var temp2 = temp1.Element("staticContent");
            if (temp2 != null)
            {
                string str = "<remove fileExtension=\".svg\" />\r\n               <mimeMap fileExtension=\".svg\" mimeType=\"image/svg+xml\" />\r\n               <remove fileExtension=\".nupkg\" />\r\n               <mimeMap fileExtension=\".nupkg\" mimeType=\"application/zip, application/octet-stream\" />\r\n               <remove fileExtension=\".webm\" />\r\n               <mimeMap fileExtension=\".webm\" mimeType=\"video/webm\" />\r\n               <remove fileExtension=\".mp4\" />\r\n               <mimeMap fileExtension=\".mp4\" mimeType=\"video/mp4\" />
 
";
                temp2.AddFirst(XElement.Parse(str));
            }

必須把多個節點從，拆分開來，逐個添加

linq to xml There are multiple root elements.