TiledMap property multi-line bug fix (#641)

Source/Demos/Tutorials/Content/TiledMaps/level01.tmx

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<map version="1.0" tiledversion="1.1.6" orientation="orthogonal" renderorder="right-down" width="40" height="10" tilewidth="128" tileheight="128" infinite="0" backgroundcolor="#7d7d7d" nextobjectid="23">
+<map version="1.2" tiledversion="1.2.4" orientation="orthogonal" renderorder="right-down" width="40" height="10" tilewidth="128" tileheight="128" infinite="0" backgroundcolor="#7d7d7d" nextlayerid="10" nextobjectid="23">
  <properties>
   <property name="awesome" value="42"/>
  </properties>
@@ -31,16 +31,16 @@
    </properties>
   </tile>
  </tileset>
- <imagelayer name="Background 1">
+ <imagelayer id="1" name="Background 1">
   <image source="hills.png" trans="000000" width="2048" height="1536"/>
  </imagelayer>
- <group name="Ground Group">
-  <layer name="Water" width="40" height="10">
+ <group id="2" name="Ground Group">
+  <layer id="3" name="Water" width="40" height="10">
    <data encoding="base64" compression="gzip">
    H4sIAAAAAAAACmNgGAWjYBSMgoEBgljwYAJCWPBgAgPtPgAzvv49QAYAAA==
   </data>
   </layer>
-  <layer name="Ground" width="40" height="10">
+  <layer id="4" name="Ground" width="40" height="10">
    <properties>
     <property name="customlayerprop" value="1"/>
     <property name="customlayerprop2" value="2"/>
@@ -50,17 +50,17 @@
   </data>
   </layer>
  </group>
- <layer name="Platforms" width="40" height="10">
+ <layer id="5" name="Platforms" width="40" height="10">
   <data encoding="base64" compression="gzip">
    H4sIAAAAAAAACmNgGAWDDfACMR8Q82MRw4f5GcgDyGbz4xEj11xy9Y+CUTAKBjcAAB+IdqlABgAA
   </data>
  </layer>
- <layer name="Details" width="40" height="10">
+ <layer id="6" name="Details" width="40" height="10">
   <data encoding="base64" compression="gzip">
    H4sIAAAAAAAACmNgGLlAGIuYBJQWRROXpNAuKSxmSkPNlaXQbHKBzADZSwiAwgkUD9IE1MkhsUUYEHGHDsSp4Sg6A3S/44orUagcKB3J4VCDDtDTGy8DwwJ+BoYDfEAMZB8AshOIdyntAdBdC3ghNAM/hE4YWBehAqCbFiDzeQeZ+2gJAHOitUlABgAA
   </data>
  </layer>
- <objectgroup color="#befdf9" draworder="index" name="Objects Layer 1">
+ <objectgroup color="#befdf9" draworder="index" id="7" name="Objects Layer 1">
   <properties>
    <property name="objLayerProp" value="true"/>
   </properties>
@@ -78,10 +78,16 @@
   <object id="20" name="Crate2" gid="23" x="60" y="345" width="226" height="226"/>
   <object id="21" name="Crate3" gid="23" x="170" y="246" width="171" height="171"/>
  </objectgroup>
- <objectgroup name="TransparentObjects" opacity="0.5">
+ <objectgroup id="8" name="TransparentObjects" opacity="0.5">
   <object id="18" name="TP1" gid="21" x="133" y="432" width="280" height="280"/>
  </objectgroup>
- <layer name="Tile Layer 5" width="40" height="10">
+ <layer id="9" name="Tile Layer 5" width="40" height="10">
+  <properties>
+   <property name="InlineString" value="This is an inline string"/>
+   <property name="MultilineString">You can press the three dots in the property editor to open a bigger text edit window.
+Pressing enter in it causes the string to contain a newline character, as well as the xml entry to be structured differently. 
+The Tiled Map Importer is unable to read this property. Deleting it fixes the import error.</property>
+  </properties>
   <data encoding="base64" compression="gzip">
    H4sIAAAAAAAACmNgGAWjYBSMglEwCkgHADV9EcVABgAA
   </data>

Source/MonoGame.Extended.Tiled/Serialization/TiledMapPropertyContent.cs

@@ -8,7 +8,12 @@ namespace MonoGame.Extended.Tiled.Serialization
         public string Name { get; set; }
 
         [XmlAttribute(AttributeName = "value")]
-        public string Value { get; set; }
+        public string ValueAttribute { get; set; }
+
+        [XmlText]
+        public string ValueBody { get; set; }
+
+        public string Value => ValueAttribute ?? ValueBody;
 
         public override string ToString()
         {