Dynamics CRM- update record of contact entity - dynamics-crm-2013

Question

I have created contact record using ASP.NET. Now I need to Check if the contact record exists. If exists, update the same record. Through advance find have downloaded FetchXML and added to my FetchXML variable. Please suggest the logic. Below is my code.
// Establish a connection to crm and get the connection proxy
string connectionString = "xyz; Username= xyz ;Password=xyz";
CrmConnection connect = CrmConnection.Parse(connectionString);
OrganizationService service;
using (service = new OrganizationService(connect))
{
WhoAmIRequest request = new WhoAmIRequest();
Guid userId = ((WhoAmIResponse)service.Execute(request)).UserId;
ContactDetails contact = new ContactDetails();
//Check if the contact record exists . If exists , update the same record.
//Fecthxml query
string fetchXml = #" <fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='false'>
<entity name='contact'>
<attribute name='fullname' />
<attribute name='parentcustomerid' />
<attribute name='telephone1' />
<attribute name='emailaddress1' />
<attribute name='contactid' />
<order attribute='fullname' descending='false' />
<filter type='and'>
<condition attribute= 'mobilephone' operator='not-null' />
</filter>
</entity>
</fetch>" ;
FetchExpression query = new FetchExpression(fetchXml);
EntityCollection results = service.RetrieveMultiple(query);
if (results.Entities.Count > 0)
{
Entity contactRecord = results[0];
contactRecord["firstname"] = contactInfo.FirstName;
contactRecord["lastname"] = contactInfo.LastName;
contactRecord["emailaddress1"] = contactInfo.EmailId;
contactRecord["mobilephone"] = contactInfo.MobilePhone;
contactRecord["address1_line1"] = contactInfo.Street1;
contactRecord["address1_line2"] = contactInfo.Street2;
contactRecord["address1_line3"] = contactInfo.Street3;
contactRecord["address1_city"] = contactInfo.City;
service.Update(contactRecord);
}
//Else, Create the contact record
else
{
Entity entity = new Entity();
entity.LogicalName = "contact";
entity["firstname"] = contactInfo.FirstName;
entity["lastname"] = contactInfo.LastName;
entity["emailaddress1"] = contactInfo.EmailId;
entity["mobilephone"] = contactInfo.MobilePhone;
entity["address1_line1"] = contactInfo.Street1;
entity["address1_line2"] = contactInfo.Street2;
entity["address1_line3"] = contactInfo.Street3;
entity["address1_city"] = contactInfo.City;
entity["address1_stateorprovince"] = contactInfo.State;
entity["address1_country"] = contactInfo.Country;
entity["spousesname"] = contactInfo.SpouseName;
entity["birthdate"] = contactInfo.Birthday;
entity["anniversary"] = contactInfo.Anniversary;
//Create entity gender with option value
if (contactInfo.Gender == "Male")
{
entity["gendercode"] = new OptionSetValue(1);
}
else
{
entity["gendercode"] = new OptionSetValue(2);
}
//entity["familystatuscode"] = contactInfo.MaritalStatus;
if (contactInfo.MaritalStatus == "Single")
{
entity["familystatuscode"] = new OptionSetValue(1);
}
else
{
entity["familystatuscode"] = new OptionSetValue(2);
}
service.Create(entity);
}
}
// Create the entity

Answer 1

your logic seems ok, with the exception of the FectchXML query. The way you have your code, you will always end up updating the first record retrieved that has its mobilephone field filled. That does not seem a good way to check if a contact already exists.
I suggest you to change the filter of your fetch. In your filter condition you have to use an attribute that represents uniqueness for all contacts.
Apart of this your code looks ok.

Answer 2

Like nunoalmeieda says, you need to have a better way to ascertain if the Contact already exists. A common way of identifying if the Contact already exists would be to check if the email address already exists as it is very unlikely that two people will have the same email address.
I have updated your basic code to show how it is done with FetchXML.
<fetch version="1.0" output-format="xml-platform" mapping="logical" distinct="false">
<entity name="contact">
<attribute name='fullname' />
<attribute name='parentcustomerid' />
<attribute name='telephone1' />
<attribute name='emailaddress1' />
<attribute name='contactid' />
<order attribute="fullname" descending="false" />
<filter type="and">
<condition attribute="emailaddress1" operator="eq" value=contactInfo.EmailId />
</filter>
</entity>
</fetch>
The logic here is that I am checking if the value of emailaddress1 (field in the contact entity of CRM) is equal to the value of your contactInfo.EmailId. I am assuming that contactInfo is the record that you get from ASP.NET.
The rest of your code is fine (I have formatted it a bit to make the question more readable).