Azure Cosmos DB- SQL API using EF Core- Part two


In my previous article, we have seen the introduction of the Cosmos DB. If you haven’t read my previous article then I highly encourage you to do so

Azure Cosmos DB CLI

Let’s begin with creating Azure resources using CLI

az login

//Resource group creation
az group create -l southindia -n $resourcegroup

//Cosmos DB Account creation
az cosmosdb create -n $name -g $resourcegroup --default-consistency-level Session 

//Cosmosdb creation
az cosmosdb sql database create -a $name -n $name -g $resourcegroup --throughput 400

Firstly, after running az login, CLI will open your default browser and load an Azure sign-in page. Thereafter, the user has to sign-in.

In the second part, we are creating resource group with the name “CosmosDBVerify” by running the below script

//Resource group creation
az group create -l southindia -n $resourcegroup

Next, we are creating the Cosmos DB account by using the below script

az cosmosdb create -n $name -g $resourcegroup --default-consistency-level Session 

Lastly, we are creating SQL Cosmos DB by using

az cosmosdb sql database create -a $name -n $name -g $resourcegroup --throughput 400

Here I want to be more specific about throughput, so setting it to 400 RU. Default value of throughput is 400 RU.

Note: As of today(July 5th, 2020), Microsoft is providing free Cosmos DB account for preview. you can utilise that as well by going directly here


In this article, I’m using a classic example of maintaining a user/employee profile such as information about his current company, previous companies etc.

Without wasting much time, let’s begin by creating a .net core console application. Firstly, add Microsoft.EntityFrameworkCore.Cosmos nuget package.

let create an entity classes

public class Profile
        public string Title { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string DOB { get; set; }
        public string PhoneNumber { get; set; }
        public string Designation { get; set; }
        public Company CurrentCompany { get; set; }
        public string HighestEducation { get; set; }
        public ICollection<Company> PreviousCompanies { get; set; }
        public string UserId { get;  set; }
public class Company
        public string CompanyName { get; set; }
        public DateTime StartDate { get; set; }
        public DateTime EndDate { get; set; }
        public bool IsActive { get; set; }

Instead of using Data Annotations, I would like to use Fluent API for certain reasons

  • Data Annotation violates Separation of Concerns principle and couples persistence layer with domain model logic.
  • Fluent API decouples my models from Entity Framework.
  • It provides more options of configurations than Data Annotation attributes.

Now, we can configure the mappings between these two entities by using IEntityTypeConfiguration<T> interface as follows.

public class ProfileEntityConfiguration:IEntityTypeConfiguration<Profile>
        public void Configure(EntityTypeBuilder<Profile> builder)
            builder.HasKey(x => x.UserId);
            builder.HasPartitionKey(x => x.UserId);
            builder.OwnsOne(x => x.CurrentCompany);
            builder.OwnsMany(x => x.PreviousCompanies);
HasKeyIt is used to denote the property that uniquely identifies an entity. This is mainly the Primary key of the table.
HasPartitionKeyIt is used to store the partition key. In my example, I have used UserId as the partition key
OwnsOneIt is used to define one-one mapping between tables.
OwnsManyIt is used to define one-many mappings between tables

After creating that class with the necessary customizations, you need to wire that up to your DbContext’s OnModelCreating method by calling modelBuilder.ApplyConfiguration(new ConfigClass())

public class ProfileContext:DbContext
        public DbSet<Profile> Profiles { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
            var accountEndpoint = "";
            var accountKey = "";
            var dbName = "";
            optionsBuilder.UseCosmos(accountEndpoint, accountKey, dbName);

        protected override void OnModelCreating(ModelBuilder modelBuilder)
            modelBuilder.ApplyConfiguration(new ProfileEntityConfiguration());

Now writing our required logic in the main method

static void Main(string[] args)
            var context = new ProfileContext();
            context.Profiles.Add(new Profile
                UserId = Guid.NewGuid().ToString(),
                CurrentCompany = new Company
                    CompanyName = "Infosys",
                    StartDate = DateTime.Today,
                    IsActive = true
                PreviousCompanies=new List<Company>
                    new Company

To keep it simple, I have directly used DbContext in the main program but I would highly recommend you to implement repository pattern.

Note: Ef Core doesn’t support migration for Cosmos DB. In the above main function, I have used context.Database.EnsureCreated() to ensure whether the Cosmos DB is in sync with the entity classes.

In the next article, we’ll look into Geo-replication by using this example in the .net core API.

I hope you like the article. In case, you find the article interesting then kindly like and share it.

2 thoughts on “Azure Cosmos DB- SQL API using EF Core- Part two

  1. Pingback: Azure Cosmos DB-SQL API Geo Replication using EF Core- Part Three – Articles on latest .net technology

  2. Pingback: Query and Mutation in GraphQL- Part two – Articles on latest .net technology

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