what is dbcontext in entity framework

An instance of DbContext represents a session with the database which can be used to query and save instances of your entities to a database.DbContext is a combination of the Unit Of Work and Repository patterns.. DbContext in EF Core allows us to perform following tasks: The entity classes are managed by the DBContext API. You can set a different value for the timeout at the DbContext level, but this will apply to all operations undertaken by the DbContext which may not be desirable. EF Core 5.0 adds additional mapping options, where an entity can be mapped to a SQL query (called a "defining query"), or to a table-valued function (TVF): As we know DBContext is an autogenerated code created and customized using Scaffolding commands in Entity Framework tools. See e.g. As we know DBContext is an autogenerated code created and customized using Scaffolding commands in Entity Framework tools. As we know DBContext is an autogenerated code created and customized using Scaffolding commands in Entity Framework tools. DBContext will set the EF context for data access and set the DataSet for our model to access data from data source. Entity types are commonly mapped to tables or views such that EF Core will pull back the contents of the table or view when querying for that type. In short: lifespan should be "short", static context is bad. Lazy Loading means that the contents of these properties will be automatically loaded from the database when you try to access them. Modified 9 years, 3 months ago. using (var dbContext = new Chat_ServerEntities()) { var allRec= dbContext.myEntities; dbContext.myEntities.RemoveRange(allRec); dbContext.SaveChanges(); } 2- For Single record It usually looks like this: The Unit of Work and Repository patterns result in the simplest code, as in the CRUD catalog microservice in eShopOnContainers. Entity Framework 4.3 includes a new Code First Migrations feature that allows you to incrementally evolve the database schema as your model changes over time. We are going to call it as EmployeeDbContext Here we will create the following EF Core 5.0 adds additional mapping options, where an entity can be mapped to a SQL query (called a "defining query"), or to a table-valued function (TVF): Create a Context We define a context that derives from System.Data.Entity.DbContext and exposes a typed DbSet for each class in our model. This will provide you can get the following benefits: 1. Flexible entity mapping. The Entity Framework Core Tools contains command-line interface tools (CLI). The main class that coordinates Entity Framework functionality for a given data model is the database context class. The Entity Framework DbContext class is based on the Unit of Work and Repository patterns and can be used directly from your code, such as from an ASP.NET Core MVC controller. I am using entity framework with LINQ. Code First modeling workflow targets a database that doesnt exist and Code First will create it. This article only applies to EF Core, as EF6.x doesnt have all the features needed to lock down the entity class. Following code was helpful for me; 1- For multiple records. EF 4.1 onwards). Entity mapping is just some simple mappings that will impact Entity Framework's understanding of how the classes are mapped to the databases. Entity Framework is an Object/Relational Mapping (O/RM) framework. Your migration might include a long-running task that exceeds the default command timeout value (30 seconds for SQL Server), resulting in an exception being raised. An Entity Framework anti-pattern commonly seen in the wild is to implement the creation and disposal of DbContext in data access methods (e.g. The short answer is that it IS possible, but not an out-of-the-box feature from the EF Core Team. In your code you specify which entities are included in the data model. For those developers, Entity Framework has a modeling workflow referred to as Code First. It is open-source, lightweight, extensible and a cross-platform version of Entity Framework data access technology. Multiple context classes may belong to a single database or two different databases. A University database can be much more complex as a whole but for demo and learning purpose, we Modified 9 years, 3 months ago. 2. In short: lifespan should be "short", static context is bad. For those developers, Entity Framework has a modeling workflow referred to as Code First. Following code was helpful for me; 1- For multiple records. Installing Entity Framework Core Tools. If you really need to refresh some entity and you are using Code First approach with DbContext class, you can use. The best way to refresh entities in your context is to dispose your context and create a new one. It. Your migration might include a long-running task that exceeds the default command timeout value (30 seconds for SQL Server), resulting in an exception being raised. The Unit of Work and Repository patterns result in the simplest code, as in the CRUD catalog microservice in eShopOnContainers. Entity Framework - Database Setup, In this tutorial, we will be using a simple University database. Entity Framework Core is the new version of Entity Framework after EF 6.x. This enables the Lazy Loading feature of Entity Framework. An EF Core DbContext class. using (var dbContext = new Chat_ServerEntities()) { var allRec= dbContext.myEntities; dbContext.myEntities.RemoveRange(allRec); dbContext.SaveChanges(); } 2- For Single record Most often, you will use the generic version of Add but omit the type parameter because the compiler will infer the type from the argument passed in to the method . It usually looks like this: I've followed Adam's answer here and the Entity Framework now works and the Seed() method also works. In your code you specify which entities are included in the data model. You create this class by deriving from the System.Data.Entity.DbContext class. The best way to refresh entities in your context is to dispose your context and create a new one. It simply delays the loading of the related data, until you ask for it. The Unit of Work and Repository patterns result in the simplest code, as in the CRUD catalog microservice in eShopOnContainers. The default implementation of this method does nothing, but it can be overridden in a derived class such that the model can be further configured before it is locked down. DbContext class is the backbone of this entire concept. Entity Framework Code-First: Migrate a database known only at runtime. Entity Framework Core: DbContext. I've followed Adam's answer here and the Entity Framework now works and the Seed() method also works. It is open-source, lightweight, extensible and a cross-platform version of Entity Framework data access technology. In this tutorial I will teach you how to use the Dependency Injection method in Entity Framework Core. Ask Question Asked 10 years, 5 months ago. Entity types are commonly mapped to tables or views such that EF Core will pull back the contents of the table or view when querying for that type. The context is the main class that coordinates Entity Framework functionality for a given data model. in repository methods in a traditional 3-tier application). It is the default behavior of an Entity Framework, where a child entity is loaded only when it is accessed for the first time. 3. This method is called when the model for a derived context has been initialized, but before the model has been locked down and used to initialize the context. Ask Question Asked 10 years, 5 months ago. Entity Framework 4.3 includes a new Code First Migrations feature that allows you to incrementally evolve the database schema as your model changes over time. Entity Framework 4 - lifespan/scope of context in a winform application. The DbContext class is an integral part of Entity Framework. If you'd like to use an Attribute to add Unique Keys to your Entity Framework Core entity classes, you can do what I've posted here Multiple DbContext was first introduced in Entity Framework 6.0. Entity Framework Code-First: Migrate a database known only at runtime. This class is responsible for. Entity Framework Core is the new version of Entity Framework after EF 6.x. Treat DbContext class as a session with the database. The object of DbContext class through Dependency Injection. Entity Framework Core integrates with the .NET Core logging to log SQL and change tracking information to the various output targets. The OP is asking about whether it is possible to add an Attribute to an Entity class for a Unique Key. OR provide the mapping by overriding DBContext OnModelCreating: class webpages_OAuthMembershipEntities : DbContext { protected override void OnModelCreating( DbModelBuilder modelBuilder ) { var config = These methods are new to the DbContext in Entity Framework Core and have no equivalents in previous version of Entity Framework where the DbContext is available (i.e. For example, when using the Student entity class, the related Enrollments will be loaded the first time the Enrollments navigation property is accessed. In the Add Razor Pages using Entity Framework (CRUD) dialog: In the Model class drop-down, select Student (ContosoUniversity.Models). This will provide you can get the following benefits: 1. Let's install the logging provider's NuGet package. These methods are new to the DbContext in Entity Framework Core and have no equivalents in previous version of Entity Framework where the DbContext is available (i.e. Entity Framework Core. In this tutorial I will teach you how to use the Dependency Injection method in Entity Framework Core. If you'd like to use an Attribute to add Unique Keys to your Entity Framework Core entity classes, you can do what I've posted here You can also customize certain Entity Framework behavior. An Entity Framework anti-pattern commonly seen in the wild is to implement the creation and disposal of DbContext in data access methods (e.g. If you leave the default configuration, and dont explicitly tell Entity Framework in your query that you want something other than lazy loading, then lazy loading is what you will get. Entity Framework Core. in repository methods in a traditional 3-tier application). This will provide you can get the following benefits: 1. Select Razor Pages using Entity Framework (CRUD) > ADD. I'm using Ninject to generate and inject the connection string on the DbContext object. Entity Framework Core is a lightweight, extensible, open-sourced version of the Entity Framework Data Access Technology built for .NET Core Applications. Viewed 4k times 5 New! It is the default behavior of an Entity Framework, where a child entity is loaded only when it is accessed for the first time. Today in this article, we will see how to get started with the Entity Framework Mock and Unit Test DBContext class. I've followed Adam's answer here and the Entity Framework now works and the Seed() method also works. The context is the main class that coordinates Entity Framework functionality for a given data model. It. Treat DbContext class as a session with the database. In the Add Razor Pages using Entity Framework (CRUD) dialog: In the Model class drop-down, select Student (ContosoUniversity.Models). An instance of DbContext represents a session with the database which can be used to query and save instances of your entities to a database.DbContext is a combination of the Unit Of Work and Repository patterns.. DbContext in EF Core allows us to perform following tasks: It simply delays the loading of the related data, until you ask for it. EF 4.1 onwards). In our example, we will define two Context classes for the same database. It simply delays the loading of the related data, until you ask for it. First, install the Nuget package for logging provider of your choice and then tie up the DbContext to ILoggerFactory. All these we discussed in data annotations and here we will see how to achieve the same things using Fluent API. If you leave the default configuration, and dont explicitly tell Entity Framework in your query that you want something other than lazy loading, then lazy loading is what you will get. Entity Framework Mock and Unit Test DBContext. 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