need example of small DB embeded in the application it self

I admit that I have not written a program that uses XML that has the equivalent of more than one table, but .Net's support of XML is so extensive that it is virtually impossible that primary keys are difficult to do using XML. See Walkthrough: Data Binding to a Custom Business Object. It is a sample web application, but the XML could be used in a desktop application too.

A primary key in XML is apparently specified using a Unique Element; see Mapping unique XML Schema (XSD) Constraints to DataSet Constraints. Also see Map Relations Specified for Nested Elements (ADO.NET)

DataTable.WriteXml Method shows another way to store XML from data in memory.

There are very many options available using .Net. One big question is if you need to save the data.

If you need to save the data as a database, you can use SQL Server Compact Edition (CE). It is used in Windows Mobile but it can also be used in a desktop application. It is free.

You can use XML to store the data. Use the XmlSerializer Class to read and write the data.

In your program, you can use many classes in the System.Data Namespace (), such as the DataSet Class (System.Data) and DataTable Class (System.Data). You can create objects of those classes in memory during execution and get and put the data from wherever you need to. The .Net classes and framework offer many ways to work with "objects"; it is possible to write a simple program that uses objects, and there are complete books about how to use objects.

Microsoft uses the term "bound" to refer to forms and controls that can automatically get and put data. That is a bit of an over-simplification and you need to learn about how it works. You can read data into and write data from XML and store the data in memory as objects and bind forms to the objects.

Also look at Language-Integrated Query (LINQ) and LINQ. It is like a complete database system all in memory.

Also there is a lot to read in Accessing Data. See Data Walkthroughs for some examples of things that can be done; not all examples use SQL Server.

Note also that if you choose to use SQL CE (Compact Edition), most SQL Server samples can be converted to using SQL CE by changing the classes to use the SqlCe prefix instead of Sql; for example, the SqlCeConnection Class is the CE quivalent of the SqlConnection Class. Also, for connection strings, a SQL CE connection string usually consists of only a database file path, as in:

Data Source=C:\Temp\Temporary.sdf

Hi Kirtan

thank you for your info,
I will come and take a try Sql Lite

regard
han