C# 3.0 Specifications.

C# 3.0 ("C# Orcas") introduces several language extensions that build on C# 2.0 to support the creation and use of higher order, functional style class libraries. The extensions enable construction of compositional APIs that have equal expressive power of query languages in domains such as relational databases and XML. The extensions include:
· Implicitly typed local variables, which permit the type of local variables to be inferred from the expressions used to initialize them.
· Extension methods, which make it possible to extend existing types and constructed types with additional methods.
· Lambda expressions, an evolution of anonymous methods that provides improved type inference and conversions to both delegate types and expression trees.
· Object initializers, which ease construction and initialization of objects.
· Anonymous types, which are tuple types automatically inferred and created from object initializers.
· Implicitly typed arrays, a form of array creation and initialization that infers the element type of the array from an array initializer.
· Query expressions, which provide a language integrated syntax for queries that is similar to relational and hierarchical query languages such as SQL and XQuery.
· Expression trees, which permit lambda expressions to be represented as data (expression trees) instead of as code (delegates).

I reckon it should be a must read for all C# programmer(especially for those who are planning to use LINQ, cause features like Extension Method, Anonymous Type, Lamda Expression are built for LINQ, these features work as an infrastructure for LINQ )

Btw. It is just 25 pages document, so won’t be taking much time to finish it, enjoy reading .. -:)
You can find the document at http://msdn.microsoft.com/en-us/library/ms364047(VS.80).aspx#cs3spec_topic4

How JET( OLE DB) decide the Excel Column type ?

Few days back, I was working on a tool( this tool would be using in the other countries as well) which was using Excel as a Data Source and I was using OLE DB( JET ) to communicate with the Excel.

However, an interesting issue came up while using the tool in China, whenever somebody enters Chinese char thru the tool gets the ever helping error message “Multi Step generated Error, check each status value”.

While investigating the issue, it came up that the Column type is the culprit, JET was setting the column type as ADVARCHAR, and to assign a Chinese char( read UNICODE ) the column type has to be ADVARWCHAR, but the question here is how to set column type in Excel ? so how does JET decide a Column type ?

What JET do is…it scans a number of rows( default is 8, goes by the value set in Hkey_Local_Machine/Software/Microsoft/Jet/4.0/Engines/Excel/ TypeGuessRows ) for each column and decide the column type, for example a column has 8 rows with numeric data, JET will set the data type as numeric, but consider a case where a column has 3 rows with numeric data and rest 5 with char data, what will be the type of the column ? JET will set the column type as ‘VARCHAR’.

Well, this is not all, there is one more registry key which also plays a very important role here, Hkey_Local_Machine/Software/Microsoft/Jet/4.0/Engines/ Excel/ImportMixedTypes … if the value of this key is ‘Majority Type’ then in the above case JET will set the column type as VARCHAR, however if the value of ‘ImportMixedTypes’ is ‘Text’ then JET will set the column type as UNICODE VARCHAR or ADVARWCHAR( irrespective of the column values)

However, as per JET documentation, we can override the registry setting thru the Connection String, if we set IMEX=1( as part of Extended Properties), the JET will set the all column type as UNICODE VARCHAR or ADVARWCHAR irrespective of ‘ImportMixedTypes’ key value.hey