ef

Boostig Entity Framework Loops

public class Product {

        public int ID { get; set; }

        public string ShortDescription { get; set; }

}

public class OldVariation {

        public int ID { get; set; }

        public int ProductID { get; set; }

        public virtual ProductModel Product { get; set; }      

}

public class Variation {

        public int ID { get; set; }

        public int ProductID { get; set; }

        public virtual Product Product { get; set; }

}

var db = new AppContext();

var oldVariations= db.OldVariations.ToList();

foreach (var item in oldVariations )

{

var variation = new VariationModel

{

ProductID = item.ProductID ,

Description = item.Product.Description, //because of lazy loading, entity framework is querying the database!

ShortDescription = item.Product.ShortDescription , //because of lazy loading, entity framework is querying the database!//because of lazy loading, entity framework is querying the database!

        };

        

        //if validations pass

        db.Variations.Add(variation);

        db.SaveChanges();

}

This scenario takes ages if the number of OldVariations is very very large. Improvements:

var db = new AppContext();

var oldVariations= db.OldVariations.Include(o=>o.Product).ToList();

 var counter = 0;

var threshold = 50;

db.Configuration.AutoDetectChangesEnabled = false;

foreach (var item in oldVariations )

{

var variation = new VariationModel

{

ProductID = item.ProductID ,

Description = item.Product.Description, //because of eager loading, entity framework is NOT querying the database

ShortDescription = item.Product.ShortDescription , /because of eager loading, entity framework is NOT querying the database

};

        

        //if validations pass

        db.Variations.Add(variation);

          counter++;

if (counter >= threshold)

{

db.SaveChanges();

db.Dispose();

db = new AppContext();

db.Configuration.AutoDetectChangesEnabled = false;

counter = 0;

} 

}

       db.SaveChanges();

Create Unique Index with Column that Accepts Null Values in Entity Framework Migration

Sql("CREATE UNIQUE NONCLUSTERED INDEX [IX_ColumnWithNulls]  ON [dbo].[Table]([ColumnWithNulls] ASC) WHERE ([ColumnWithNulls] IS NOT NULL");

Sql("CREATE UNIQUE NONCLUSTERED INDEX IX_Number on dbo.Orders(Number,ID) where Number IS NOT NULL");

Resetting Entity Framework Migrations to a clean Slate

By Rick Strahl

       public string Description { get; set; }

       public string ShortDescription { get; set; }

       public string Description { get; set; }

Windows Service with Code First Migrations Error

Getting an error of the type "System.InvalidOperationException: The model backing the 'Context' context has changed since the database was created. Consider using Code First Migrations to update the database " and the migrations are up to date and handled by another project.

In fact, the error is because the user running the windows service does not have sufficient privileges! Try setting up a different Windows service login account from the service properties.

EF, SQL Spatial and ClassLibrary Project for Models and Web App Project Referencing the ClassLibrary Project

ClassLibrary Project contains context and models linked to database by Entity Framework.

In order to use DBGeography I needed:

SqlServerTypes.Utilities.LoadNativeAssemblies(Server.MapPath("~/bin"));

  SqlProviderServices.SqlServerTypesAssemblyName =

    "Microsoft.SqlServer.Types, Version=14.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91";


In order to re-copy assemblies to bin folder, you first need to stop IIS!!!

Error Migrating on AddOrUpdate(p => new {  p.KeyID, p.ValID }...   Where ValID is Nullable Int

Make sure Entity framework is above 6.2.0


EF, SQL Spatial and ClassLibrary Project for Models and Windows Service Referencing the ClassLibrary Project

ClassLibrary Project contains context and models linked to database by Entity Framework with DBGeography.

Initially:

When trying to write DB from Windows Service I get error  "Exception: System.InvalidOperationException: Spatial types and functions are not available for this provider because the assembly 'Microsoft.SqlServer.Types' version 10 or higher could not be found.     en System.Data.Entity.SqlServer.SqlTypesAssemblyLoader.GetSqlTypesAssembly()    en System.Data.Entity.SqlServer.SqlSpatialServices.GeometryFromText(String wellKnownText)    en System.Data.Entity.Spatial.DbGeometry.FromText(String wellKnownText)    en System.Data.Entity.Core.Mapping.Update.Internal.Propagator.ExtentPlaceholderCreator.InitializeSpatialTypeDefaultMap()..."


In order to use DBGeography in Windows Service I needed: