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

Error binding Blob to IAsyncCollector when binding to output blob in Async method(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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