Updating specific fields using Entity Framework


Entity framework does a great job of detecting when a field changes on any object that it is tracking. These changes will be automatically saved when SaveChanges is executed. As I discussed in Why the Repository Pattern I like to create an example Generic Class that is type T where T is a Model or a User in my Entity Framework Context. This example will extend upon those context query to retrieve the modified entry.

Table of contents:

Entity Framework update only changed fields

In my Generic Repository class, I often create an entry that looks as follows to set a value on one of my columns in a table on my page:

public void UpdateAndSave(T entity) 
using (var context = new MyContext()) 
context.Entry(entity).State = EntityState.Modified; context.SaveChanges(); 

The following function takes a model of type T. Using the DbContext and the Entry method function, the object’s State is modified to EntityState.Modified. This tells Entity Framework update the entire object in the database. Perfect for 99% of the time when doing an update statement but not for a delete statement.

Update Statement using the IsModified Property values

In the above code, on the rare occasion I want to ensure EF updates 1 or more specific fields of my object and not the entire object with my update method and not an insert statement in the following example.

This can be accomplished by setting the IsModified true property. Let’s take a look at the following update statement for further reading:

        public void UpdateFieldsSave(T entity, params Expression<func<t, object="">>[] includeProperties)
            using (var context = new MyContext())
                var dbEntry = context.Entry(entity);
				foreach (var includeProperty in includeProperties)
					dbEntry.Property(includeProperty).IsModified = true;

This executed dbcommand also takes a model of type T which as an example could be a user with one field. The second parameter is actual an unlimited list of fields. This list will be looped setting the IsModified to true.

Modification of data using DbContext and var context

It depends on what context currently monitors the entity, which may be modified if the entity changes. Typically entities are obtained via contextual information, so contexts start tracking it immediately. The property values of any track entity can be altered by adjusting the context of the Entity state of an entity. ChangeTracker stores the old property values and the new properties. The SaveChanges generates an update statement which executes the database. The ChangeTracker monitors the properties modified so if the property is renamed, it will generate SQL statements.

Once my DbContext is instantiated I fetch the DbEntry based on my model. I then loop the list of properties defined in my input parameter.

Inside the loop each property on my DbEntry each property notifies Entity framework that the property has been modified. When SaveChanges is called, only the properties I identified are updated in the database.

This source code would be executed as follows as db new example:

var repository = new GenericRepository<book>();
var book = repository.GetById(1);
book.Title = "My new title";
repository.UpdateFields(book, b => b.Title);

In this code I instantiate GenericRepository. This class should be created that contains the UpdateFields.

Next the Book model is fetched using a GetById entry. The Title property is changed and I call the UpdateFields entry indicating that I only wish to update that field.

The repository examples are contained on GitHub: https://github.com/endyourif/RepoTest/ source code.

Update Record in EF

Learn how entity frameworks change data from databases. We are capable of restoring data records based on disconnected scenarios. The connected scenario opens the context, queries the entity, changes the entity to a new entity and calls the save Change method. The entity has already been used. We need therefore to just connect the context with this information. Set the state as modified and call the saveChanges. We show you other ways of updating a single record and Related data etc.

Update records in connected scenarios

DBContext assumes responsibility for updating the records. When we query the database the context returns this data and declares the object unchangeable. It then begins monitoring changes to it which is called Change Tracks. When changing an entity, the context is a change in the entity. Adding a new entity in contexts using AddRange is marking it as added. Deleted entities will be marked by the Remover. In the case where saving changes are called – the context will create an insert update and delete SQL command.

Disconnected scenario

In an unconnected scenario like an ASP.NET program, changes can be implemented in controller methods or service methods that can be easily hidden by a context. Typically, the context must know the entity’s changed state. This could happen through a variety of methods: setting the Entity State explicit to a particular entity; and implementing the dbContext. Update mechanism (currently introduced to EF Core). Db context is utilised. Appear methods and then “walk the objects graph” to explicitly specify the status of a specific property on that graph.

DbContext Update

DBContext offers Update and ChangeRange methods for interacting with individual entities. The method will be used to track an entity by context in Modified. Again, the context does nothing to identify property values and generates SQL to update property values. The difference between this method and setting explicitly state property is in the fact that the context will begin monitoring the associated entities in the modified state.

The entity is monitored when changing the environment from one example to another in the example below. It may not always happen when updating disconnected entities in ASP.net Core application. In this case the call to update needs to be made, because the entity was created by the client and not retrieved via the database. It’s impossible to determine whose values change, and marking property properties as modified means that the update takes effect in the event of an item’s changing properties.

Setting EntityState

You can change entity state through EntityEntrance. State assets which can be provided in DbContext. Admission. It is possible that this will only affect author entities with Modified state. Any connected item will not go on. Since ChangeTracker cannot detect what properties have been changed, the context generates an SQL update to the property data (excluding the primary key value).

EF Change tracking

Let me give an overview. This is a typical way for updating e-data from the database to a specific instance. Notice the absence of explicit notification from the email property to be updated to EF. EF identifies these automatic changes and marks them as modified. Consequently, savechanges can only update email columns.

EF Attached Method

In a method attached to an entity, the state of this entity is set to Unchanged and the database command will not run. Similarly, every other reachable entity whose keys are defined can be turned to unchangeable. Those that lack keys are listed as added. The following code is generated to show how the author entity is modified and the SQL generates a new SQL Access query string parameters with Express and Node.js for the same attach method with a new exception or other properties.

Up-dating the var user means obtaining a public int id from the database making any changes needed, then calling save Changes to maintain the changes. There can arise two scenarios when a user updates their information. We have two scenarios in view with public string lastname and var user.

Don’t call Update when you don’t need to!

In my investigation of GitHub, I have a lot of code. A common feature is called DbContexts. Updates or DbSets. Updated if no longer required.

Tell me the reason for putting up the Update call? The update method marks a particular entity’s property as changed. SavingChanges can update Name or Email even when the Name’s value has not changed with int id or var context with the executed dbcommand in the source code.

How do I update a key values in EF?

A simple way of changing existing entities can be achieved in several simple steps. Retrieves an instance of the entity for all the fields. Set and modify its properties by calling Save change with var result and the add method.

Update the record. Updating the entity means getting the entity from the database making the required changes, then calling save changes to persist the changes on the database. Changing the data in the database generates two scenarios.

How do I bulk update EF?

I tested Entity Frameworks. Extension methods update. The updating methods allow bulk updates for records that share the same update values. First load everything. Forge the individual properties and alter the field value. During Foreach saving, the context will be modified once with a sql statement in the following example when updating records.

How do I update EF model after database change code first?

Four responses. Create an Entity DataModel. Stored Database contextTemp or something. First select code from the options in the databases wizard. Select the customer objects and complete a wizard to make it easier.

How do I update EF model from database first?

Right-click the design area and select Update Model in the database. Select the refresh tab of the Updater wizard, then select Tables > DBA > Students. Click Finish. After the update has been completed, the database map shows the new firstname property.

The step of updating an existing new user in a disconnected scenario is fairly easy compared to a connected scenario. Obtain the object instance from the DbSet (the Object Set), edit the properties, then call SaveChanges() to change context if the model is set to Object.

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By Jamie

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