1# Cosmos DB Recipe — C# (.NET) — REFERENCE ONLY
2 
3## Cosmos DB SDK Setup
4 
5### NuGet Packages
6 
7```xml
8<PackageReference Include="Microsoft.Azure.Cosmos" Version="3.*" />
9<PackageReference Include="Azure.Identity" Version="1.13.*" />
10```
11 
12### Program.cs (additions)
13 
14Add these lines — do NOT replace the existing file:
15 
16```csharp
17using Azure.Identity;
18using Microsoft.Azure.Cosmos;
19 
20builder.Services.AddSingleton(_ =>
21{
22    var endpoint = builder.Configuration["COSMOS_ENDPOINT"];
23    return new CosmosClient(endpoint, new DefaultAzureCredential());
24});
25```
26 
27### CRUD Endpoints
28 
29Add to `Program.cs` after `app` is built:
30 
31```csharp
32app.MapGet("/api/items", async (CosmosClient cosmos) =>
33{
34    var container = cosmos
35        .GetDatabase(Environment.GetEnvironmentVariable("COSMOS_DATABASE_NAME"))
36        .GetContainer(Environment.GetEnvironmentVariable("COSMOS_CONTAINER_NAME"));
37    var query = container.GetItemQueryIterator<dynamic>("SELECT * FROM c");
38    var results = new List<dynamic>();
39    while (query.HasMoreResults)
40        results.AddRange(await query.ReadNextAsync());
41    return Results.Ok(results);
42});
43```
44 
45## Files to Modify
46 
47| File | Action |
48|------|--------|
49| `Program.cs` | Add CosmosClient registration + endpoints |
50| `*.csproj` | Add Microsoft.Azure.Cosmos NuGet package |
51