Fixed NullReferenceException in OpenXmlElement RawOuterXml field

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ## Version 2.12.1
 
 ### Fixed
+- Fixed `OpenXmlElement.RawOuterXml` to properly set null values without throwing (#818)
 - Allow rewriting of all malformed URIs regardless of target value (#835)
 
 ## Version 2.12.0 - 2020-12-09

src/DocumentFormat.OpenXml/OpenXmlElement.cs

@@ -154,15 +154,7 @@ internal string RawOuterXml
         {
             get => _rawOuterXml;
 
-            set
-            {
-                if (string.IsNullOrEmpty(value))
-                {
-                    _rawOuterXml = string.Empty;
-                }
-
-                _rawOuterXml = value;
-            }
+            set => _rawOuterXml = value ?? string.Empty;
         }
 
         private Framework.Metadata.ElementState _state;

test/DocumentFormat.OpenXml.Tests/ofapiTest/OpenXmlElementTest2.cs

@@ -142,5 +142,41 @@ public void TestGetXPathIndex()
             target = unknown2.GetXPathIndex();
             Assert.Equal(2, target);
         }
+
+        /// <summary>
+        /// Tests if empty string is set when
+        /// null value is given to setter
+        /// </summary>
+        [Fact]
+        public void TestSetRawOuterXmlField_NullValueIsSet_FieldShouldNotBeNull()
+        {
+            var openXmlElement = new Document();
+            openXmlElement.RawOuterXml = null;
+            Assert.NotNull(openXmlElement.RawOuterXml);
+        }
+
+        /// <summary>
+        /// Tests if proper string value is set when
+        /// setter is invoked
+        /// </summary>
+        [Fact]
+        public void TestSetRawOuterXmlField_ValueIsSet_FieldShouldContainSetValue()
+        {
+            var openXmlElement = new Document();
+            var testValue = "Some proper value";
+            openXmlElement.RawOuterXml = testValue;
+            Assert.Equal(testValue, openXmlElement.RawOuterXml);
+        }
+
+        /// <summary>
+        /// Tests if field is empty when empty string is set
+        /// </summary>
+        [Fact]
+        public void TestSetRawOuterXmlField_SetValueIsEmpty_FieldShouldBeEmpty()
+        {
+            var openXmlElement = new Document();
+            openXmlElement.RawOuterXml = string.Empty;
+            Assert.Equal(string.Empty, openXmlElement.RawOuterXml);
+        }
     }
 }