I am trying to do a XML parser which will extract data from a website using REST service, the protocol for communication is HTTP, the data I get is in XML format, and I get to the data I need after several requests to different addresses on the server. I need to parse this data to c# objects so I can operate with them lately. The information on the server is on 5 levels( I am willing to make work only 4 of them for know) 1-List of vendors 2-List of groups 3-List of subgroups 4-List of products 5-List of full information about products After I get to 4th level I need to check if the product is in my database or if it has different details so I can add or update it.
With "GET" request to a server I get XML with this structure:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<vendors>
<vendor>
<id>someID</id>
<name>someName</name>
</vendor>
<vendor>
<id>someId1</id>
<name>somename1</name>
</vendor>
</vendors>
XML structure for groups is the same :
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<groups vendor_id="43153185318">
<group>
<id>someID</id>
<name>someName</name>
</group>
<group>
<id>someId1</id>
<name>somename1</name>
</group>
The XML structure is analogical for subgroups and products, except that for products I have more elements like catalog_num, price etc.
I made the classes as follows :
public class VendorList
{
public List<Vendor> vendor_list { get; set; }
public VendorList()
{
vendor_list = new List<Vendor>();
}
}
public class Vendor
{
public string id { get; set; }
public string name { get; set; }
public List<Group> groups_list { get; set; }
public Vendor()
{
id = "N/A";
name = "N/A";
groups_list = new List<Group>();
}
}
public class Group
{
public string id { get; set; }
public string name { get; set; }
public List<SubGroup> subgroup_list { get; set; }
public Group()
{
id = "N/A";
name = "N/A";
subgroup_list = new List<SubGroup>();
}
}
public class SubGroup
{
public string id { get; set; }
public string name { get; set; }
public List<Product> product_list { get; set; }
public SubGroup()
{
id = "N/A";
name = "N/A";
product_list = new List<Product>();
}
}
public class Product
{
public string available { get; set; }
public string catalog_num { get; set; }
public string code { get; set; }
public string currency { get; set; }
public string description { get; set; }
public string haracteristics { get; set; }
public string product_id { get; set; }
public string model { get; set; }
public string name { get; set; }
public string price { get; set; }
public string price_dds { get; set; }
public string picture_url { get; set; }
public Product()
{
available = "N/A";
catalog_num = "N/A";
code = "N/A";
currency = "N/A";
description = "N/A";
haracteristics = "N/A";
product_id = "N/A";
model = "N/A";
name = "N/A";
price = "N/A";
price_dds = "N/A";
picture_url = "N/A";
}
}
and the Parser method like this :
public static void FillVendor(string url)
{
string result = GetXMLstream(url);
var vendors = new VendorList();
XmlDocument doc = new XmlDocument();
doc.Load(new StringReader(result));
doc.Save(@"D:/proba/proba.xml");
XDocument d = XDocument.Load(@"D:/proba/proba.xml");
vendors.vendor_list = (from c in d.Descendants("vendor")
select new Vendor()
{
id = c.Element("id").Value,
name = c.Element("name").Value
}).ToList<Vendor>();
foreach (Vendor v in vendors.vendor_list)
{
FillGroups(v.id);
}
}
public static void FillGroups(string vendorID)
{
string url = "main address" + vendorID;
string result = GetXMLstream(url);
var group = new Vendor();
XmlDocument doc = new XmlDocument();
doc.Load(new StringReader(result));
doc.Save(@"D:/proba/proba1.xml");
XDocument d = XDocument.Load(@"D:/proba/proba1.xml");
group.groups_list = (from g in d.Descendants("group")
select new Group()
{
id = g.Element("id").Value,
name = g.Element("name").Value
}).ToList<Group>();
foreach (Group g in group.groups_list)
{
FillSubGroup(vendorID, g.id);
}
}
public static void FillSubGroup(string vendorID, string groupID)
{
string url = "main address" + vendorID+"/"+groupID;
string result = GetXMLstream(url);
var subgroup = new Group();
XmlDocument doc = new XmlDocument();
doc.Load(new StringReader(result));
doc.Save(@"D:/proba/proba2.xml");
XDocument d = XDocument.Load(@"D:/proba/proba2.xml");
subgroup.subgroup_list = (from g in d.Descendants("subgroup")
select new SubGroup()
{
id = g.Element("id").Value,
name = g.Element("name").Value
}).ToList<SubGroup>();
foreach (SubGroup sb in subgroup.subgroup_list)
{
FillProduct(vendorID, groupID, sb.id);
}
}
public static void FillProduct(string vendorID,string groupID,string subgroupID)
{
string url = "main address" + vendorID + "/" + groupID+"/"+subgroupID;
string result = GetXMLstream(url);
var product = new SubGroup();
XmlDocument doc = new XmlDocument();
doc.Load(new StringReader(result));
doc.Save(@"D:/proba/proba2.xml");
XDocument d = XDocument.Load(@"D:/proba/proba2.xml");
product.product_list = (from g in d.Descendants("subgroup")
select new Product()
{
available = g.Element("available").Value,
catalog_num = g.Element("catalog_num").Value,
code = g.Element("code").Value,
currency = g.Element("currency").Value,
description = g.Element("description").Value,
haracteristics = g.Element("haracteristics").Value,
product_id = g.Element("id").Value,
model = g.Element("model").Value,
name = g.Element("name").Value,
price = g.Element("price").Value,
price_dds = g.Element("price_dds").Value,
picture_url = g.Element("small_picture").Value,
}).ToList<Product>();
}
But after finishing parsing I try to check if my Lists are populated with objects, but I get an error which says that they are null "NullReferenceException" So my question is did I make classes properly and is my parsing method right ( you can suggest how to parse the xml without creating a file on my computer) and if I didn't where is my mistake and how should I make it work properly? Thanks in advance!
