how i can check if this header exists?

I am trying to check in my xml file if HeaderReportUnit exists, how i can check if this Header exists ? I am using 2.0 assembly , really thanks for help

 <?xml version="1.0" encoding="UTF-8" ?> 
- <HeadReportUnit>
- <Title>
  <ModuleNum>ModuleNum</ModuleNum> 
  <hdstSetPos>hdstSetPos</hdstSetPos> 
  <hdstNzlName>hdstNzlName</hdstNzlName> 
  <nzavSpecName>nzavSpecName</nzavSpecName> 
  <nzavNzlDiameter>nzavNzlDiameter</nzavNzlDiameter> 
  <nzavNzlSizeX>nzavNzlSizeX</nzavNzlSizeX> 
  <nzavNzlSizeY>nzavNzlSizeY</nzavNzlSizeY> 
  <nzavNzlType2>nzavNzlType2</nzavNzlType2> 
  </Title>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 1</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 2</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 3</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlTy开发者_如何学Pythonpe2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 4</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 5</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 6</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 7</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 8</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 9</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</nzavNzlSizeX> 
  <nzavNzlSizeY>0.6</nzavNzlSizeY> 
  <nzavNzlType2>Standard</nzavNzlType2> 
  </Unit>
- <Unit>
  <ModuleNum>1</ModuleNum> 
  <hdstSetPos>1- 10</hdstSetPos> 
  <hdstNzlName>R07-007-070</hdstNzlName> 
  <nzavSpecName>AA05700</nzavSpecName> 
  <nzavNzlDiameter>0.0</nzavNzlDiameter> 
  <nzavNzlSizeX>0.7</

nzavNzlSizeX

You could select the node with an XPathNavigator and see if there is a result.

For example:

FileStream stream = new FileStream("c:\\file.xml", FileMode.Open);
XPathDocument document = new XPathDocument(stream);
XPathNavigator navigator = document.CreateNavigator();
XPathNodeIterator node = navigator.Select("/HeadReportUnit");
if (node.Count > 0)
{
   // do stuff
}