Advanced c# and .NET Interview Questions and Answers Part 8

1. ) What is a DiffGram Explain ?                                                                                              

• A DiffGram is an XML format that is used to identify current and original versions of data elements.
•  When sending and retrieving a DataSet from an XML Web service, the DiffGram format is implicitly used.
• The DataSet uses the DiffGram format to load and persist its contents, and to serialize its contents for transport across a network connection. When a DataSet is written as a DiffGram, it populates the DiffGram with all the necessary information to accurately recreate the contents, though not the schema, of the DataSet, including column values from both the Original and Current row versions, row error information, and row order. 

2. ) How to use  DiffGram in xml web services ?                                                                 

  There are following way to use DiffGram in xml web Services.
<?xml version="1.0"?>
<diffgr:diffgram
xmlns:msdata="urn:schemas-microsoft-com:xml-msdata"
xmlns:diffgr="urn:schemas-microsoft-com:xml-diffgram-v1"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<DataInstance>
</DataInstance>

<diffgr:before>
</diffgr:before>

<diffgr:errors>
</diffgr:errors>
</diffgr:diffgram>

Descriptions:-
The DiffGram Format is divided into three sections as given below:-
1.) <DataInstance>
The name of this element, Data Instance, is used for explanation purposes in this documentation. A DataInstance element represents a DataSet or a row of a DataTable. Instead of Data Instance, the element would contain the name of the DataSet or DataTable. This block of the DiffGram format contains the current data, whether it has been modified or not. An element, or row, that has been modified is identified with the diffgr: has Changes annotation. 
2.) <diffgr:before
This block of the DiffGram format contains the original version of a row. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation
3.) <diffgr:errors>

This block of the DiffGram format contains error information for a particular row in the DataInstance block. Elements in this block are matched to elements in the DataInstance block using the diffgr:id annotation. 

3. ) Where are the IIS log files stored ?                                                                                   
C:\WINDOWS\system32\Logfiles\W3SVC1
               OR
C:\winnt\system32\LogFiles\W3SVC1

4. ) What are the different IIS authentication modes in IIS 6.0 ?                                
There are different variety of authentication schemes of IIS.

• Anonymous (enabled by default) authentication
• Basic authentication
• Digest authentication
• Integrated Windows authentication (enabled by default) 
• Client Certificate Mapping 

5. ) In which process does IIS (.exe file) runs ?                                                                   

inetinfo.exe is the Microsoft IIS server running, handling ASP.NET requests among other things.When an ASP.NET request is received (usually a file with .aspx extension), the ISAPI filter aspnet_isapi.dll takes care of it by passing the request to the actual worker process aspnet_wp.exe. 

6. ) What are the IIS isolation Levels ?                                                                                    
There are three isolation levels of IIS 5.0 .

• Low(IIS Process)
• Medium(pooled)
• High(isolated)

7. ) How do I upload a file from my ASP.NET page ?                                                         
ReadDetails

8. ) How to send an email message from  ASP.NET page ?                                              
ReadDetails...

9. ) Can I pass SOAP messages through remoting?                                                            
Yes.
10. ) What is CAO and SAO Explain?                                                                                        
CAO means client activated Objects and SAO means Server activated objects.

• Client Activated objects are those remote objects whose Lifetime is directly Controlled by the client. This is in direct contrast to SAO. Where the server, not the client has complete control over the lifetime of the objects. 
• Client activated objects are instantiated on the server as soon as the client request the object to be created. Unlike as SAO a CAO doesn’t delay the object creation until the first method is called on the object. (In SAO the object is instantiated when the client calls the method on the object) 

11. ) What is singleton and singlecall Explain?                                                                     

• Singleton types never have more than one instance at any one time. If an instance exists, all client requests are serviced by that instance.
• Single Call types always have one instance per client request. The next method invocation will be serviced by a different server instance, even if the previous instance has not yet been recycled by the system. 

12. ) Are Web Services a replacement for other distributed computing platforms? 

No. Web Services is just a new way of looking at existing implementation platforms.

13. ) In webservice,Suppose we have to display 20 rows from a table who is best Dataset or DataReader ?
A WebService supports only Dataset. So Dataset is used,not DataReader.

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