Entity Framework Core and Lazy loading problem

Question

I have project in Entity Framework Core 3.1. When I use lazy loading like this:

services.AddDbContext<IQContext>(options => options.UseLazyLoadingProxies().UseSqlServer(...)

and I call this:

 public async Task<Guid> UpdateAsync(object entity ...)
    {
...
      Type entityType = entity.GetType();
      string primaryKeyName = _dbContext.Model.FindEntityType(entityType).FindPrimaryKey().Properties.Select(x => x.Name).Single();

    }

I got this error:

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Microsoft.EntityFrameworkCore.ModelExtensions.FindEntityType(...) returned null.

But when I remove the UseLazyLoadingProxies(), everything works. Any ideas what can be wrong or how to fix it?

Ivan Stoev · Accepted Answer · 2020-04-17 10:25:34Z

1

Most likely the passed object entity is a proxy instance, in which case GetType() won't be a registered entity type.

Consider replacing FindEntityType with FindRuntimeEntityType:

Gets the entity that maps the given entity class, where the class may be a proxy derived from the actual entity type.

answered Apr 17, 2020 at 10:25

Ivan Stoev

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iknow · Accepted Answer · 2020-09-03 14:12:52Z

0

package-install: Microsoft.EntityFrameworkCore.Proxies

public void ConfigureServices(IServiceCollection services)
{
    #region Database configuration

    // Database configuration
    services.AddDbContext<DbContext>(options =>
        options.UseLazyLoadingProxies()
            .UseSqlServer(Configuration.GetConnectionString("MyConnectionString")));

    #endregion Database configuration
}

edited Sep 3, 2020 at 14:12

iknow

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answered Sep 3, 2020 at 10:59

Saeed Safaee

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