C#: Basic exercise using Entity Framework Core provider for PostgreSQL

Author: amotl

.github/dependabot.yml

@@ -33,6 +33,11 @@ updates:
     schedule:
       interval: "daily"
 
+  - directory: "/by-language/csharp-efcore"
+    package-ecosystem: "nuget"
+    schedule:
+      interval: "daily"
+
   - directory: "/by-language/csharp-npgsql"
     package-ecosystem: "nuget"
     schedule:

.github/workflows/lang-csharp-efcore.yml

@@ -0,0 +1,81 @@
+name: C# EF Core
+
+on:
+  pull_request:
+    paths:
+    - '.github/workflows/lang-csharp-efcore.yml'
+    - 'by-language/csharp-efcore/**'
+    - '/requirements.txt'
+  push:
+    branches: [ main ]
+    paths:
+    - '.github/workflows/lang-csharp-efcore.yml'
+    - 'by-language/csharp-efcore/**'
+    - '/requirements.txt'
+
+  # Allow job to be triggered manually.
+  workflow_dispatch:
+
+  # Run job each night after CrateDB nightly has been published.
+  schedule:
+    - cron: '0 3 * * *'
+
+# Cancel in-progress jobs when pushing to the same branch.
+concurrency:
+  cancel-in-progress: true
+  group: ${{ github.workflow }}-${{ github.ref }}
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  test:
+    name: "
+     .NET: ${{ matrix.dotnet-version }}
+     CrateDB: ${{ matrix.cratedb-version }}
+     on ${{ matrix.os }}"
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ 'ubuntu-22.04' ]
+        dotnet-version: [ '9.0.x' ]
+        cratedb-version: [ 'nightly' ]
+
+    # https://docs.github.com/en/free-pro-team@latest/actions/guides/about-service-containers
+    services:
+      cratedb:
+        image: crate/crate:${{ matrix.cratedb-version }}
+        ports:
+          - 4200:4200
+          - 5432:5432
+        env:
+          CRATE_HEAP_SIZE: 4g
+
+    steps:
+
+      - name: Acquire sources
+        uses: actions/checkout@v4
+
+      - name: Set up .NET ${{ matrix.dotnet-version }}
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: ${{ matrix.dotnet-version }}
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+          architecture: x64
+          cache: 'pip'
+          cache-dependency-path: |
+            requirements.txt
+
+      - name: Install utilities
+        run: |
+          pip install -r requirements.txt
+
+      - name: Validate by-language/csharp-efcore
+        run: |
+          ngr test by-language/csharp-efcore --dotnet-version=${{ matrix.dotnet-version }}

by-language/csharp-efcore/.gitignore

@@ -0,0 +1,4 @@
+*.user
+bin
+obj
+TestResults

by-language/csharp-efcore/BlogDemo.cs

@@ -0,0 +1,79 @@
+// Example program for EFCore with CrateDB.
+
+// Npgsql Entity Framework Core provider for PostgreSQL
+// https://github.com/npgsql/efcore.pg
+using System;
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+
+public class Blog
+{
+    public long Id { get; set; }
+    public required string Name { get; set; }
+}
+
+public class BloggingContext : DbContext
+{
+    public DbSet<Blog> Blogs { get; set; }
+
+    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+        => optionsBuilder.UseNpgsql(@"Host=localhost;Username=crate;Password=;Database=testdrive");
+}
+
+class BlogDemo
+{
+    public BloggingContext context;
+    
+    public static void Main(string[] args)
+    {
+        var blogDemo = new BlogDemo();
+        blogDemo.run();
+    }
+
+    public BlogDemo()
+    {
+        // Provide context and turn off transactions.
+        context = new BloggingContext();
+        context.Database.AutoTransactionBehavior = AutoTransactionBehavior.Always;
+        context.Database.AutoSavepointsEnabled = false;
+
+        // CrateDB does not implement 'DROP DATABASE'.
+        // await context.Database.EnsureDeleted();
+        context.Database.EnsureCreated();
+    }
+
+    public void run()
+    {
+        RunDDL();
+        EfCoreWorkload();
+    }
+
+    public void RunDDL()
+    {
+        context.Database.ExecuteSqlRaw("""
+            CREATE TABLE IF NOT EXISTS "Blogs" 
+            ("Id" bigint GENERATED ALWAYS AS NOW(), "Name" text);
+        """);
+    }
+
+    public void EfCoreWorkload()
+    {
+
+        // Insert a Blog.
+        context.Blogs.Add(new() { Name = "FooBlog" });
+        context.SaveChanges();
+
+        // For converging written data immediately, submit a cluster-wide flush operation.
+        // https://cratedb.com/docs/crate/reference/en/latest/sql/statements/refresh.html#sql-refresh
+        context.Database.ExecuteSqlRaw("""REFRESH TABLE "Blogs";""");
+
+        // Query all blogs whose name starts with F.
+        var fBlogs = context.Blogs.Where(b => b.Name.StartsWith("F")).ToList();
+
+        // Output the results to the console.
+        foreach (var blog in fBlogs)
+        {
+            Console.WriteLine($"Blog Id: {blog.Id}, Blog Name: {blog.Name}");
+        }
+    }
+}

by-language/csharp-efcore/README.md

@@ -0,0 +1,44 @@
+# Npgsql Entity Framework Core provider for PostgreSQL with CrateDB
+
+## About
+
+The file `BlogDemo.cs` includes a demonstration program written in [C#] which
+demonstrates the [Entity Framework Core] README code snippet of [efcore.pg],
+effectively a very basic usage scenario, with CrateDB.
+
+`efcore.pg` is built on top of [Npgsql - .NET Access to PostgreSQL].
+
+## Usage
+
+Start a CrateDB instance for evaluation purposes.
+```shell
+docker run -it --rm --publish=4200:4200 --publish=5432:5432 crate:latest
+```
+
+Invoke example program.
+```shell
+dotnet run
+```
+
+## Tests
+
+Invoke software tests.
+```shell
+dotnet test
+```
+
+Generate a Cobertura code coverage report.
+```shell
+dotnet test --collect:"XPlat Code Coverage"
+```
+
+Invoke test cases selectively.
+```shell
+dotnet test --filter BlogDemoTest
+```
+
+
+[C#]: https://en.wikipedia.org/wiki/C_Sharp_(programming_language)
+[efcore.pg]: https://github.com/npgsql/efcore.pg
+[Entity Framework Core]: https://learn.microsoft.com/en-gb/ef/core/
+[Npgsql - .NET Access to PostgreSQL]: https://github.com/npgsql/npgsql

by-language/csharp-efcore/backlog.md

@@ -0,0 +1,5 @@
+# Backlog for Entity Framework Core for PostgreSQL with CrateDB
+
+- Provide test rig for all data types of CrateDB, like `DemoTypes.cs` of `csharp-npgsql`.
+- Can DDL statements be derived from the model, and automatically be applied?
+- Can models be derived by introspecting the database?

by-language/csharp-efcore/demo.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net$(NETCoreAppMaximumVersion)</TargetFramework>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
+    <GenerateProgramFile>false</GenerateProgramFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
+    <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="9.0.4" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.0.2" />
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+  </ItemGroup>
+
+</Project>

by-language/csharp-efcore/tests/BlogDemoTest.cs

@@ -0,0 +1,40 @@
+using System.Data;
+using Microsoft.EntityFrameworkCore;
+using Npgsql;
+using Xunit;
+
+public class BlogDemoTest
+{
+    public NpgsqlConnection GetConnection(string? connectionString)
+    {
+        var dataSourceBuilder = new NpgsqlDataSourceBuilder(connectionString);
+        // dataSourceBuilder.EnableDynamicJson();
+        using var dataSource = dataSourceBuilder.Build();
+        return dataSource.OpenConnection();
+    }
+
+    [Fact]
+    public void TestBlogDemo()
+    {
+        // Invoke example database workload.
+        var blogDemo = new BlogDemo();
+        blogDemo.run();
+
+        // Validate database content.
+        var conn = GetConnection(blogDemo.context.Database.GetConnectionString());
+        var cmd = new NpgsqlCommand("""SELECT * FROM testdrive."Blogs";""", conn);
+        var reader = cmd.ExecuteReader();
+
+        var data = new DataTable();
+        data.Load(reader);
+        
+        // Check first record.
+        var row = data.Rows[0];
+        Assert.NotNull(row["Id"]);
+        Assert.Equal("FooBlog", row["Name"]);
+        
+        conn.Close();
+        conn.Dispose();
+    }
+    
+}