New Features in Visual Basic 9.0

Wednesday, March 21, 2007



New features have been added to the language. Few of them can be listed as:

  1. Implicitly Typed Local Variables

This feature allows us to declare variables without specifying their data type. The datatypes are assigned to them based on the value assigned to these variables on the right hand side.

  1. Object and Array Initializers

The new object initializers in VB 9.0 are an expression-based form of “With” for creating complex object instances concisely. For example, we already know that the With statement simplifies access to multiple members of an object by using a member-access expression starting with a period which is evaluated as if it were preceded by the object name itself, as in

Dim MyCounty As New Country()

With MyCounty

.Name = "My County"

.Area = 555

.Population = 15432

End With

Using new object initializers above 2 statements can be clubbed together as

Dim MyCounty = New Country With { .Name = "My County ", _

.Area = 555, _

.Population = 15432 _

}

  1. Anonymous Types

VB 9.0 enables us having variables without the need to declare/define the type. All you need to be able to do is create something that looks like it and access the public fields/properties.

Some more information about anonymous types: here.

  1. Deep XML Support

LINQ to XML is a new, in-memory XML programming API designed specifically to leverage the latest .NET Framework capabilities such as the Language-Integrated Query framework. Just as query comprehensions add familiar, convenient syntax over the underlying standard .NET Framework query operators, Visual Basic 9.0 provides deep support for LINQ to XML through XML literals and XML properties.

For detailed explanation check the msdn link at the bottom of this post.

  1. Query Comprehensions

SQL like queries can now be used to perform SQL like operations using operators like Select, Order By, Where etc to get the desired data/result form collections. For this purpose query expression is used which is somewhat similar to SQL syntax, but due to some clashes with VB syntax some differences exist which should be learned.

  1. Extension Methods and Lambda Expressions

Much of the underlying power of the .NET Framework standard query infrastructure comes from extension methods and lambda expressions.

Extension methods are shared methods marked with custom attributes that allow them to be invoked with instance-method syntax. Most extension methods have similar signatures. The first argument is the instance against which method is applied, and the second argument is the predicate to apply.

Some more details about lambda expressions can be gathered form here.

  1. Nullable Types

The nullable values from the relational databases used to be inconsistent with the data types in .NET. Now we can declare different data types as nullable to overcome this inconsistency.

  1. Relaxed Delegates

In Visual Basic 9.0, binding to delegates is relaxed to be consistent with method invocation. That is, if it is possible to invoke a function or subroutine with actual arguments that exactly match the formal-parameter and return types of a delegate, we can bind that function or subroutine to the delegate. In other words, delegate binding and definition will follow the same overload-resolution logic that method invocation follows.

To have a detailed look at each of the features mentioned above, read more.

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