AN INTRODUCTION TO INTERCEPTION IN EF CORE

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AN INTRODUCTION TO INTERCEPTION IN EF CORE
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AN INTRODUCTION TO INTERCEPTION IN EF CORE

• Entity Framework or EF Core is a lightweight,
  could be extended, and a cross-platform version
  of the commonly known Entity Framework data
  access technology.
• EF Core is an object-relational mapper (O/RM)
  that allows .NET developers to work with a
  database that uses .NET objects. It removes the
  need for much of the data-access code which
  developers usually require to write codes. EF
  Core supports several database engines.
• Presently, Entity Framework Core yet does not
  have all of the attributes provided by pre-Core
  versions. One of the features is an ability to
  intercept questions, something which was offered
  by the IDbCommandInterceptor, IDbCommandTreeInterc
  eptor interfaces.

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AN INTRODUCTION TO INTERCEPTION IN EF CORE

• Entity Framework or EF Core is a lightweight,
  could be extended, and a cross-platform version
  of the commonly known Entity Framework data
  access technology.
• EF Core is an object-relational mapper (O/RM)
  that allows .NET developers to work with a
  database that uses .NET objects. It removes the
  need for much of the data-access code which
  developers usually require to write codes. EF
  Core supports several database engines.
• Presently, Entity Framework Core yet does not
  have all of the attributes provided by pre-Core
  versions. One of the features is an ability to
  intercept questions, something which was offered
  by the IDbCommandInterceptor, IDbCommandTreeInterc
  eptor interfaces.

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• The EF Core 2.0 has an interception at the SQL
  level, and you can only get to this in a rather
  complicated way, via the DiagnosticSource
  mechanism. Here we shall discuss on how to create
  a class with two methods, as shown below
• Public class CommandListener
• DiagnosticName(Microsoft.EntityFrameworkCore.Dat
  abase.Command.CommandExecuting)
• public void OnCommandExecuting(DbCommand command,
  DbCommandMethod executeMethod, Guid commandId,
  Guid connectionId, bool async, DateTimeOffset
  startTime)
• DiagnosticName (Microsoft.EntityFrameworkCore.Da
  tabase.Command.CommandExecuted)
• public void OnCommandExecuted(object result, bool
  async)
• You will require the Microsoft.Extensions.Diagnost
  icAdapter NuGet package to assemble this.

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• The methods can be hooked to EF Core as shown
  below
• var listener ctx.GetServiceltDiagnosticSourcegt()
  
• (listener as DiagnosticListener).SubscribeW
  ithAdapter(new CommandListener())
• Here, ctx is a DbContext, and it is being tried
  to access its registered DiagnosticSource
  service, which is a DiagnosticListener. You need
  to add a subscriber, and thats it!
• From the OnCommandExecuted method you can summon
  these methods whatever you choose, as long you
  keep the DiagnosticName features, the result
  parameter would contain either a scalar, a number
  or a RelationalDataReader object a sync, and
  would tell you exactly what version of the method
  was implemented.
• OnCommandExecuting is quite amazing because there
  you can get an access to the DbCommand which is
  on how to implement the SQL command and can edit
  its SQL or parameters.
• There are other mechanisms of interception as
  well, like the IQuerySqlGenerator and
  IQueryCompiler, to be covered later.
• With this, we conclude. Keep coding!

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