- Dbcontext generator data annotations how to#
- Dbcontext generator data annotations update#
- Dbcontext generator data annotations code#
Var optionsBuilder = new DbContextOptionsBuilder() Public BloggingContext CreateDbContext(string args) public class BloggingContextFactory : IDesignTimeDbContextFactory
Dbcontext generator data annotations how to#
You can also tell the tools how to create your DbContext by implementing the interface: If a class implementing this interface is found in either the same project as the derived DbContext or in the application's startup project, the tools bypass the other ways of creating the DbContext and use the design-time factory instead. This can be the default constructor if the DbContext is configured using the OnConfiguring method. Then they try to create an instance using a constructor with no parameters. If the DbContext can't be obtained from the application service provider, the tools look for the derived DbContext type inside the project. This can be easily achieved by having a constructor on the DbContext that takes an instance of DbContextOptions as an argument and using the AddDbContext method.
The DbContext itself and any dependencies in its constructor need to be registered as services in the application's service provider. When you create a new ASP.NET Core application, this hook is included by default. Public ApplicationDbContext(DbContextOptions options) Public class ApplicationDbContext : DbContext Public void Configure(IApplicationBuilder app, IWebHostEnvironment env) Public void ConfigureServices(IServiceCollection services) Public static IHostBuilder CreateHostBuilder(string args) EF Core uses this method at design time to access the DbContext => CreateHostBuilder(args).Build().Run() The tools first try to obtain the service provider by invoking Program.CreateHostBuilder(), calling Build(), then accessing the Services property. NET Core Generic Host, the tools try to obtain the DbContext object from the application's service provider. If your startup project uses the ASP.NET Core Web Host or. There are various ways the tools try to create the DbContext: From application services In most cases, it is desirable that the DbContext thereby created is configured in a similar way to how it would be configured at run time.
Dbcontext generator data annotations update#
Note: EF does not include DatabaseGeneratedOption.Computed columns in INSERT or UPDATE statements.Some of the EF Core Tools commands (for example, the Migrations commands) require a derived DbContext instance to be created at design time in order to gather details about the application's entity types and how they map to a database schema.
Dbcontext generator data annotations code#
The above code set the SQL Server function GETDATE() as a default value SQL which will insert the current date and time on each INSERT command. Protected override void OnModelCreating( ModelBuilder modelBuilder) Here, we will specify date function of SQL Server which will generate current date-time value on INSERT command, as shown below.
However, EF does not guarantee that it will setup the actual mechanism to generate values. This tells EF that values are generated for this column in the database. In the above example, the CreatedDate property is marked with the DatabaseGeneratedOption.Computed option. you must provide the unique CourseId value var maths = new Course() Using ( var context = new SchoolContext()) So, each time you will have to provide the value of the CourseId property before calling the SaveChanges() method. In the above example, EF will create the CourseId column in the database and will not mark it as an IDENTITY column. This will be useful to override the default convention for the id properties.įor example, if you want to provide your own values to id properties instead of database generated values, use the None option, as shown below. The DatabaseGenerated attribute takes one out of the following three DatabaseGeneratedOption enum values:ĭatabaseGeneratedOption.None option specifies that the value of a property will not be generated by the underlying database. So, the underlying database generates a value for this column on each insert command, e.g., SQL Server creates an integer IDENTITY column with identity seed and increment to 1.ĮF 6 and EF Core provide the DatabaseGenerated data annotation attribute to configure how the value of a property will be generated. Next Data Annotations - DatabaseGenerated Attribute in EF 6 & EF CoreĪs you know, EF creates an IDENTITY column in the database for all the id (key) properties of the entity, by default.
0 kommentar(er)
