EF Core 中的当前上下文中不存在名称 Savechanges()

Question

I am migrating my code from EF to EF Core. We do have an Igenericreposirory. And this Igenericreposirory is inheriting by Genericreposirory.

IGenericreposirory

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;

namespace DataLayer.Repositories.Base
{
public interface IGenericRepository<T, TKey> where T : class
{
       T Add(T entity);
}
}

GenericRepository:

public class GeneralRepository<T, TKey> : IGenericRepository<T, TKey>
    where T : class, IEntity<TKey>, new()
 {
    protected readonly DbContext DbContext;
    internal DbSet<T> DbSet;

    public GeneralRepository(DbContext dbContext)
    {
        if (dbContext == null)
            throw new ArgumentNullException("dbContext");

        this.DbContext = dbContext;

        this.DbSet = this.DbContext.Set<T>();
    }

public virtual T Add(T entity)
    {
        #region Argument Validation

        if (entity == null)
        {
            throw new ArgumentNullException("entity");
        }

        #endregion

        var obj = DbSet.Add(entity);
        SaveChanges();
        return obj;
    }

}

Here I am getting 2 errors while working with EF core 1 at return obj as "Cannot convert from 'Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry' to 'T'"

2 at Savechange() as "the name savechanges()" does not exists in the current context.

As far as i know, EF core supports all methods to fetch, Insert, ADD

Answer 1

1 at return obj as "Cannot convert from 'Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry' to 'T'"

The signature of DbSet.Add() has been changed between EF6 and EF core. In EF6 it returned the entity itself, see the documentation of DbSet.Add() in EF6 :

 public virtual TEntity Add (TEntity entity);

But in EF core it has been changed to return an EntityEntry object instead, see the documentation of DbSet.Add() in EF core :

 public virtual Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry<TEntity> Add (TEntity entity);

So you have to return the value of the EntityEntry.Entity property to get the tracked entity (which might be the same as your entity variable). So the code might look like this:

var obj = DbSet.Add(entity);
// [...]
return obj.Entity;

2 at Savechange() as "the name savechanges()" does not exists in the current context.

Your are trying to call a method SaveChanges(); on your class GeneralRepository , but there is no such method defined. However, the DbContext object has such a method . Simply call the method from your DbContext instead:

var obj = DbSet.Add(entity);
this.Context.SaveChanges();
return obj.Entity;