Properly collapse the right range when encountering nested #if regions.

src/EditorFeatures/CSharpTest/Structure/DisabledTextStructureTests.cs

@@ -111,6 +111,77 @@ class P {
     {
 #if Bar
        M();
+#endif
+        }|}
+#endif
+    }
+";
+
+            await VerifyBlockSpansAsync(code,
+                Region("span", CSharpStructureHelpers.Ellipsis, autoCollapse: true));
+        }
+
+        [WorkItem(459257, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=459257")]
+        [Fact, Trait(Traits.Feature, Traits.Features.Outlining)]
+        public async Task NestedDisabledCodePreProcessorDirectivesWithElseShouldCollapseEntireDisabledRegion()
+        {
+            const string code = @"
+class P {
+#if Goo
+{|span:    void $$M()
+    {
+#if Bar
+       M();
+#else
+
+#endif
+        }|}
+#endif
+    }
+";
+
+            await VerifyBlockSpansAsync(code,
+                Region("span", CSharpStructureHelpers.Ellipsis, autoCollapse: true));
+        }
+
+        [WorkItem(459257, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=459257")]
+        [Fact, Trait(Traits.Feature, Traits.Features.Outlining)]
+        public async Task NestedDisabledCodePreProcessorDirectivesWithElifShouldCollapseEntireDisabledRegion()
+        {
+            const string code = @"
+class P {
+#if Goo
+{|span:    void $$M()
+    {
+#if Bar
+       M();
+#elif Baz
+
+#endif
+        }|}
+#endif
+    }
+";
+
+            await VerifyBlockSpansAsync(code,
+                Region("span", CSharpStructureHelpers.Ellipsis, autoCollapse: true));
+        }
+
+        [WorkItem(459257, "https://devdiv.visualstudio.com/DevDiv/_workitems?id=459257")]
+        [Fact, Trait(Traits.Feature, Traits.Features.Outlining)]
+        public async Task NestedDisabledCodePreProcessorDirectivesWithElseAndElifShouldCollapseEntireDisabledRegion()
+        {
+            const string code = @"
+class P {
+#if Goo
+{|span:    void $$M()
+    {
+#if Bar
+       M();
+#else
+
+#elif Baz
+
 #endif
         }|}
 #endif

src/Features/CSharp/Portable/Structure/Providers/DisabledTextTriviaStructureProvider.cs

@@ -59,18 +59,24 @@ internal class DisabledTextTriviaStructureProvider : AbstractSyntaxTriviaStructu
             var nestedIfDirectiveTrivia = 0;
             for (var i = indexInParent; i < parentTriviaList.Count; i++)
             {
-                if (parentTriviaList[i].IsKind(SyntaxKind.IfDirectiveTrivia))
+                var currentTrivia = parentTriviaList[i];
+                if (currentTrivia.IsKind(SyntaxKind.IfDirectiveTrivia))
                 {
                     nestedIfDirectiveTrivia++;
+                    continue;
                 }
 
-                if (parentTriviaList[i].IsKind(SyntaxKind.EndIfDirectiveTrivia) ||
-                    parentTriviaList[i].IsKind(SyntaxKind.ElifDirectiveTrivia) ||
-                    parentTriviaList[i].IsKind(SyntaxKind.ElseDirectiveTrivia))
+                var isEndIf = currentTrivia.IsKind(SyntaxKind.EndIfDirectiveTrivia);
+                if (isEndIf ||
+                    currentTrivia.IsKind(SyntaxKind.ElifDirectiveTrivia) ||
+                    currentTrivia.IsKind(SyntaxKind.ElseDirectiveTrivia))
                 {
                     if (nestedIfDirectiveTrivia > 0)
                     {
-                        nestedIfDirectiveTrivia--;
+                        if (isEndIf)
+                        {
+                            nestedIfDirectiveTrivia--;
+                        }
                     }
                     else
                     {