how to replace xml elements with another xml elements in c#?

[gomezmule]

This is my two xml document.This xml is stored in paraouterXml string.\[code\]<w:tbl> <w:tblPr> </w:tblPr> <w:tblGrid> </w:tblGrid></w:tbl>\[/code\]This xml is stored in tblMetaInfo string.\[code\]<root> <w:tblPr> <w:tblStyle w:val="TableGrid" /> <w:tblW w:w="0" w:type="auto" /> <w:tblLook w:val="04A0" /> </w:tblPr> <w:tblGrid> <w:gridCol w:w="1947" /> <w:gridCol w:w="1947" /> </w:tblGrid></root>\[/code\]So,here i want to replace paraouterXml's \[code\]<w:tblPr>,<w:tblGrid>\[/code\] with tblMetaInfo's \[code\]<w:tblPr>,<w:tblGrid>\[/code\] elements.This is c# code...\[code\]XmlDocument xDoc = new XmlDocument();xDoc.LoadXml(table.OuterXml);XmlNode newNode = xDoc.DocumentElement;XmlNodeList tblPrNode = xDoc.GetElementsByTagName("w:tblPr");tblPrNode[0].RemoveAll();XmlNodeList tblGridNode = xDoc.GetElementsByTagName("w:tblGrid");tblGridNode[0].RemoveAll();XmlDocument xDoc1 = new XmlDocument();xDoc1.LoadXml(tblMetaInfo);XmlNode newNode1 = xDoc1.DocumentElement;XmlNodeList tblPrNode1 = xDoc1.GetElementsByTagName("w:tblPr");XmlNodeList tblGridNode1 = xDoc1.GetElementsByTagName("w:tblGrid");tblPrNode[0].ReplaceChild(tblPrNode1[0], tblPrNode[0]);tblGridNode[0].ReplaceChild(tblGridNode1[0], tblGridNode[0]);\[/code\]But it throwing some error...Please guide me to get out of this issue...