在IIS上托管时拆分字符串会引发InvalidOperationException

Question

I wrote the following code:

private string makeMailContents(Klant klant, Mail mail)
{
    var builder = new BodyBuilder();
    var path = Path.Combine("wwwroot/trackers/track_open.png");
    var img = builder.LinkedResources.Add(path);
    byte[] data = Convert.FromBase64String(mail.Content);
    string decoded = Encoding.UTF8.GetString(data);
    string code;
    string final = "";
    Regex regex = new Regex(@"\[([^]]*)\]");

    img.ContentId = MimeUtils.GenerateMessageId();

    var splitContent = decoded.Split(' ');

    foreach(string word in splitContent) // this is line 265
    { 
            if (word.Contains('[') && word.Contains(']'))
            {
                try
                {
                    code = Regex.Match(word, @"\[([^]]*)\]").Groups[1].Value.ToLower();
                    switch (code)
                    {
                        case "voornaam":
                            final += regex.Replace(word, klant.vnaam) + ' ';
                            break;
                        case "achternaam":
                            final += regex.Replace(word, klant.anaam) + ' ';
                            break;
                        case "naam":
                            final += regex.Replace(word, klant.vnaam + ' ' + klant.anaam + ' ');
                            break;
                        case "onderwerp":
                            final += regex.Replace(word, mail.Onderwerp + ' ');
                            break;
                        case "datum":
                            final += regex.Replace(word, DateTime.Now.ToString("dd-MM-yyyy") + ' ');
                            break;
                    }
                }
                catch (Exception ex)
                {
                    final += ex;
                }
            }
            else
            {
                final += word + ' ';
            }
    }
}

Whenever I run this code on my local machine and my test server it executes the code like it should without any exceptions.

But whenever I host this on my current live server it throws the following exception:

InvalidOperationException: Sequence contains no elements

And this exceptions keeps pointing towards the splitContent and it tells me that it doesn't contain elements. And yes, the mail.Content is filled with a valid base64 string, I checked both with fiddler and postman.

Does anyone have the slightest clue of what's going on here? I'm also not sure if it's the IIS settings or somehow my code. I normally have a colleague who manages the IIS but he is on vacation right now. Can someone help me out with this?

This is the data the mail receives when called:

 {      
    "Onderwerp":"Dit is een test campagne",
    "afzender":1,
    "campagne":1,
    "Content":"PHA+RGl0IGlzIGVlbiB0ZXN0IG1hYXQ8L3A+Cg==",
    "docs":"['kamer2.jpg']",
    "template":null,
    "verzenddat":"8/17/18, 3:55 PM"
}

full exception:

System.InvalidOperationException: Sequence contains no elements
   at System.Linq.Enumerable.Last[TSource](IEnumerable`1 source)
   at lambda_method(Closure , QueryContext )
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass17_1`1.<CompileQueryCore>b__0(QueryContext qc)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at System.Linq.Queryable.Last[TSource](IQueryable`1 source)
   at MailerAPI.Mailer.Sender.makeMailContents(Klant klant, Mail mail) in C:\Users\Hofkey\Source\Repos\MailerAPI\MailerAPI\Mailer\Sender.cs:line 265
   at System.Dynamic.UpdateDelegates.UpdateAndExecute3[T0,T1,T2,TRet](CallSite site, T0 arg0, T1 arg1, T2 arg2)
   at MailerAPI.Mailer.Sender.<sendMessage>d__7.MoveNext() in C:\Users\Hofkey\Source\Repos\MailerAPI\MailerAPI\Mailer\Sender.cs:line 161
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at MailerAPI.Controllers.MailController.<Post>d__13.MoveNext() in C:\Users\Hofkey\Source\Repos\MailerAPI\MailerAPI\Controllers\MailController.cs:line 96
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeActionMethodAsync>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeNextActionFilterAsync>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.<InvokeInnerFilterAsync>d__14.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.<InvokeNextResourceFilter>d__22.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.<InvokeFilterPipelineAsync>d__17.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.<InvokeAsync>d__15.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Builder.RouterMiddleware.<Invoke>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Cors.Infrastructure.CorsMiddleware.<Invoke>d__7.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.<Invoke>d__7.MoveNext()

The exception also gets thrown when I replace the model properties with just a plain string.

UPDATE Whenever I run this code in my values controller to test the decoded.split(' ') it actually works. When I return the decoded.split(' ') I actually get an array of strings.

So now I know that the problem only occurs within the method, which is located in a Sender class and being called in the MailerController, and it also only occurs in the current server.

Answer 1

You appear to be making a call to .Last() at or through the code located at C:\\Users\\Hofkey\\Source\\Repos\\MailerAPI\\MailerAPI\\Mailer\\Sender.cs:line 265 .

The Linq extension method .Last() demands that there is at least one item that it can grab. To work around this requirement, you have various options:

• use .LastOrDefault() accompanied with appropriate null handling, or
• before using .Last() , first check with if (... .Any()) if it is OK to call .Last() .

For further reference, see LINQ Element Operations