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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:

• • eager load product

  • save and dispose db context every n loops

• context.Configuration.AutoDetectChangesEnabled = false

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