从xml元素中选择多个属性值，该属性具有与特定情况匹配的属性c＃LINQ

Question

I have XML that looks like

<?xml version="1.0"?>
   <configuration>
      <TemplateMapper>
         <Template XML="Product.xml" XSLT="sheet.xslt" Keyword="Product" />
         <Template XML="Cart.xml" XSLT="Cartsheet.xslt" Keyword="Cart" />
      </TemplateMapper>
    </configuration>

When I pass in value of attribute Keyword as "product" I want LINQ to return me value of XML and XSLT attributes as Dictionary of string and string.

I have so far tried:

               var Template="Product"
                var dictionary = (from el in xmlElement.Descendants("TemplateMapper") 
                              let xElement = el.Element("Template") 
                              where xElement != null && xElement.Attribute("Keyword").Value == Template 
                              select new
                                         {
                                             XML = el.Attribute("XML").Value, 
                                             XSLT= el.Attribute("XSLT").Value
                                         }).ToDictionary(pair => pair.XML, pair => pair.XSLT);

            KeyValuePair<string, string> templateValues = dictionary.FirstOrDefault();

It's giving be an error "Object reference not set to instance of an object". Can anyone spot what wrong am I doing? Helps really appreciated.

Answer 1

I would try following:

var dictionary = (from t in xdoc.Root.Element("TemplateMapper").Elements("Template")
                  where (string)t.Attribute("Keyword") == Template
                  select new {
                      XML = (string)t.Attribute("XML"),
                      XSLT = (string)t.Attribute("XSLT")
                  }).ToDictionary(x => x.XML, x => x.XSLT);

(string)XAttribute does not throw an exception when attribute is not found, so it's better that XAttribute.Value .

Answer 2

replace your code with this

           var Template="Product"
            var dictionary = (from el in xmlElement.Descendants("TemplateMapper") 
                          let xElement = el.Element("Template") 
                          where xElement != null && xElement.Attribute("Keyword").Value == Template 
                          select new
                                     {
                                         XML = xElement .Attribute("XML").Value, 
                                         XSLT= xElement .Attribute("XSLT").Value
                                     }).ToDictionary(pair => pair.XML, pair => pair.XSLT);

        KeyValuePair<string, string> templateValues = dictionary.FirstOrDefault();

the element you are at currently is xElement not el