Archive for July, 2013

Dataset Search with LINQ

Search in datatable with relation

DataTable dt1 = GetDataTable(students);
IEnumerable seq1 = dt1.AsEnumerable();
DataTable dt2 = GetDataTable2(classDesignations);
IEnumerable seq2 = dt2.AsEnumerable();
string anthonysClass = (from s in seq1 where s.Field(“Name”) == “Anthony Adams”
from c in seq2 where (int)c[“Id”] == (int)s[“Id”]
select (string)c[“Class”]). SingleOrDefault();

Search in field

int id; id = (from s in seq1 where s.Field(“Name”) == “Anthony Adams”
select s.Field(“Id”, DataRowVersion.Current)). Single();

Update values back to dataset

DataRow row = (from s in seq1 where s.Field(“Name”) == “Anthony Adams”
select s).Single();
row.SetField(“Name”, “George Oscar Bluth”);

Categories: LINQ

Important principles of SOA (Service oriented Architecture)

SOA is based on four important concepts:-

1) Services share only schemas and contracts

Services use Schemas to represent data and contracts to understand behavior. They do not use language dependent types or classes in order to understand data and behavior. XML is used to define schemas and contracts. Due to this, there is not heavy coupling between environments.

 2) Services evolve

Change is the law of nature and services will evolve. In SOA, services can be versioned and you can host those services in new ends. For instance, you have a service called as “Search Client “which gives details based on Ticket Number and its exposed on end point “endpoint1”. Tomorrow you want make your Search Tickets service more useful by also providing an extra option of allowing him to search by passenger name. Therefore, you just declare a new end “endpoint2” with service “Search Client with phone number”. So the client who is consuming the service at end endpoint1 continues and at the other end, we have evolved our service by adding new ends endpoint2.

3)Service compatibility is policy based

Policy describes the capabilities of the system. Depending on policies, the service can degrade to match the service for the client. For instance your service needs to be hosted for two types of client one which uses Remoting as the communication methodology while other client uses DCOM. An ideal SOA service can cater to both of them according to there communication policies.

4)Boundaries are well defined

In SOA, everything is formalized. The client who is consuming the service does not need to know how the implementation of the service is done. If you look at some old methodologies of communication like DCOM. Any changes at server level the client also has to change. Therefore, the server and client implementation was so much bound that changes need to be done at all places. In SOA, the rule is if you do enhancement you do not need to change anything at the client. SOA based application only understands that there is an end point, contract, and bindings.

Note: – Just to clarify shortly about end point and contract. Any SOA service is exposed through an end point. End point defines three important aspects What, Where and How. We will understand more details of the same in the later questions.

Is Web services are the base for SOA. The answer is 50 % supported. What web services lack is the policy based Service compatibility. If you host a web service it can only serve with HTTP communication channel and SOAP message. Any other type of client trying to communicate he will not degrade it self. This is what is provided by WCF. You can host the service in one or more mode. For instance you can host a WCF service using remoting and ASMX.

Categories: .Net, WCF