implemented insert for SvgElementCollection

Source/SvgElementCollection.cs

@@ -53,7 +53,14 @@ namespace Svg
         /// <param name="item">The <see cref="SvgElement"/> to be added.</param>
         public void Insert(int index, SvgElement item)
         {
+            InsertAddAndFixID(index, item, false, false);
+        }
+
+        public void InsertAddAndFixID(int index, SvgElement item, bool autoFixID = true, bool autoFixChildrenID = true, Action<SvgElement, string, string> logElementOldIDNewID = null)
+        {
+            AddToIdManager(item, autoFixID, autoFixChildrenID, logElementOldIDNewID);
             this._elements.Insert(index, item);
+            item._parent.OnElementAdded(item, index);
         }
 
         public void RemoveAt(int index)
@@ -78,6 +85,13 @@ namespace Svg
         }
 
         public void AddAndFixID(SvgElement item, bool autoFixID = true, bool autoFixChildrenID = true, Action<SvgElement, string, string> logElementOldIDNewID = null)
+        {
+            AddToIdManager(item, autoFixID, autoFixChildrenID, logElementOldIDNewID);
+            this._elements.Add(item);
+            item._parent.OnElementAdded(item, this.Count - 1);
+        }
+
+        private void AddToIdManager(SvgElement item, bool autoFixID = true, bool autoFixChildrenID = true, Action<SvgElement, string, string> logElementOldIDNewID = null)
         {
             if (!this._mock)
             {
@@ -85,7 +99,7 @@ namespace Svg
                 {
                     this._owner.OwnerDocument.IdManager.AddAndFixID(item, autoFixID, logElementOldIDNewID);
 
-            		if(!(item is SvgDocument)) //don't add subtree of a document to parent document
+                    if (!(item is SvgDocument)) //don't add subtree of a document to parent document
                     {
                         foreach (var child in item.Children)
                         {
@@ -96,10 +110,6 @@ namespace Svg
 
                 item._parent = this._owner;
             }
-
-            item._parent.OnElementAdded(item, this.Count - 1);
-
-            this._elements.Add(item);
         }
 
         public void Clear()