builds for .NET3.5 again

Source/Properties/AssemblyInfo.cs

@@ -32,7 +32,7 @@ using System.Runtime.InteropServices;
 //
 // You can specify all the values or you can default the Revision and Build Numbers 
 // by using the '*' as shown below:
-[assembly: AssemblyVersion("1.5.1.*")]
+[assembly: AssemblyVersion("1.5.2.*")]
 //[assembly: AssemblyFileVersion("1.0.1.*")]
 
 [assembly: CLSCompliant(true)]

Source/Svg.csproj

@@ -16,7 +16,7 @@
     <OldToolsVersion>3.5</OldToolsVersion>
     <UpgradeBackupLocation>
     </UpgradeBackupLocation>
-    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
     <IsWebBootstrapper>false</IsWebBootstrapper>
     <SccProjectName>
     </SccProjectName>

Source/SvgElement.cs

@@ -459,7 +459,7 @@ namespace Svg
 	                var evt = attr.Event.GetValue(this);
 	                
 	                //if someone has registered publish the attribute
-	                if (evt != null && !string.IsNullOrWhiteSpace(this.ID))
+	                if (evt != null && !string.IsNullOrEmpty(this.ID))
 	                {
 	                    writer.WriteAttributeString(attr.Attribute.Name, this.ID + "/" + attr.Attribute.Name);
 	                }
@@ -727,7 +727,7 @@ namespace Svg
         /// <param name="caller"></param>
         public void RegisterEvents(ISvgEventCaller caller)
         {
-            if (caller != null && !string.IsNullOrWhiteSpace(this.ID))
+            if (caller != null && !string.IsNullOrEmpty(this.ID))
             {
                 var rpcID = this.ID + "/";
 
@@ -747,7 +747,7 @@ namespace Svg
         /// <param name="caller"></param>
         public void UnregisterEvents(ISvgEventCaller caller)
         {
-        	if (caller != null && !string.IsNullOrWhiteSpace(this.ID))
+        	if (caller != null && !string.IsNullOrEmpty(this.ID))
         	{
         		var rpcID = this.ID + "/";