[Turn] EF Configuring a DbContext

This article transferred from: Https://docs.microsoft.com/en-us/ef/core/miscellaneous/configuring-dbcontext

Note

This documentation are for EF Core. For ef6.x, see Entity Framework 6. +

This article shows patterns is configuring a DbContext with DbContextOptions . Options is primarily used to select and configure the data store. +

Configuring Dbcontextoptions

DbContextMust has an instance of in DbContextOptions order to execute. This can is configured by overriding OnConfiguring , or supplied externally via a constructor argument. +

If Both is used, was OnConfiguring executed on the supplied options, meaning it's additive and can overwrite options supplied to The constructor argument. +

Constructor argument

Context code with constructor+

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PublicClassBloggingcontext:dbcontext{public  bloggingcontext (dbcontextoptions<bloggingcontext> Options Base ( Optionspublic DbSet< Blog> Blogs {get; set;}          

Tip

The base constructor of DbContext also accepts the non-generic version of DbContextOptions . Using the non-generic version is not a recommended for applications with multiple context types. +

Application code to initialize from constructor argument+

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var optionsBuilder = new DbContextOptionsBuilder<BloggingContext>();optionsBuilder.UseSqlite("Filename=./blog.db");using (var context = new BloggingContext(optionsBuilder.Options)){ // do stuff}

Onconfiguringwarning

OnConfiguringOccurs last and can overwrite options obtained from DI or the constructor. This approach does isn't lend itself to testing (unless you target, the full database). +

Context code with onconfiguring+

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PublicClassBloggingcontext:dbcontext{Public dbset<blog> Blogs {Getset;} protected  override  void  OnConfiguring  (DbContextOpt Ionsbuilder optionsbuilder< Span class= "hljs-string" > "filename=./blog.db"); }} 

Application code to initialize with "onconfiguring"+

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using (var context = new BloggingContext()){ // do stuff}

Using DbContext with Dependency injection

EF supports using with DbContext a dependency injection container. Your DbContext type can be added to the service container by using AddDbContext<TContext> . +

AddDbContextWould add make both your DbContext type, TContext , and to the available for injection from the DbContextOptions<TContext> service container. +

See more reading below for information on dependency injection. +

Adding DbContext to Dependency injection+

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 < Span class= "Hljs-keyword" >public  void  configureservices (iservicecollection services "filename=./blog.db"));      

This is requires adding a constructor argument to your DbContext type that accepts DbContextOptions . +

Context Code+

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PublicClassBloggingcontext:dbcontext{public  bloggingcontext (dbcontextoptions<bloggingcontext> Options Base ( Optionspublic DbSet< Blog> Blogs {get; set;}          

Application code (in ASP. NET Core)+

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public MyController(BloggingContext context)

Application code (using serviceprovider directly, less common)+

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using (var context = serviceProvider.GetService<BloggingContext>()){  // do stuff}var options = serviceProvider.GetService<DbContextOptions<BloggingContext>>();

+

Using IDbContextFactory<TContext>

As an alternative to the options above, your may also provide an implementation of IDbContextFactory<TContext> . EF command line tools and dependency injection can use this factory to the create an instance of your DbContext. This is required in order to enable specific design-time experiences such as migrations. +

Implement this interface to enable Design-time services for the context types that does not has a public default constructor. Design-time services would automatically discover implementations of this interface that is in the same assembly as the de rived context. +

Example:+

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Using Microsoft.entityframeworkcore;Using Microsoft.EntityFrameworkCore.Infrastructure;Namespacemyproject{PublicClassBloggingcontextfactory:idbcontextfactory<bloggingcontext> {public bloggingcontext Create() { var optionsbuilder = New dbcontextoptionsbuilder< Bloggingcontext> (); Optionsbuilder.usesqlite ("filename=./blog.db"); return new Bloggingcontext (optionsbuilder.options);          }}

More Reading

• Read Getting Started on ASP. Information on using the EF with ASP.

• Read Dependency Injection to learn more about using DI.

• Read testing with InMemory for more information.

• Read Understanding EF Services For more details on how EF uses dependency injection internally.

[Turn] EF Configuring a DbContext