在 Async 方法中绑定到输出 blob 时，将 Blob 绑定到 IAsyncCollector 时出错

问题描述

我正在尝试在这篇文章之后以异步方法绑定到 blob 输出:如何将输出值绑定到我的异步 Azure 函数?

I'm trying to bind to a blob output in an Async method following this post: How can I bind output values to my async Azure Function?

我有多个输出绑定，所以只返回不是一个选项

I have multiple output bindings so just returning is not an option

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, IAsyncCollector<string> collection, TraceWriter log)
{
    if (req.Method == HttpMethod.Post) 
    {
        string jsonContent = await req.Content.ReadAsStringAsync();

        // Save to blob 
        await collection.AddAsync(jsonContent);

        return req.CreateResponse(HttpStatusCode.OK);
    }
    else 
    {
        return req.CreateResponse(HttpStatusCode.BadRequest);

    }
}

我对 blob 的绑定是:

My binding for the blob is :

{
  "bindings": [
    {
      "authLevel": "function",
      "name": "req",
      "type": "httpTrigger",
      "direction": "in"
    },
    {
      "name": "$return",
      "type": "http",
      "direction": "out"
    },
    {
      "type": "blob",
      "name": "collection",
      "path": "testdata/{rand-guid}.txt",
      "connection": "test_STORAGE",
      "direction": "out"
    }
  ],
  "disabled": false
}

但每当我这样做时，我都会得到以下信息:

But whenever I do this I get the following:

错误:函数($WebHook)错误:Microsoft.Azure.WebJobs.Host:索引方法错误'Functions.WebHook'.Microsoft.Azure.WebJobs.Host:无法绑定要键入的 Blob'Microsoft.Azure.WebJobs.IAsyncCollector`1[System.String]'

Error: Function ($WebHook) Error: Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.WebHook'. Microsoft.Azure.WebJobs.Host: Can't bind Blob to type 'Microsoft.Azure.WebJobs.IAsyncCollector`1[System.String]'

推荐答案

Blob 输出绑定不支持收集器，请参阅此 问题.

Collectors are not supported for Blob output bindings, see this issue.

对于可变数量的输出 blob(在您的情况下为 0 或 1，但可以是任意数量)，您必须使用命令式绑定.从您的 function.json 中删除 collection 绑定，然后执行以下操作:

For variable amount of output blobs (0 or 1 in your case, but can be any), you would have to use imperative bindings. Remove collection binding from your function.json and then do this:

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, Binder binder)
{
    if (req.Method == HttpMethod.Post) 
    {
        string jsonContent = await req.Content.ReadAsStringAsync();

        var attributes = new Attribute[]
        {    
            new BlobAttribute("testdata/{rand-guid}.txt"),
            new StorageAccountAttribute("test_STORAGE")
        };

        using (var writer = await binder.BindAsync<TextWriter>(attributes))
        {
            writer.Write(jsonContent);
        }

        return req.CreateResponse(HttpStatusCode.OK);
    }
    else 
    {
        return req.CreateResponse(HttpStatusCode.BadRequest);    
    }
}

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