VB.NET Brackets () {} [] <>

Question

Can someone please fill in the blanks for me, including a brief description of use and perhaps a code snippet? I'm well aware of the top two in particular, but a little hazy on the last one especially:

• () - Used for calling a function, object instantiation, passing parameters, etc.
• {} - Used for defining and adding elements to arrays or sets.
• [] - Used for forcing an object to be treated as a type rather than keyword.
• <> - Used for... ?

For Example, I see stuff like this all the time, but still not quite sure what the brackets means...

<TemplateContainer(GetType(TemplateItem))> _
Public Property MessageTemplate As ITemplate

Solution 1

In this case it's used for the Attribute declaration. It can also be used in XML Literals as follows:

<TestMethod>
Public Sub ThisIsATest()
  If 1 <> 0 Then
    Dim foo = <root>
                <child>this is some XML</child>
              </root>
  End If
End Sub

Solution 2

VB.net uses parentheses for, among other things, arithmetic groupings and function parameters (both of which use parentheses in C#), as well as array subscripts and default-property parameters (both of which use brackets in C#), (indexers), etc. It also uses (Of ... ) to enclose a list of types (which would be enclosed in < ... > in C#, with no "Of" keyword.

Braces are used for array or set initialization expressions, and are also used when defining a generic type with multiple constraints (e.g. (Of Foo As {IEnumerable, IDisposable, Class})). Note that the latter usage is only permitted in constraints; it is alas not possible to e.g. Dim MyThing As {IEnumerable, IDisposable, Class}).

Braces are now also used for the New With {} construct:

Dim p = New Person With {.Name = "John Smith", .Age = 27}
Dim anon = New With {.Name = "Jack Smythe", .Age = 23}

Square brackets are used to enclose identifiers whose spelling would match that of a reserved word. For example, if a class defined a method called Not (perhaps the class was written in a language without a keyword Not), one could use such a method within VB by enclosing its name in square brackets (e.g. someVariable = [Not](5)). In the absence of the square brackets, the above expression would set someVariable to -6 (the result of applying the vb.net Not operator to the value 5).

Angle brackets, as noted elsewhere, are used for attributes. Note that in many cases, attributes are placed on the line above the thing they affect (so as to avoid pushing the affected variable past the right edge of the screen). In older versions of vb, such usage requires the use of a line-continuation mark (trailing underscore).

Angle brackets are also used for XML Literals and XML Axis Properties:

Dim xml = <simpleTag><anotherTag>text</anotherTag></simpleTag>
Console.WriteLine(xml.<anotherTag>.First.Value)

Solution 3

In VB.Net, <> is used to enclose Attributes.

Solution 4

VB.NET uses <> for attributes as well as to indicate "does not equal" (!=)

In your example it is just enclosing attributes. That same code in C# would be

[TemplateContainer(GetType(TemplateItem))]
public ITemplate MessageTemplate { get; set; }

This attribute is used in developing templated controls, which separate data from presentation. In other words, a templated control can retain the same functionality while changing it's appearance.

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