[InMemoryExporter] Throw ObjectDisposedException if Export happened after disposal

src/OpenTelemetry.Exporter.InMemory/.publicApi/net462/PublicAPI.Unshipped.txt

@@ -0,0 +1 @@
+override OpenTelemetry.Exporter.InMemoryExporter<T>.Dispose(bool disposing) -> void

src/OpenTelemetry.Exporter.InMemory/.publicApi/netstandard2.0/PublicAPI.Unshipped.txt

@@ -0,0 +1 @@
+override OpenTelemetry.Exporter.InMemoryExporter<T>.Dispose(bool disposing) -> void

src/OpenTelemetry.Exporter.InMemory/CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+* Changed error handling, `InMemoryExporter` will now throw
+  `ObjectDisposedException` if `Export` is invoked after the exporter is
+  disposed.
+  ([#3607](https://github.com/open-telemetry/opentelemetry-dotnet/issues/3607))
+
 ## 1.4.0-alpha.2
 
 Released 2022-Aug-18

src/OpenTelemetry.Exporter.InMemory/InMemoryExporter.cs

@@ -14,6 +14,7 @@
 // limitations under the License.
 // </copyright>
 
+using System;
 using System.Collections.Generic;
 
 namespace OpenTelemetry.Exporter
@@ -23,6 +24,7 @@ public class InMemoryExporter<T> : BaseExporter<T>
     {
         private readonly ICollection<T> exportedItems;
         private readonly ExportFunc onExport;
+        private bool disposed;
 
         public InMemoryExporter(ICollection<T> exportedItems)
         {
@@ -37,7 +39,27 @@ internal InMemoryExporter(ExportFunc exportFunc)
 
         internal delegate ExportResult ExportFunc(in Batch<T> batch);
 
-        public override ExportResult Export(in Batch<T> batch) => this.onExport(batch);
+        public override ExportResult Export(in Batch<T> batch)
+        {
+            if (this.disposed)
+            {
+                // Since in-memory exporter is designed for testing purpose, having an early error would help developers to catch the bug during early stage of the development.
+                throw new ObjectDisposedException(this.GetType().Name, "The in-memory exporter is still being invoked after it is disposed. This indicates a wrong use of the OpenTelemetry .NET SDK, where the object lifecycle is not properly managed.");
+            }
+
+            return this.onExport(batch);
+        }
+
+        /// <inheritdoc/>
+        protected override void Dispose(bool disposing)
+        {
+            if (!this.disposed)
+            {
+                this.disposed = true;
+            }
+
+            base.Dispose(disposing);
+        }
 
         private ExportResult DefaultExport(in Batch<T> batch)
         {

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/PrometheusExporter.cs

@@ -28,7 +28,7 @@ internal sealed class PrometheusExporter : BaseExporter<Metric>, IPullMetricExpo
     {
         private Func<int, bool> funcCollect;
         private Func<Batch<Metric>, ExportResult> funcExport;
-        private bool disposed = false;
+        private bool disposed;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PrometheusExporter"/> class.