new file, new implementation with separate thread to modify the colle…

src/Blazor.Diagrams/Components/Controls/ControlsLayerRenderer.razor

@@ -1,4 +1,4 @@
-@foreach (var model in BlazorDiagram.Controls.Models)
+@foreach (var model in BlazorDiagram.Controls.Models.ToList())
 {
     var controls = BlazorDiagram.Controls.GetFor(model)!;
     if (!controls.Visible || controls.Count == 0)

tests/Blazor.Diagrams.Tests/Components/ControlsLayerRendererTests.cs

@@ -0,0 +1,95 @@
+using Bunit;
+using Xunit;
+using Blazor.Diagrams.Components.Controls;
+using Blazor.Diagrams.Core.Models.Base;
+
+namespace Blazor.Diagrams.Tests.Components
+{
+    public class ControlsLayerRendererTests
+    {
+        [Fact]
+        public async Task Rendering_WithChangingModels_ShouldNotThrowException()
+        {
+            // Arrange
+            using var ctx = new TestContext();
+            var diagram = new BlazorDiagram();
+
+            var model1 = new CustomModel();
+            var model2 = new CustomModel();
+
+            diagram.Controls.AddFor(model1);
+            diagram.Controls.AddFor(model2);
+
+            var renderStarted = new ManualResetEventSlim(false);
+            var modificationStarted = new ManualResetEventSlim(false);
+            var exceptionThrown = false;
+
+            IRenderedComponent<ControlsLayerRenderer>? cut = null;
+
+            // Task to render the component
+            var renderTask = Task.Run(async () =>
+            {
+                try
+                {
+                    cut = ctx.RenderComponent<ControlsLayerRenderer>(parameters => parameters
+                        .Add(c => c.BlazorDiagram, diagram));
+
+                    renderStarted.Set(); // Indicate that rendering has started
+
+                    // Force Blazor to update while modifications happen
+                    for (int i = 0; i < 10; i++)
+                    {
+                        await cut.InvokeAsync(() =>
+                        {
+                            cut.Render();
+                        });
+                        Thread.Sleep(5); // Let it process
+                    }
+
+                    modificationStarted.Wait(); // Wait for modifications
+                }
+                catch (InvalidOperationException)
+                {
+                    exceptionThrown = true;
+                }
+            });
+
+            // Wait to ensure rendering starts first
+            renderStarted.Wait();
+            await Task.Delay(10); // Allow time for rendering
+
+            // Task to modify the collection while rendering happens
+            var modifyTask = Task.Run(async () =>
+            {
+                try
+                {
+                    foreach (var model in diagram.Controls.Models)
+                    {
+                        if (model == model1)
+                        {
+                            await cut.InvokeAsync(() =>
+                            {
+                                diagram.Controls.RemoveFor(model1);
+                            });
+                        }
+                    }
+                }
+                catch (InvalidOperationException)
+                {
+                    exceptionThrown = true;
+                }
+                finally
+                {
+                    modificationStarted.Set();
+                }
+            });
+
+            // Wait for tasks to complete
+            await Task.WhenAll(renderTask, modifyTask);
+
+            // Assert
+            Assert.False(exceptionThrown, "Iteration should not throw an exception when using .ToList()");
+        }
+        private class CustomModel : Model { }
+    }
+}