Azure function HTTP trigger Blob storage output binding-CodePudding

I try to develop HTTP trigger azure function using C# and .net 3.0.1 (runtime ~3) and Visual Studio 2019. In my function I want to write data into blob and I want to be able set destination file name from request body. I use the following code:

public static async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req,
            [Blob("reports/{reportname}", FileAccess.Write)] TextWriter report,
            ILogger log)
        {

But when I run function, I got error:

Unable to resolve binding parameter 'reportname'. Binding expressions must map to either a value provided by the trigger or a property of the value the trigger is bound to, or must be a system binding expression (e.g. sys.randguid, sys.utcnow, etc.).

I already read about bindings but I completely don't understand how to create correct binding or how to add binding into function.json file.

Can anyone please help/explain what do I do wrong?

Thanks!

CodePudding user response：

Firstly, you need to provide a value for {reportname} as the error message says.

As you are using a [HttpTrigger], you can provide the value in a POST request body:

{
    "reportName": "test"
}

In the [HttpTrigger] binding, instead of getting a HttpRequest object, you can get the binding to pass you a deserialized object to represent your POST request i.e. MyRequest:

[HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] MyRequest request

When you send a request, the ReportName property will then get mapped in the [Blob] binding to the path: reports/{reportname}. This is the path in blob storage where your file will be stored.

You can then use the output TextWriter report parameter to add text to your blob:

report.WriteLineAsync("content");

Or you may wish to also send the report content in the POST body:

public class MyRequest
{
    public string ReportName { get; set; }

    public string ReportContent { get; set; }
}

report.WriteLineAsync(request.ReportContent);

Full working example:

public static class HttpTriggeredFunction
{
    [FunctionName("HttpTriggeredFunction")]
    public static async Task<IActionResult> Run(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = "reports")] MyRequest request,
        [Blob("reports/{reportname}", FileAccess.Write)] TextWriter report,
        ILogger log)
    {
        await report.WriteLineAsync(request.ReportContent);

        return new OkResult();
    }
}

public class MyRequest
{
    public string ReportName { get; set; }

    public string ReportContent { get; set; }
}