how to update entity when dbcontext changed

Question

using var db = new DbContext(); var entity= new entity(); db.add(entity); db.savechanges(); entity.xxx=yyyy;
cache.set('entity_cache',entity); /------------ other thread---------/ using var db2= new DbContext(); var entity = cache.get('entity_cache'); --------how to update entity

Answer 1

When you retrieve an entity from the cache, it may no longer be tracked by the current DbContext, so you need to attach it to the new context and mark it as modified before saving the changes. Here's an example code snippet that shows how to update the cached entity with a new DbContext:

// Retrieve the cached entity
var cachedEntity = cache.get('entity_cache');

// Create a new DbContext instance
using (var db = new DbContext())
{
    // Attach the cached entity to the new context
    db.Attach(cachedEntity);

    // Update the entity properties
    cachedEntity.Xxx = yyyy;

    // Mark the entity as modified
    db.Entry(cachedEntity).State = EntityState.Modified;

    // Save changes to the database
    db.SaveChanges();
}

Note that it's important to dispose of the DbContext instance after using it to avoid memory leaks. Also, make sure to call Attach() on the context before modifying the entity, otherwise, the changes won't be tracked and saved to the database. I hope this will help.