Where(p => p.Id == 2)
                    .Include(p => p.StudentSubjects)
                    .ThenInclude(p=>p.Subject)
                    .ToList();

01) first execute the query to read particular student

SELECT [p].[Id], [p].[Birthday], [p].[Name]
FROM [Student] AS [p]
WHERE [p].[Id] = 2
ORDER BY [p].[Id]

02) Second, execute the query for read studentSubject and subjects

SELECT [p.StudentSubjects].[StudentId], [p.StudentSubjects].[SubjectId], [p.StudentSubjects].[AdmissionFrom], [s.Subject].[Id], [s.Subject].[Name]
FROM [StudentSubject] AS [p.StudentSubjects]
INNER JOIN [Subject] AS [s.Subject] ON [p.StudentSubjects].[SubjectId] = [s.Subject].[Id]
INNER JOIN (
    SELECT [p0].[Id]
    FROM [Student] AS [p0]
    WHERE [p0].[Id] = 2
) AS [t] ON [p.StudentSubjects].[StudentId] = [t].[Id]

ORDER BY [t].[Id]

(ThenInclude query makes inner join query)

====================================

Select all subject teaches what student id==2

var lst = context.Student.Where(p => p.Id == 2)
                    .Include(p => p.StudentSubjects)
                    .ThenInclude(p=>p.Subject.Teachers)
                    .ToList();
01) select student who has id 2 

SELECT [p].[Id], [p].[Birthday], [p].[Name]
FROM [Student] AS [p]
WHERE [p].[Id] = 2
ORDER BY [p].[Id]

02) select studentsubject inner join subject 

SELECT [p.StudentSubjects].[StudentId], [p.StudentSubjects].[SubjectId], [p.StudentSubjects].[AdmissionFrom], [s.Subject].[Id], [s.Subject].[Name]
FROM [StudentSubject] AS [p.StudentSubjects]
INNER JOIN [Subject] AS [s.Subject] ON [p.StudentSubjects].[SubjectId] = [s.Subject].[Id]
INNER JOIN (
    SELECT [p0].[Id]
    FROM [Student] AS [p0]
    WHERE [p0].[Id] = 2
) AS [t] ON [p.StudentSubjects].[StudentId] = [t].[Id]

ORDER BY [t].[Id], [s.Subject].[Id]

02) select teaches 

SELECT [p.StudentSubjects].[StudentId], [p.StudentSubjects].[SubjectId], [p.StudentSubjects].[AdmissionFrom], [s.Subject].[Id], [s.Subject].[Name]
FROM [StudentSubject] AS [p.StudentSubjects]
INNER JOIN [Subject] AS [s.Subject] ON [p.StudentSubjects].[SubjectId] = [s.Subject].[Id]
INNER JOIN (
    SELECT [p0].[Id]
    FROM [Student] AS [p0]
    WHERE [p0].[Id] = 2
) AS [t] ON [p.StudentSubjects].[StudentId] = [t].[Id]

ORDER BY [t].[Id], [s.Subject].[Id]


========================================
Select student name and teacher name only

result
SELECT [student].[Name] AS [Name0], [subject].[Name] AS [SubjectName]
FROM [Student] AS [student]
INNER JOIN [StudentSubject] AS [studentSubject] ON [student].[Id] = [studentSubject].[StudentId]
INNER JOIN [Subject] AS [subject] ON [studentSubject].[SubjectId] = [subject].[Id]
WHERE [student].[Id] = 2
===============================================================

Include + Conditions

Select phone numbers start with 033 who has id 2



========================================
multiple include + then include

  var lst = context.Student.Where(p => p.Id == 2)
                    .Include(p => p.StudentSubjects)
                    .ThenInclude(p => p.Subject)
                    .Include(p => p.StudentSubjects)
                    .ThenInclude(p => p.Teacher).FirstOrDefault();


1st
SELECT TOP(1) [p].[Id], [p].[Birthday], [p].[Name]
FROM [Student] AS [p]
WHERE [p].[Id] = 2
ORDER BY [p].[Id]

2nd 

SELECT [p.StudentSubjects].[StudentId], [p.StudentSubjects].[SubjectId], [p.StudentSubjects].[AdmissionFrom], [p.StudentSubjects].[TeacherId], [s.Teacher].[Id], [s.Teacher].[Name], [s.Teacher].[SubjectId], [s.Subject].[Id], [s.Subject].[Location], [s.Subject].[Name]
FROM [StudentSubject] AS [p.StudentSubjects]
INNER JOIN [Teachers] AS [s.Teacher] ON [p.StudentSubjects].[TeacherId] = [s.Teacher].[Id]
INNER JOIN [Subject] AS [s.Subject] ON [p.StudentSubjects].[SubjectId] = [s.Subject].[Id]
INNER JOIN (
    SELECT TOP(1) [p0].[Id]
    FROM [Student] AS [p0]
    WHERE [p0].[Id] = 2
    ORDER BY [p0].[Id]
) AS [t] ON [p.StudentSubjects].[StudentId] = [t].[Id]

ORDER BY [t].[Id]


========================================
update single colomn

using (var c = new StudentDbContext())
                {
                    var student = c.Student.First();
                    student.Name = "Saman";
                    c.SaveChanges();

                } 
Select query
SELECT TOP(1) [s].[Id], [s].[Birthday], [s].[Name]
FROM [Student] AS [s]

Update query
exec sp_executesql N'SET NOCOUNT ON;
UPDATE [Student] SET [Name] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;


',N'@p1 int,@p0 nvarchar(4000)',@p1=2,@p0=N'Saman'

========================================Update with same value (Saman is already there.change only dob)

   using (var c = new StudentDbContext())
  {
   var student = c.Student.First();
    student.Name = "Saman";
    student.Birthday = new DateTime(1900,1,1);
    c.SaveChanges();
  } 
exec sp_executesql N'SET NOCOUNT ON;
UPDATE [Student] SET [Birthday] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;


',N'@p1 int,@p0 datetime2(7)',@p1=2,@p0='1900-01-01 00:00:00'

==================================================================

If nothing to update

using (var c = new StudentDbContext())
                {
                    var student = c.Student.First();
                    student.Name = "Saman";
                    student.Birthday = new DateTime(1900,1,1);
                    c.SaveChanges();

                } 
both database has same name what ef send.
then on update query execute.Then all the update query use tracking colomn data

=====================================

Update aggregate root and some aggregate 

  using (var c = new StudentDbContext())
                {
                    var student = c.Subject.Include(p => p.Teachers).First();
                    student.Name = "Commace";
                    student.Teachers[0].Name = "janson";
                    c.SaveChanges();

                } 


Load first subject
SELECT TOP(1) [p].[Id], [p].[Location], [p].[Name]
FROM [Subject] AS [p]

ORDER BY [p].[Id]

Load all teachers to that subject
SELECT [p.Teachers].[Id], [p.Teachers].[Name], [p.Teachers].[SubjectId]
FROM [Teachers] AS [p.Teachers]
INNER JOIN (
    SELECT TOP(1) [p0].[Id]
    FROM [Subject] AS [p0]
    ORDER BY [p0].[Id]
) AS [t] ON [p.Teachers].[SubjectId] = [t].[Id]

ORDER BY [t].[Id]

update subject
exec sp_executesql N'SET NOCOUNT ON;
UPDATE [Subject] SET [Name] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;
',N'@p1 int,@p0 nvarchar(4000)',@p1=1,@p0=N'Commace'

update teacher
exec sp_executesql N'SET NOCOUNT ON;
UPDATE [Teachers] SET [Name] = @p0
WHERE [Id] = @p1;
SELECT @@ROWCOUNT;

',N'@p1 int,@p0 nvarchar(4000)',@p1=1,@p0=N'janson'

Docker

Simple docker file

FROM mcr.microsoft.com/dotnet/core/runtime:2.1 AS base
WORKDIR /app
EXPOSE 5000
COPY . .
ENTRYPOINT ["dotnet", "BBK.Web.Host.dll"]

1. get .net run time for .net core 2.1
2. on docker container go app folder
3. expose 5000 on docker container.
4. copy local/current folder to docker/app
5. run cmd command 

--------------------------------------------------------------------

Connect localhost services from docker
appsetting.json

Server=host.docker.internal; Port=3306; Database=bbkhf; Uid=root; Pwd=dsfdsdfsdf$;"

--------------------------------------------------------------------

Interview Questions

.net core
      (https://www.talkingdotnet.com/asp-net-core-interview-questions/)

1. What is .net core ?
2. 
   

Azure search

https://www.youtube.com/watch?v=onYmw0-4ekA

Azure notification hub

https://www.youtube.com/watch?v=Qb2lXEI6LXo&index=2&list=PLxzlUIszJ8gf2l-BHEBEifKswmUMLCzCB