Auto-Implemented Properties in VB.NET

Making QR Code 2d barcode in VB.NET Auto-Implemented Properties

It is very common to need to create private variables with public accessor methods. In VB.NET you probably have written something like the following (although bet you haven t had the need to create a Tiger class): Public Class Tiger Private _Name As String Property Name() As String Get Return _Name End Get Set(ByVal Name As String) _Name = Name End Set End Property End Class You can now use the following syntax to get the compiler to generate a private backing field like in C#: Public Class AdvancedTiger Property Name() As String End Class The old syntax is of course still supported.

Adding items to a collection in VB was previously slightly tedious, and would be done with code such as the following:

Dim ThingsNotFoundInEmploymentAgents As New List(Of String) ThingsNotFoundInEmploymentAgents.Add( technical knowledge ) ThingsNotFoundInEmploymentAgents.Add( honesty ) ThingsNotFoundInEmploymentAgents.Add( a reflection ) Collections can now be initialized using the following syntax with the new From keyword: Dim TraitsNotFoundInJobAgents As New List(Of String) From { "technical knowledge", "honesty", "a reflection" }

Array literals allow the compiler to infer an array. In the following example the array will be automatically typed as an integer: Dim myArray = {2, 3, 5} Personally I prefer to specify the type, as I think it makes your intention clearer, but the decision is now yours.

Until this release you could not declare jagged arrays in VB.NET easily and would have to resort to code similar to the following: Dim firstSetOfValues() As Integer = {1, 2, 3} Dim seondSetOfValues() As Integer = {4, 5} Dim allValues()() As Integer = {firstSetOfValues, seondSetOfValues} However, you can now use the following syntax: Dim allValuesNewWay = {({"1", "2", "3"}), ({"4", "5"})}

Optional parameters can now be nullable: Public Sub MyFunction(ByVal Val1 As String, Optional ByVal z As Integer = Nothing) End Sub

Many of the language enhancements we have looked at so far can greatly ease working with legacy code such as COM objects. Let s look in more detail as to by adapting an example from Scott Hansleman s blog (www.hanselman. com/blog/CLRAndDLRAndBCLOhMyWhirlwindTourAroundNET4AndVisualStudio2010Beta1.aspx).

In Scott s example, the Microsoft Office API is used to open an existing text file. To see this example, add the following code and a reference to Microsoft.Office.Interop.Word then take a look at the intellisense for the Open() method (see Figure 3-1: eek!): using Microsoft.Office.Interop.Word. var WordApplication = new Microsoft.Office.Interop.Word.Application();WordApplication.Visible = true; object missing = System.Reflection.Missing.Value; object file =@"c:\test.txt"; object visible = true; object readOnly = false; Document aDoc = WordApplication.Documents.Open( ref file,ref missing,ref readOnly,ref missing, ref missing,ref missing,ref missing,ref missing, ref missing,ref missing,ref missing,ref visible, ref missing,ref missing,ref missing,ref missing);

.NET optional and named parameters make this much easier: var betterWay = WordApplication.Documents.Open(file, ReadOnly: true, Visible: true); betterWay.Activate(); The new dynamic functionality (which we will look at shortly) can also make your code more readable by allowing you to infer many casting operations. For example, the compiler can now work out the type of object you are using (duck typing) allowing code such as ((Excel.Range) excel.Cells[1, 1]).Value2 = "Excell-ent!"; to be rewritten as: excel.Cells[1, 1].Value = "Excell-ent!"; Not hugely different, but much more readable.

Another COM-related change worth mentioning is that you no longer need PIA files. In previous versions of Visual Studio, when a COM component was referenced, Visual Studio would create an additional assembly to describe the COM DLL to the CLR (a PIA or Primary Interop Assembly). Unfortunately, these PIA files could get pretty large as they described every method of the COM object even if you were not using them. In VS2010 to stop Visual Studio generating PIA files simply set the Embed Interop Types property to True in Solution Explorer.