Parallel.ForEachAsync ExecuteWebRequestAsync Object reference not set to an instance of an object

[Marvinnnne]

In a simple loop, ExecuteWebRequestAsync works but in a Parallel.ForEachAsync, it doesn't work and i don't understand why.
Is there something I'm missing in parallelism ?

Thanks for your help

[MattB-msft]

Would need to see more of the Stack trace to see where this is going wrong..
that said you should add some null checks into your use of each param your passing into the method call to verify that they are all valid in that iteration.

[Marvinnnne]

Here the stack trace :
System.NullReferenceException
HResult=0x80004003
Message=Object reference not set to an instance of an object.
Source=Microsoft.PowerPlatform.Dataverse.Client
StackTrace:
at Microsoft.PowerPlatform.Dataverse.Client.ConnectionService.<Command_WebExecuteAsync>d__191.MoveNext()
at Microsoft.PowerPlatform.Dataverse.Client.ServiceClient.d__147.MoveNext()
at Unibail.InterfaceIncomingSnowflake.AppConsole.<>c__DisplayClass52_0.<b__0>d.MoveNext() in C:\Users\marvin.leemans-dolo\source\repos\URW CRM\Solutions\Core\Unibail.InterfaceIncomingSnowflake\AppConsole.cs:line 438

This exception was originally thrown at this call stack:
[External Code]
Unibail.InterfaceIncomingSnowflake.AppConsole.ExecuteWebApiRequest.AnonymousMethod__0(Unibail.InterfaceIncomingSnowflake.CSVHelper.InputSnowflake, System.Threading.CancellationToken) in AppConsole.cs

And I add the null check and nothing is null

Don't hesitate if you need something

[MattB-msft]

I would suggest reading though this first. : https://learn.microsoft.com/en-us/power-apps/developer/data-platform/send-parallel-requests?tabs=sdk#using-serviceclient-with-net-6-or-higher

We will take a look a the use of executewebrequest in this pattern, it's not something we have emphasized as its slower than the organization request pattern.

[Marvinnnne]

I know it's better to use List but because historic constraint, the format is web api. It's more difficult to change all interface to entity than try to push the web api.

Thanks for your help

[MattB-msft]

Marvinnnne
Sorry for the delay,, Iv finally gotten some time to dig into this.

I am using DVSC v1.2.3, targeting .net 8.0

I created a repro of your process:

            List<WebApiRequest> webApiRequests = new List<WebApiRequest>();
            webApiRequests.Add(new WebApiRequest() { RequestUri = "contacts", Method = "GET", Content = "" });
            webApiRequests.Add(new WebApiRequest() { RequestUri = "accounts", Method = "GET", Content = "" });
            webApiRequests.Add(new WebApiRequest() { RequestUri = "systemusers", Method = "GET", Content = "" });

            var token = CancellationToken.None;
            await Parallel.ForEachAsync(
                source: webApiRequests,
                parallelOptions: new ParallelOptions() { MaxDegreeOfParallelism = client.RecommendedDegreesOfParallelism },
                async (webApiRequest, token) =>
                {

                    var httpMethod = new HttpMethod(webApiRequest.Method);
                    var a = await client.ExecuteWebRequestAsync(
                    method: httpMethod,
                    queryString: webApiRequest.RequestUri, 
                    body: webApiRequest.Content, 
                    customHeaders: null,
                    contentType: null,
                    cancellationToken: token);
            });

and ran this.

I am not seeing the error in question and all functions as it should.

Could you help provide a repro for what you're doing? it may have something to do with the calls your making?
if you want to stand up a simple repro on a git hub repo, you can add me so I can have a look.

thanks

[Marvinnnne]

Your code works and when I replace my request POST/PATCH by a simple GET. It works.

So I thought errors was in my PATCH/POST request. But when I do a simple for each, I don't have error : "object not set an reference error". I just have 204 or some Bad Request/PreConditionFailed, functional error.

During all my tests with the Parallel ForEachAsync, sometimes I don't have "object not set an reference error" and sometimes I have it with the firsts requests directly.
But when I launch a first POST/PATCH request alone and then I call my ParallelForEach, it works every time.

Other point : This error "object not set an reference error" doesn't enter in my try/catch not like the Bad Request/PreConditionFailed error. I don't understand why.

I think it's linked with the service client which is not null, I guarantee it, but maybe there is some attribute in it null and that's why I have this error. And this attribute is initialized with a first request. I don't know, I'm totally lost with this behaviour.

[Marvinnnne]

Here the service client when I have this error

And here when I did a first request alone.

Does it means, it didn't have the time to initialize before the Parallel.ForEach ?