From 3c476a49ee8e191bec31e89bd39edde4a5837fb3 Mon Sep 17 00:00:00 2001
From: Joshua Marner <biz@jmarner.com>
Date: Tue, 1 Oct 2024 15:48:56 -0500
Subject: [PATCH 1/3] Add test specifying feature

---
 src/Elmish.WPF.Tests/DynamicViewModelTests.fs | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/Elmish.WPF.Tests/DynamicViewModelTests.fs b/src/Elmish.WPF.Tests/DynamicViewModelTests.fs
index baaa5bff..e54888af 100644
--- a/src/Elmish.WPF.Tests/DynamicViewModelTests.fs
+++ b/src/Elmish.WPF.Tests/DynamicViewModelTests.fs
@@ -844,6 +844,26 @@ module TwoWayValidate =
     }
 
 
+  [<Fact>]
+  let ``when model is updated, should trigger NotifyPropertyChanged on HasErrors iff the value returned by validate changes`` () =
+    Property.check <| property {
+      let! name = GenX.auto<string>
+      let! m1 = GenX.auto<int>
+      let! m2 = GenX.auto<int>
+
+      let get _ = ()
+      let set _ _ = ()
+      let validate m = if m < 0 then ValueSome (string m) else ValueNone
+
+      let binding = twoWayValidate name get set validate
+      let vm = TestVm(m1, binding)
+
+      vm.UpdateModel m2
+
+      test <@ vm.NumPcTriggersFor "HasErrors" = if (validate m1 |> ValueOption.isNone) = (validate m2 |> ValueOption.isNone) then 0 else 1 @>
+    }
+
+
   [<Fact>]
   let ``when validate returns ValueNone, HasErrors should return false and GetErrors should return an empty collection`` () =
     Property.check <| property {

From 7f6b5b7c2d8a218adcab7981653634a168ab188c Mon Sep 17 00:00:00 2001
From: Joshua Marner <biz@jmarner.com>
Date: Tue, 1 Oct 2024 15:49:18 -0500
Subject: [PATCH 2/3] Notify HasErrors property when it changes

---
 src/Elmish.WPF/ViewModels.fs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/Elmish.WPF/ViewModels.fs b/src/Elmish.WPF/ViewModels.fs
index e881e6b8..e58c8f8a 100644
--- a/src/Elmish.WPF/ViewModels.fs
+++ b/src/Elmish.WPF/ViewModels.fs
@@ -177,8 +177,10 @@ type [<AllowNullLiteral>] internal DynamicViewModel<'model, 'msg>
     member _.CurrentModel : 'model = helper.Model
 
     member _.UpdateModel (newModel: 'model) : unit =
+      let prevHasErrors = (helper :> INotifyDataErrorInfo).HasErrors
       let eventsToRaise = ViewModelHelper.getEventsToRaise newModel helper
       helper <- { helper with Model = newModel }
+      let eventsToRaise = if prevHasErrors = (helper :> INotifyDataErrorInfo).HasErrors then eventsToRaise else (PropertyChanged "HasErrors") :: eventsToRaise
       ViewModelHelper.raiseEvents eventsToRaise helper
 
   override _.TryGetMember (binder, result) =

From bf0c2bac4ccbd65113fdf82707e5b2d900675366 Mon Sep 17 00:00:00 2001
From: Joshua Marner <biz@jmarner.com>
Date: Tue, 1 Oct 2024 15:59:52 -0500
Subject: [PATCH 3/3] Bump version

---
 RELEASE_NOTES.md                 | 3 +++
 src/Elmish.WPF/Elmish.WPF.fsproj | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 30f1031b..aa03d24d 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,3 +1,6 @@
+#### 4.0.0-beta-56
+* Add NotifyPropertyChanged for the HasErrors property.
+
 #### 4.0.0-beta-55
 * Add TwoWayT bindings for workflows that reuse bindings.
 * Add OneWayToSeqT bindings.
diff --git a/src/Elmish.WPF/Elmish.WPF.fsproj b/src/Elmish.WPF/Elmish.WPF.fsproj
index 371935dc..a9053e38 100644
--- a/src/Elmish.WPF/Elmish.WPF.fsproj
+++ b/src/Elmish.WPF/Elmish.WPF.fsproj
@@ -18,7 +18,7 @@
     <PackageProjectUrl>https://github.com/elmish/Elmish.WPF</PackageProjectUrl>
     <PackageTags>WPF F# fsharp Elmish Elm</PackageTags>
     <PackageIcon>elmish-wpf-logo-128x128.png</PackageIcon>
-    <Version>4.0.0-beta-55</Version>
+    <Version>4.0.0-beta-56</Version>
     <PackageReleaseNotes>https://github.com/elmish/Elmish.WPF/blob/master/RELEASE_NOTES.md</PackageReleaseNotes>
     <PackageReadmeFile>README.md</PackageReadmeFile>
     <!--Turn on warnings for unused values (arguments and let bindings) -->