Azure Functions v4绑定CosmosDB提示无法绑定DocumentClient类型错误求解

• Azure Functions v4配套的Cosmos DB v4版本扩展已经完全弃用了旧版Cosmos DB v2 SDK中的Microsoft.Azure.Documents.Client.DocumentClient类型，改为使用Cosmos DB v3 SDK提供的Microsoft.Azure.Cosmos.CosmosClient作为绑定的客户端类型，你当前代码中还在使用已不被支持的DocumentClient进行绑定，所以触发索引报错。
• 旧版本的Functions + Cosmos DB扩展包兼容DocumentClient绑定，所以你之前在.NET Core 3.1的旧环境可以正常运行。

1. 确认你的项目已经正确安装了4.x版本的Microsoft.Azure.WebJobs.Extensions.CosmosDB扩展包，引用命名空间改为Microsoft.Azure.Cosmos，移除旧的Microsoft.Azure.Documents.Client相关引用。
2. 修改Run方法中Cosmos DB的绑定类型，将DocumentClient替换为CosmosClient：

public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "policy")] HttpRequest req,
        [CosmosDB(Connection = "CosmosConnectionString")] CosmosClient cosmos,
        ILogger log)
{
    log.LogInformation("C# HTTP trigger function processed a request.");
    var query = "SELECT * FROM Policy";
    var policies = GetDocumentsByQuery(
       cosmos,
       "AR",
       "Policy",
       query).ToList();
    return new OkObjectResult(policies);
}

3. 同步修改GetDocumentsByQuery方法，适配CosmosClient的API逻辑：

public static List<dynamic> GetDocumentsByQuery(CosmosClient cosmos, string database, string container, string query, string partitionKey = null)
{
    try
    {
        QueryRequestOptions queryOptions;
        if (partitionKey == null)
        {
            queryOptions = new QueryRequestOptions { EnableCrossPartitionQuery = true, PopulateIndexMetrics = true };
        }
        else
        {
            queryOptions = new QueryRequestOptions { PartitionKey = new PartitionKey(partitionKey), PopulateIndexMetrics = true };
        }
        var containerClient = cosmos.GetDatabase(database).GetContainer(container);
        var queryDefinition = new QueryDefinition(query);
        var queryIterator = containerClient.GetItemQueryIterator<dynamic>(queryDefinition, requestOptions: queryOptions);
        var results = new List<dynamic>();
        while (queryIterator.HasMoreResults)
        {
            var response = queryIterator.ReadNextAsync().GetAwaiter().GetResult();
            results.AddRange(response);
        }
        return results;
    }
    catch (Exception)
    {
        throw;
    }
}

内容的提问来源于stack exchange，提问作者nana