For a while now, I’ve been using the excellent LINQPad to quickly run .Net Entity Framework queries using the actual object model and database mappings from one of my projects, via a DbContext connection pointed to my project’s compiled .dll file and web.config file set up in LINQPad.
Recently, after this having been working fine for a while, I started getting an error when trying to execute any queries using this DbContext connection in LINQPad:
The default DbConfiguration instance was used by the Entity Framework before the '...' type was discovered.The "..." in that error message was actually the name of a new class that had been added to my .Net project, which derived from the DbConfiguration class.
The fix was, in my project’s web.config file, to add to the entityFramework element a codeConfigurationType attribute pointing to the new class and its package. So, whereas before my web.config file had:
<entityFramework>
...
</entityFramework>
I changed it to:
<entityFramework codeConfigurationType="MyProject.MyPackage.MyCustomDBConfiguration, MyProject.MyPackage">
...
</entityFramework>
(Where "MyProject", "MyPackage", and "MyCustomDBConfiguration" all obviously are replaced by the actual project, package, and class names from my actual project.)
With that change in place, I was able to successfully execute queries using my project’s EF model once again.
Update 2016-06-06: A second possible cause of this same issue is if the path to your application config file (or web.config file) in LinqPad's Connection Properties dialog is incorrect.
I had this issue occur just now after moving my project to a new location on disk. I'd corrected the "Path to Custom Assembly" value in the Connection Properties dialog, but I initially neglected to make the corresponding filesystem path change to the the "Path to application config" value.
Posts
Exactly my issue. Thanks!
ReplyDeleteJonathan, where can I find what to enter instead of: "MyProject", "MyPackage", and "MyCustomDBConfiguration"?
ReplyDeleteI don't know what to replace it with..
Jonas, in my case, "MyCustomDbConfiguration" was the name of my class that inherits from DbConfiguration, and "MyProject.MyPackage" is the fully-specified namespace in which that class resides. Sorry it was unclear!
ReplyDeleteIt works perfectly!! Thanks!
ReplyDeleteThanks for the good explanation.
ReplyDeletei updated my context file to
ReplyDelete//------------------------------------------------------------------------------
//
// This code was generated from a template.
//
// Manual changes to this file may cause unexpected behavior in your application.
// Manual changes to this file will be overwritten if the code is regenerated.
//
//------------------------------------------------------------------------------
namespace MrSales.MrSModels
{
using System;
using System.Data.Entity;
using System.Data.Entity.Infrastructure;
using System.Data.Entity.Core.Objects;
using System.Linq;
using System.Data.Common;
public partial class mrsalesdbEntities : DbContext
{
public mrsalesdbEntities()
: base("name=mrsalesdbEntities")
{
}
public mrsalesdbEntities(DbConnection existingConnection, bool contextOwnsConnection)
: base(existingConnection, contextOwnsConnection)
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
throw new UnintentionalCodeFirstException();
}
public virtual DbSet account_items { get; set; }
also i updated the app.config file to:
but this error appear :
The DbConfiguration type 'MrSales.MrSModels.mrsalesdbEntities, MrSales.MrSModels' specified in the application config file could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260883 for more information.'