Error in TripleStore loadfrom file

The LoadFromFile() method on a Triple store assumes a dataset file i.e. NQuads, TriG or TriX so when you try and load a RDF graph it assumes it is a dataset and uses the wrong parser.

What you want to do instead is the following:

TripleStore store = new TripleStore();
Graph g = new Graph();
g.LoadFromFile("example.rdf");
store.Add(g);

The LoadFromFile() method on a Graph expects a graph file so will correctly recognize the format and select the correct parser.

I do not know what's causing the error since your RDF/XML code validates, but I see a number of problems in your RDF file:

1. www.CarOntology is not a valid domain name;
2. Http://www.CarOntology/CarSchema# starts with a capital letter and it should not;
3. many of the literal values are starting or ending with a space (so if I'm searching for a car made in 2006, for instance, I wouldn't find any because you've put a space in the value);
4. it is not possible to use namespace prefixes inside the rdf:about or rdf:resource attribute values (e.g., rdf:about="car:Car1" should be replaced by rdf:about="Http://www.CarOntology/CarSchema#Car1");
5. for the properties car:Color and car:Kind, you use a '#' in the literal values but it would make more sense to simply write "Blue" rather than " #Blue ", unless your intention was to use a URI, in which case it should be <car:Color rdf:resource="#Blue"/>.

Moreover, you could be more concise for the type declaration and simply write:

<rdf:type rdf:resource="Http://www.CarOntology/CarSchema#Car"/>

instead of:

<rdf:type>
  <rdf:Description rdf:about="car:Car"/>
</rdf:type>

Remark: I do not want to edit your code to format it better because maybe it's important to keep the exact source code, but this is what it looks like if formatted nicely:

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF xmlns:car="Http://www.CarOntology/CarSchema#"
         xmlns:usr="Http://www.Users/UserIns#"
         xmlns:owl="http://www.w3.org/2002/07/owl#"
         xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
  <rdf:Description rdf:about="car:Car1">
    <rdf:type>
      <rdf:Description rdf:about="car:Car"/>
    </rdf:type>
    <car:CarNo>123456</car:CarNo>
    <car:Model> Mitsubishi Lancer </car:Model>
    <car:ModelYear> 2006 </car:ModelYear>
    <car:Kind> #Sedan </car:Kind>
    <car:Color> #Blue </car:Color>
    <car:KiloMeter> 40000</car:KiloMeter>
    <car:Price> 800000 </car:Price>
    <car:Imager> Http://www.MyWebCar/Photo/Car1.jpg </car:Imager>
    <car:Phone>011-22323433</car:Phone>
    <car:Mobile> 0944345234</car:Mobile>
    <car:CreatedBy rdf:resource="usr:User1"/>
  </rdf:Description>
  <rdf:Description rdf:about="car:Car2">
    <rdf:type>
      <rdf:Description rdf:about="car:Car"/>
    </rdf:type>
    <car:CarNo>3452345</car:CarNo>
    <car:Model> Toyota Corola </car:Model>
    <car:ModelYear> 2007 </car:ModelYear>
    <car:Kind> #Sedan </car:Kind>
    <car:Color> #Red </car:Color>
    <car:KiloMeter> 60000</car:KiloMeter>
    <car:Price> 850000 </car:Price>
    <car:Imager> Http://www.MyWebCar/Photo/Car2.jpg </car:Imager>
    <car:Phone>011-26876875</car:Phone>
    <car:Mobile> 0944687634</car:Mobile>
    <car:CreatedBy rdf:resource="usr:User2"/>
  </rdf:Description>
</rdf:RDF>