diff --git a/BuildAll.ps1 b/BuildAll.ps1
old mode 100644
new mode 100755
diff --git a/dev/UndockedRegFreeWinRT/UndockedRegFreeWinRT-AutoInitializer.cs b/dev/UndockedRegFreeWinRT/UndockedRegFreeWinRT-AutoInitializer.cs
index 2e07c542..70d0c100 100644
--- a/dev/UndockedRegFreeWinRT/UndockedRegFreeWinRT-AutoInitializer.cs
+++ b/dev/UndockedRegFreeWinRT/UndockedRegFreeWinRT-AutoInitializer.cs
@@ -16,6 +16,11 @@ internal static class NativeMethods
     {
         [DllImport("Microsoft.WindowsAppRuntime.dll", CharSet = CharSet.Unicode, ExactSpelling = true)]
         internal static extern int WindowsAppRuntime_EnsureIsLoaded();
+        
+        // Direct Win32 API call to set environment variable as fallback
+        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        internal static extern bool SetEnvironmentVariableW(string name, string value);
     }
 
     class AutoInitialize
@@ -24,7 +29,37 @@ class AutoInitialize
         internal static void AccessWindowsAppSDK()
         {
             // Set base directory env var for PublishSingleFile support (referenced by SxS redirection)
-            Environment.SetEnvironmentVariable("MICROSOFT_WINDOWSAPPRUNTIME_BASE_DIRECTORY", AppContext.BaseDirectory);
+            try
+            {
+                Environment.SetEnvironmentVariable("MICROSOFT_WINDOWSAPPRUNTIME_BASE_DIRECTORY", AppContext.BaseDirectory);
+            }
+            catch (System.MissingMethodException)
+            {
+                // Fallback: Use direct Win32 API call when Environment.SetEnvironmentVariable is not available
+                // This can happen in trimmed environments (PublishTrimmed=true)
+                try
+                {
+                    NativeMethods.SetEnvironmentVariableW("MICROSOFT_WINDOWSAPPRUNTIME_BASE_DIRECTORY", AppContext.BaseDirectory);
+                }
+                catch
+                {
+                    // Ignore failures in the fallback path - continue execution
+                    // as it's better than crashing the application
+                }
+            }
+            catch (System.Exception)
+            {
+                // Catch any other unexpected exceptions to ensure application doesn't crash
+                // Try the fallback mechanism
+                try
+                {
+                    NativeMethods.SetEnvironmentVariableW("MICROSOFT_WINDOWSAPPRUNTIME_BASE_DIRECTORY", AppContext.BaseDirectory);
+                }
+                catch
+                {
+                    // Ignore failures in the fallback path
+                }
+            }
 
             // No error handling needed as the target function does nothing (just {return S_OK}).
             // It's the act of calling the function causing the DllImport to load the DLL that