The internal fields ___diagonalUp__ and ___diagonalDown__ fields of the class __ExcelBorderXml__ are not parsed from Xml, when opening an excel file.
This leads to the effect, that programmatical cells know nothing about their diagonal borders, until these are set explicitelly.
To fix the issue I suggest adding following two lines of code to the ExcelBorderXml constructor
```
_diagonalUp = GetXmlNodeBool(diagonalUpPath);
_diagonalDown = GetXmlNodeBool(diagonalDownPath);
```
The constructor looks afterall as following:
```
internal ExcelBorderXml(XmlNamespaceManager nsm, XmlNode topNode) :
base(nsm, topNode)
{
_left = new ExcelBorderItemXml(nsm, topNode.SelectSingleNode(leftPath, nsm));
_right = new ExcelBorderItemXml(nsm, topNode.SelectSingleNode(rightPath, nsm));
_top = new ExcelBorderItemXml(nsm, topNode.SelectSingleNode(topPath, nsm));
_bottom = new ExcelBorderItemXml(nsm, topNode.SelectSingleNode(bottomPath, nsm));
_diagonal = new ExcelBorderItemXml(nsm, topNode.SelectSingleNode(diagonalPath, nsm));
_diagonalUp = GetXmlNodeBool(diagonalUpPath);
_diagonalDown = GetXmlNodeBool(diagonalDownPath);
}
```
Best regadrs,
Ivan