Add OnBeforeClose hook.

src/Blazored.Modal/BlazoredModalInstance.razor.cs

@@ -94,6 +94,12 @@ public async Task CloseAsync()
     /// <param name="modalResult"></param>
     public async Task CloseAsync(ModalResult modalResult)
     {
+        //If we have a OnBeforeClose we try to invoke it here
+        if (Options.OnBeforeClose != null)
+        {
+            await Options.OnBeforeClose(modalResult);
+        }
+
         // Fade out the modal, and after that actually remove it
         if (AnimationType is ModalAnimationType.FadeInOut)
         {

src/Blazored.Modal/Configuration/ModalOptions.cs

@@ -1,4 +1,6 @@
-namespace Blazored.Modal;
+using Blazored.Modal.Services;
+
+namespace Blazored.Modal;
 
 public class ModalOptions
 {
@@ -14,4 +16,6 @@ public class ModalOptions
     public ModalAnimationType? AnimationType { get; set; }
     public bool? UseCustomLayout { get; set; }
     public bool? ActivateFocusTrap { get; set; }
+
+    public Func<ModalResult,Task>? OnBeforeClose { get; set; }
 }

tests/Blazored.Modal.Tests/ModalOptionsTests.cs

@@ -1,4 +1,5 @@
-using Blazored.Modal.Services;
+using System.Threading.Tasks;
+using Blazored.Modal.Services;
 using Blazored.Modal.Tests.Assets;
 using Bunit;
 using Microsoft.AspNetCore.Components;
@@ -266,5 +267,29 @@ public void ModalDisplaysCustomSizeClassWhenSizeIsCustom()
             // Assert
             Assert.NotNull(cut.Find(".my-custom-size"));
         }
+
+        [Fact]
+        public void ModalTriggersOnBeforeCloseWhenModalCloses()
+        {
+            // Arrange
+            var onBeforeCloseTriggered = false;
+            var options = new ModalOptions
+            {
+                OnBeforeClose = result =>
+                {
+                    onBeforeCloseTriggered = result != null; 
+                    return Task.CompletedTask;
+                }
+            };
+            var modalService = Services.GetService<IModalService>();
+            var cut = RenderComponent<BlazoredModal>(CascadingValue(modalService!));
+
+            // Act
+            modalService.Show<TestComponent>("", options);
+            cut.Find(".bm-close").Click();
+
+            // Assert
+            Assert.True(onBeforeCloseTriggered);
+        }
     }
 }