4 files changed, 64 insertions, 0 deletions

diff --git a/src/api/burn/WixToolset.Mba.Core/BootstrapperApplication.cs b/src/api/burn/WixToolset.Mba.Core/BootstrapperApplication.cs
index fd36cf26..8a2e0e93 100644
--- a/src/api/burn/WixToolset.Mba.Core/BootstrapperApplication.cs
+++ b/src/api/burn/WixToolset.Mba.Core/BootstrapperApplication.cs
@@ -209,6 +209,9 @@ namespace WixToolset.Mba.Core
         public event EventHandler<ApplyCompleteEventArgs> ApplyComplete;
 
         /// <inheritdoc/>
+        public event EventHandler<ApplyDowngradeEventArgs> ApplyDowngrade;
+
+        /// <inheritdoc/>
         public event EventHandler<ExecuteProgressEventArgs> ExecuteProgress;
 
         /// <inheritdoc/>
@@ -1056,6 +1059,19 @@ namespace WixToolset.Mba.Core
         }
 
         /// <summary>
+        /// Called by the engine, raises the <see cref="ApplyDowngrade"/> event.
+        /// </summary>
+        /// <param name="args">Additional arguments for this event.</param>
+        protected virtual void OnApplyDowngrade(ApplyDowngradeEventArgs args)
+        {
+            EventHandler<ApplyDowngradeEventArgs> handler = this.ApplyDowngrade;
+            if (null != handler)
+            {
+                handler(this, args);
+            }
+        }
+
+        /// <summary>
         /// Called by the engine, raises the <see cref="ExecuteProgress"/> event.
         /// </summary>
         /// <param name="args">Additional arguments for this event.</param>
@@ -1907,6 +1923,15 @@ namespace WixToolset.Mba.Core
             return args.HResult;
         }
 
+        int IBootstrapperApplication.OnApplyDowngrade(int hrRecommendation, ref int hrStatus)
+        {
+            ApplyDowngradeEventArgs args = new ApplyDowngradeEventArgs(hrRecommendation, hrStatus);
+            this.OnApplyDowngrade(args);
+
+            hrStatus = args.Status;
+            return args.HResult;
+        }
+
         int IBootstrapperApplication.OnLaunchApprovedExeBegin(ref bool fCancel)
         {
             LaunchApprovedExeBeginEventArgs args = new LaunchApprovedExeBeginEventArgs(fCancel);
diff --git a/src/api/burn/WixToolset.Mba.Core/EventArgs.cs b/src/api/burn/WixToolset.Mba.Core/EventArgs.cs
index d8ec7998..c93c2885 100644
--- a/src/api/burn/WixToolset.Mba.Core/EventArgs.cs
+++ b/src/api/burn/WixToolset.Mba.Core/EventArgs.cs
@@ -1859,6 +1859,30 @@ namespace WixToolset.Mba.Core
     }
 
     /// <summary>
+    /// Event arguments for <see cref="IDefaultBootstrapperApplication.ApplyDowngrade"/>
+    /// </summary>
+    [Serializable]
+    public class ApplyDowngradeEventArgs : HResultEventArgs
+    {
+        /// <summary />
+        public ApplyDowngradeEventArgs(int hrRecommendation, int hrStatus)
+        {
+            this.Recommendation = hrRecommendation;
+            this.Status = hrStatus;
+        }
+
+        /// <summary>
+        /// Gets the recommended HRESULT.
+        /// </summary>
+        public int Recommendation { get; private set; }
+
+        /// <summary>
+        /// Gets or sets the HRESULT for Apply.
+        /// </summary>
+        public int Status { get; set; }
+    }
+
+    /// <summary>
     /// EventArgs for <see cref="IDefaultBootstrapperApplication.CacheAcquireResolving"/>.
     /// </summary>
     [Serializable]
diff --git a/src/api/burn/WixToolset.Mba.Core/IBootstrapperApplication.cs b/src/api/burn/WixToolset.Mba.Core/IBootstrapperApplication.cs
index 4ab0f8d9..d4fe8320 100644
--- a/src/api/burn/WixToolset.Mba.Core/IBootstrapperApplication.cs
+++ b/src/api/burn/WixToolset.Mba.Core/IBootstrapperApplication.cs
@@ -1160,6 +1160,16 @@ namespace WixToolset.Mba.Core
             [MarshalAs(UnmanagedType.U4)] ref RelatedBundlePlanType pRequestedType,
             [MarshalAs(UnmanagedType.Bool)] ref bool fCancel
             );
+
+        /// <summary>
+        /// See <see cref="IDefaultBootstrapperApplication.ApplyDowngrade"/>.
+        /// </summary>
+        [PreserveSig]
+        [return: MarshalAs(UnmanagedType.I4)]
+        int OnApplyDowngrade(
+            [MarshalAs(UnmanagedType.I4)] int hrRecommended,
+            [MarshalAs(UnmanagedType.I4)] ref int hrStatus
+            );
     }
 
     /// <summary>
diff --git a/src/api/burn/WixToolset.Mba.Core/IDefaultBootstrapperApplication.cs b/src/api/burn/WixToolset.Mba.Core/IDefaultBootstrapperApplication.cs
index ebd1580b..c9284b69 100644
--- a/src/api/burn/WixToolset.Mba.Core/IDefaultBootstrapperApplication.cs
+++ b/src/api/burn/WixToolset.Mba.Core/IDefaultBootstrapperApplication.cs
@@ -20,6 +20,11 @@ namespace WixToolset.Mba.Core
         event EventHandler<ApplyCompleteEventArgs> ApplyComplete;
 
         /// <summary>
+        /// Fired when the plan determined that nothing should happen to prevent downgrading.
+        /// </summary>
+        event EventHandler<ApplyDowngradeEventArgs> ApplyDowngrade;
+
+        /// <summary>
         /// Fired when the engine is about to begin an MSI transaction.
         /// </summary>
         event EventHandler<BeginMsiTransactionBeginEventArgs> BeginMsiTransactionBegin;