Azure-functions-host: Unable to bind parameter name in external file trigger

[Mauzer93]

When using the external file trigger out of the box it throws an exception:

Exception while executing function: Functions.ExternalFileTriggerCSharp1
Microsoft.Azure.WebJobs.Host.FunctionInvocationException : Exception while executing function: Functions.ExternalFileTriggerCSharp1 ---> System.AggregateException : One or more errors occurred. ---> Exception binding parameter 'name' ---> Binding data does not contain expected value 'name'.
   at Microsoft.Azure.WebJobs.Host.Executors.DelayedException.Throw()
   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithWatchersAsync(IFunctionInstance instance,IReadOnlyDictionary`2 parameters,TraceWriter traceWriter,ILogger logger,CancellationTokenSource functionCancellationTokenSource)
   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??)
   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??)
---> (Inner Exception #0) System.InvalidOperationException : Exception binding parameter 'name' ---> System.InvalidOperationException : Binding data does not contain expected value 'name'.
   at Microsoft.Azure.WebJobs.Host.Bindings.Data.ClassDataBinding`1.BindAsync(BindingContext context)
   at async Microsoft.Azure.WebJobs.Host.Triggers.TriggeredFunctionBinding`1.BindCoreAsync[TTriggerValue](ValueBindingContext context,Object value,IDictionary`2 parameters) 
   End of inner exception<---

---> (Inner Exception #1) System.InvalidOperationException : Exception binding parameter '_return' ---> System.InvalidOperationException : No value for named parameter 'name'.
   at Microsoft.Azure.WebJobs.Host.Bindings.Path.BindingTemplateToken.ExpressionToken.Evaluate(IReadOnlyDictionary`2 bindingData)
   at Microsoft.Azure.WebJobs.Host.Bindings.Path.BindingTemplate.Bind(IReadOnlyDictionary`2 parameters)
   at Microsoft.Azure.WebJobs.Extensions.ApiHub.Common.GenericOutStringFileBinding`2.BindAsync(BindingContext context)
   at async Microsoft.Azure.WebJobs.Host.Triggers.TriggeredFunctionBinding`1.BindCo…

Run.csx

using System;

public static string Run(string inputFile, string name, TraceWriter log)
{
    log.Info($"C# External trigger function processed file: " + name);
    return inputFile;
}

Function.json

{
  "bindings": [
    {
      "type": "apiHubFileTrigger",
      "name": "inputFile",
      "direction": "in",
      "path": "input-cs/{name}",
      "connection": "filesystem_FILESYSTEM"
    },
    {
      "type": "apiHubFile",
      "name": "$return",
      "direction": "out",
      "path": "output-cs/{name}",
      "connection": "filesystem_FILESYSTEM"
    }
  ],
  "disabled": false
}

If I remove the name argument in azure function, the trigger works and I can access the file content, but I am not able to get the file name ... Any ideas on how to fix this?

[safihamid]

This is because you are using a 'File System' connection which is not yet supported. Have you tried using a DropbBox, Box, ... connection? I just tested it and it is working fine with those connections.

[Mauzer93]

Thank you for the clarification. Do you have an idea when the feature will become supported for 'File System'?

[paulmarshall]

I'm also having an issue where the filename of the file that triggered the event (in this case a Dropbox connector) is not available. When is this feature going to be made available?

[safihamid]

It should work for Dropbox connectors. see example above. If not working for you then feel free to share your function.json file as well your code. thanks

[Mauzer93]

@safihamid Is there a timeframe when the external file trigger will be available and working for Azure Function?

[safihamid]

Not at the moment, this was an experimental feature which is not actively being worked on anymore.

[MikeDevMag]

Is this functionality supposed to be working in portal? External File Trigger CSharp? Not able to connect to OneDrive or OneDrive Business in my trials

[satyadevin]

I tried using external file trigger for FTP and it is giving me the below error
[Error] Exception while executing function: Functions.ExternalFileTriggerCSharp1. Microsoft.Azure.WebJobs.Host: One or more errors occurred. Exception binding parameter 'inputFile'. Microsoft.Azure.ApiHub.Sdk: /apim/ftp/098e9d0acab34ac29451e6df6f1ceec6/datasets/default/GetFileContentByPath?path=input-cs/%7Byour%20file%7D.
2019-01-31T10:42:16.448 [Error] Function completed (Failure, Id=1b1ba11f-59af-4665-8c52-78498e61a4fd, Duration=65217ms)

below is my code
{
"bindings": [
{
"type": "apiHubFileTrigger",
"name": "inputFile",
"direction": "in",
"path": "input-cs/{name}",
"connection": "ftp1_FTP"
},
{
"type": "apiHubFile",
"name": "$return",
"direction": "out",
"path": "output-cs/{name}",
"connection": "ftp1_FTP"
}
],
"disabled": false
}

---

r "Microsoft.Azure.WebJobs.Extensions.ApiHub"

using System.Net;
using Microsoft.Azure.WebJobs;

public static string Run(string inputFile, string name, TraceWriter log)
{
log.Info($"C# External trigger function processed file: " + name);
return inputFile;
}