From 31775c94f0623532c47ad2f05da5a1685a172ac5 Mon Sep 17 00:00:00 2001
From: David Hall <dahall@byu.net>
Date: Sun, 3 Nov 2019 16:01:49 -0700
Subject: [PATCH] Fixed CallMethodWithTypedBuf to only set value on success.

---
 PInvoke/Shared/FunctionHelper.cs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/PInvoke/Shared/FunctionHelper.cs b/PInvoke/Shared/FunctionHelper.cs
index 2a7fdc2b..64f3c34e 100644
--- a/PInvoke/Shared/FunctionHelper.cs
+++ b/PInvoke/Shared/FunctionHelper.cs
@@ -112,13 +112,15 @@ namespace Vanara.PInvoke
 			if (err.Failed && (bufErr == null || bufErr.Value != err) && !buffErrs.Contains(err)) return err;
 			using (var buf = new SafeHGlobalHandle(sz.ToInt32(null)))
 			{
-				var ret = method(buf.DangerousGetHandle(), ref sz);
-				result = (outConverter ?? Conv)(buf.DangerousGetHandle(), sz);
-				return ret;
+				err = method(buf.DangerousGetHandle(), ref sz);
+				if (err.Succeeded)
+					result = (outConverter ?? Conv)(buf.DangerousGetHandle(), sz);
+				return err;
 			}
 
 			Win32Error GetSize(ref TSize sz1) => method(IntPtr.Zero, ref sz1);
-			TOut Conv(IntPtr p, TSize s) => p.ToStructure<TOut>();
+
+			static TOut Conv(IntPtr p, TSize s) => p == IntPtr.Zero ? default : p.Convert<TOut>(Convert.ToUInt32(s));
 		}
 
 		/// <summary>Calls a method with buffer for a type and gets the result or error.</summary>