{"record":{"id":"2d9cacf0cd6d9b54","repo":"dotnet/reactive","slug":"value-cannot-be-null-parameter-scheduler-scheduleddisposable","errorCode":null,"errorMessage":"Value cannot be null. (Parameter 'scheduler')","messagePattern":"Value cannot be null\\. \\(Parameter 'scheduler'\\)","errorType":"validation","errorClass":"ArgumentNullException","httpStatus":null,"severity":"error","filePath":"Rx.NET/Source/src/System.Reactive/Disposables/ScheduledDisposable.cs","lineNumber":24,"sourceCode":"\nnamespace System.Reactive.Disposables\n{\n    /// <summary>\n    /// Represents a disposable resource whose disposal invocation will be scheduled on the specified <seealso cref=\"IScheduler\"/>.\n    /// </summary>\n    public sealed class ScheduledDisposable : ICancelable\n    {\n        private SingleAssignmentDisposableValue _disposable;\n\n        /// <summary>\n        /// Initializes a new instance of the <see cref=\"ScheduledDisposable\"/> class that uses an <see cref=\"IScheduler\"/> on which to dispose the disposable.\n        /// </summary>\n        /// <param name=\"scheduler\">Scheduler where the disposable resource will be disposed on.</param>\n        /// <param name=\"disposable\">Disposable resource to dispose on the given scheduler.</param>\n        /// <exception cref=\"ArgumentNullException\"><paramref name=\"scheduler\"/> or <paramref name=\"disposable\"/> is null.</exception>\n        public ScheduledDisposable(IScheduler scheduler, IDisposable disposable)\n        {\n            Scheduler = scheduler ?? throw new ArgumentNullException(nameof(scheduler));\n            _disposable.Disposable = disposable ?? throw new ArgumentNullException(nameof(disposable));\n        }\n\n        /// <summary>\n        /// Gets the scheduler where the disposable resource will be disposed on.\n        /// </summary>\n        public IScheduler Scheduler { get; }\n\n        /// <summary>\n        /// Gets the underlying disposable. After disposal, the result is undefined.\n        /// </summary>\n        public IDisposable Disposable => _disposable.Disposable ?? Disposables.Disposable.Empty;\n\n        /// <summary>\n        /// Gets a value that indicates whether the object is disposed.\n        /// </summary>\n        public bool IsDisposed => _disposable.IsDisposed;\n","sourceCodeStart":6,"sourceCodeEnd":42,"githubUrl":"https://github.com/dotnet/reactive/blob/94b5d5ab912789f5abe9a72138a25bbd716fe59c/Rx.NET/Source/src/System.Reactive/Disposables/ScheduledDisposable.cs#L6-L42","documentation":"ScheduledDisposable's constructor requires a non-null IScheduler on which the wrapped resource will be disposed; null is rejected with ArgumentNullException. The scheduler is stored in a get-only property and is essential for DisposeAsync/Dispose routing.","triggerScenarios":"Calling new ScheduledDisposable(null, someDisposable) — passing null for the 'scheduler' parameter, e.g. when a scheduler variable or DI-resolved IScheduler is null.","commonSituations":"DI container that failed to register IScheduler, configuration where the scheduler is chosen conditionally and both branches yield null, or testing code with a stubbed scheduler left unassigned.","solutions":["Pass an actual scheduler instance, e.g. Scheduler.Default or Scheduler.Immediate.","Resolve/register IScheduler in your DI container before constructing the ScheduledDisposable.","Fall back to Scheduler.Immediate when no scheduler is configured and immediate disposal is acceptable."],"exampleFix":"// before\nvar sd = new ScheduledDisposable(configuredScheduler, resource); // configuredScheduler is null\n// after\nvar sd = new ScheduledDisposable(configuredScheduler ?? Scheduler.Default, resource);","handlingStrategy":"validation","validationCode":"if (scheduler is null) scheduler = Scheduler.Default;\nvar sd = new ScheduledDisposable(scheduler, resource);","typeGuard":"static bool HasScheduler(IScheduler s) => s is not null;","tryCatchPattern":"try { var sd = new ScheduledDisposable(scheduler, resource); }\ncatch (ArgumentNullException ex) when (ex.ParamName == \"scheduler\") { /* use Scheduler.Default fallback */ }","preventionTips":["Register IScheduler in DI and verify resolution at startup.","Default to Scheduler.Default/Immediate at composition edges instead of null.","Enable nullable reference types to catch unassigned scheduler variables at compile time."],"tags":["null-argument","scheduler","system-reactive","argument-validation"],"backgroundTag":"null-argument","analyzedSha":"94b5d5ab912789f5abe9a72138a25bbd716fe59c","analyzedAt":"2026-09-15T02:26:24.759Z","contentChangedAt":"2026-09-15T02:26:24.759Z","schemaVersion":2},"datasetVersion":"2026-09-15T23:17:13.987Z"}