Azure Function V4 .NET隔离模式下如何读写CosmosDB？

前置准备 #

• 安装NuGet包：Microsoft.Azure.Cosmos（直接使用Cosmos官方SDK，不再依赖WebJobs特性）
• 在local.settings.json或Azure配置中添加CosmosDB连接字符串，示例命名为CosmosDbConnectionString

读取函数（根据documentId查询） #

创建HTTP触发函数，通过构造函数注入CosmosClient，利用SDK直接读取目标文档：

using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Http;
using Microsoft.Azure.Cosmos;
using System.Net;

public class CosmosDbReadFunction
{
    private readonly CosmosClient _cosmosClient;
    private readonly string _databaseId = "你的数据库ID";
    private readonly string _containerId = "你的容器ID";

    public CosmosDbReadFunction(CosmosClient cosmosClient)
    {
        _cosmosClient = cosmosClient;
    }

    [Function("GetMyDocById")]
    public async Task<HttpResponseData> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", Route = "mydoc/{documentId}")] HttpRequestData req,
        string documentId)
    {
        var container = _cosmosClient.GetContainer(_databaseId, _containerId);
        
        try
        {
            // 此处假设分区键与documentId一致，需根据实际容器配置调整
            var response = await container.ReadItemAsync<MyDoc>(documentId, new PartitionKey(documentId));
            var res = req.CreateResponse(HttpStatusCode.OK);
            await res.WriteAsJsonAsync(response.Resource);
            return res;
        }
        catch (CosmosException ex) when (ex.StatusCode == HttpStatusCode.NotFound)
        {
            var res = req.CreateResponse(HttpStatusCode.NotFound);
            await res.WriteStringAsync("文档不存在");
            return res;
        }
    }
}

public class MyDoc
{
    public string Id { get; set; }
    // 自定义其他业务属性
}

写入函数（接收MyDoc并写入） #

通过Cosmos SDK执行Upsert操作（自动处理创建或更新）：

using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Http;
using Microsoft.Azure.Cosmos;
using System.Net;
using System.Text.Json;

public class CosmosDbWriteFunction
{
    private readonly CosmosClient _cosmosClient;
    private readonly string _databaseId = "你的数据库ID";
    private readonly string _containerId = "你的容器ID";

    public CosmosDbWriteFunction(CosmosClient cosmosClient)
    {
        _cosmosClient = cosmosClient;
    }

    [Function("CreateOrUpdateMyDoc")]
    public async Task<HttpResponseData> Run(
        [HttpTrigger(AuthorizationLevel.Function, "post", Route = "mydoc")] HttpRequestData req)
    {
        var myDoc = await JsonSerializer.DeserializeAsync<MyDoc>(req.Body);
        if (myDoc == null || string.IsNullOrEmpty(myDoc.Id))
        {
            var res = req.CreateResponse(HttpStatusCode.BadRequest);
            await res.WriteStringAsync("无效的文档数据，Id不能为空");
            return res;
        }

        var container = _cosmosClient.GetContainer(_databaseId, _containerId);
        // Upsert自动判断文档是否存在，存在则更新，不存在则创建
        var response = await container.UpsertItemAsync(myDoc, new PartitionKey(myDoc.Id));

        var res = req.CreateResponse(HttpStatusCode.Created);
        await res.WriteAsJsonAsync(response.Resource);
        return res;
    }
}

配置CosmosClient依赖注入 #

在Program.cs中注册CosmosClient，确保可通过构造函数注入：

using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWorkerDefaults()
    .ConfigureServices(services =>
    {
        services.AddSingleton<CosmosClient>(sp =>
        {
            var configuration = sp.GetRequiredService<IConfiguration>();
            var connectionString = configuration["CosmosDbConnectionString"];
            return new CosmosClient(connectionString);
        });
    })
    .Build();

host.Run();

关键说明 #

• 不再依赖WebJobs的[CosmosDB]特性，直接使用官方Cosmos SDK，灵活性更强
• 依赖注入CosmosClient是推荐方案，避免重复创建客户端实例导致资源浪费
• 分区键需与容器配置完全匹配，示例中假设分区键为Id，需根据实际场景调整
• 若仅需创建文档可使用CreateItemAsync，仅更新则用ReplaceItemAsync，UpsertItemAsync为通用场景最优选择

内容的提问来源于stack exchange，提问作者AndyW