Decrease memory usage on opening SVG document (#911)

* Use Concat and Join with ToArray instead of string aggregation
* Fixes #909 'Very high memory usage (and allocations)' issue

Source/SvgDocument.cs

@@ -501,7 +501,7 @@ namespace Svg
 
                             if (element.Nodes.OfType<SvgContentNode>().Any())
                             {
-                                element.Content = (from e in element.Nodes select e.Content).Aggregate((p, c) => p + c);
+                                element.Content = string.Concat((from n in element.Nodes select n.Content).ToArray());
                             }
                             else
                             {
@@ -535,7 +535,7 @@ namespace Svg
 
             if (styles.Any())
             {
-                var cssTotal = styles.Select((s) => s.Content).Aggregate((p, c) => p + Environment.NewLine + c);
+                var cssTotal = string.Join(Environment.NewLine, styles.Select(s => s.Content).ToArray());
                 var cssParser = new Parser();
                 var sheet = cssParser.Parse(cssTotal ?? string.Empty);
 

Source/Transforms/SvgTransformCollection.cs

@@ -102,7 +102,7 @@ namespace Svg.Transforms
         {
             if (Count < 1)
                 return string.Empty;
-            return (from t in this select t.ToString()).Aggregate((p, c) => p + " " + c);
+            return string.Join(" ", (from t in this select t.ToString()).ToArray());
         }
     }
 }

doc/ReleaseNotes.md

@@ -3,6 +3,9 @@ The release versions are NuGet releases.
 
 ## Unreleased (master)
 
+### Performance
+* reduce very high memory usage (see [#909](https://github.com/svg-net/SVG/issues/909))
+
 ### Fixes
 * fixed color blend position (see [#902](https://github.com/svg-net/SVG/issues/902))