1 files changed, 10 insertions, 0 deletions

diff --git a/src/api/wix/WixToolset.Extensibility/Services/IFileSystem.cs b/src/api/wix/WixToolset.Extensibility/Services/IFileSystem.cs
index 26184462..cd987555 100644
--- a/src/api/wix/WixToolset.Extensibility/Services/IFileSystem.cs
+++ b/src/api/wix/WixToolset.Extensibility/Services/IFileSystem.cs
@@ -3,6 +3,7 @@
 namespace WixToolset.Extensibility.Services
 {
     using System;
+    using System.IO;
 
     /// <summary>
     /// Abstracts basic file system operations.
@@ -33,6 +34,15 @@ namespace WixToolset.Extensibility.Services
         void MoveFile(string source, string destination);
 
         /// <summary>
+        /// Opens a file.
+        /// </summary>
+        /// <param name="path">The file to open.</param>
+        /// <param name="mode">A System.IO.FileMode value that specifies whether a file is created if one does not exist, and determines whether the contents of existing files are retained or overwritten.</param>
+        /// <param name="access">A System.IO.FileAccess value that specifies the operations that can be performed on the file.</param>
+        /// <param name="share">A System.IO.FileShare value specifying the type of access other threads have to the file.</param>
+        FileStream OpenFile(string path, FileMode mode, FileAccess access, FileShare share);
+
+        /// <summary>
         /// Executes an action and retries on any exception a few times with short pause
         /// between each attempt. Primarily intended for use with file system operations
         /// that might get interrupted by external systems (usually anti-virus).