Invalid Token when using XPath - xpath

Question

I am making a modification to a web application using XPath, and when executed I get an error message - Invalid token!
This is basic what I am doing
public xmlNode GetSelection (SelectParams params, xmldocument docment)
{
xpathstring = string.format("Name =\'{0}' Displaytag = \'{1}' Manadatory=\'{2}', params.Name, params.Displaytag, params.Manadatory);
return document.selectsinglenode(xpathstring);
}
As you can see, I am making a string and setting values on the nodes I am trying to find against my xml document, and thus returning xml data that matches my parameters.
What is happening is that I am getting an xpathexeception error in Visual Studio and it says invalid token.
I do know that in the xml document that the parameters I am looking in the tags have double quotes, for example, Name="ABC". So, I thought the problem could be solved using an "\".
Can anyone help?
Update from comments
In the Xml Document, the tag has
attributes where they are set as
Name="ABC" Displaytag="ATag"
Manadatory="true".

Answer 1

I guess you need:
//*[#Name="ABC"][#Displaytag="ATag"][#Manadatory="true"]
Or
//*[#Name="ABC" and #Displaytag="ATag" and #Manadatory="true"]
Meaning: any element in the whole document having a Name attribute with "ABC" value, a Displaytag attribute with "ATag" value and a Manadatory attribute with "true" value.

Answer 2

The string passed as argument to SelectSingleNode() (BTW, the exact capitalization is important) is something like:
Name ='someName' Displaytag = 'someString' Manadatory='true'
This is extremely different than a syntactically legal XPath expression.
And the error message just reflects the fact that toxic food has been given to the XPath engine.
Solution: Do read at least a light XPath tutorial and then specify a correct XPath expression.

Answer 3

The string you are constructing is not a valid XPath expression. In fact, it is nothing like XPath at all.
Indeed, even if it were a valid XPath expression, constructing it this way by string concatenation is a very dangerous practice, because of the possibility of injection attacks. But I suspect that advice will fall on stony ground.