Come near VB.net (eight) Common syntax

Grammar approached VB.net (eight) Common syntax
One: Try ..... Catch.........finally.........end Try Catch Error


Put a possible error statement behind a try and, if an error occurs, execute a Catch statement,


A catch can have multiple errors that the first catch cannot catch and will be captured by the next catch statement. After all the processing is complete, the finally statement is executed.


You can use catch with one or two of the finally two in a try.........end try procedure,


Two: Protected, private, public package control


These three keywords are generally placed at the front of the statement, and are placed behind overloads and overrides.


Public is an engineering-level external access


Protected is the following internal access to the family level


Private is not providing non-local access


Three: ByVal sender as Object, ByVal e As System.EventArgs this is the most rewarding event-passing parameter. is encapsulated within two objects,
If you want to pass the corresponding arguments, look for the two objects, such as the current mouse position is E. X e.y. In VB. NET some of the events are to be written by yourself,
such as the form mouse process, the general plus this parameter in the parentheses in the back of the solution.


Four: Overloaded grammar overloads

such as: class Class1

Public Strtem As String

Overloads Public Sub Subx () Overload SUBX (a State)

Strtem= "3"

End Sub

Overloads Public Sub Subx (x As String) overload SUBX (b State)

Strtem=x

End Sub

End Class

If you call SUBX () with no parameters in the middle, VB automatically invokes the overload SUBX (a state),

Overloads Public Sub Subx () Overload SUBX (a State)

Strtem= "3"

End Sub

The result is strtem= "3."

If you call this, SUBX ("This is a different result"), then VB automatically invokes the overload SUBX (b State)

Overloads Public Sub Subx (x As String) overload SUBX (b State)

Strtem=x

End Sub

The result is strtem= "It's a different result."



You can call in a function, including in the API (of course vb.net no longer use WINAPI).



Even some of the most crucial processes are no exception: the new process (described in this Wangguorong article)

such as: class Class1

Overloads public Sub New ()

。。。。。。

。。。。。。

End Sub

Overloads public Sub New (s As String)

。。。。。。

。。。。。。

End Sub

End Class

There are also two methods of calling, such as dim as as Class1=new class, which calls a previous parameterless new procedure.

The dim asb As Class1=new Class ("string") invokes the second new procedure.



Remember, if a process or a function has only one state, it cannot be applied in this way. If you try to use the Overloads keyword, vb.net will be prompted with an error asking you to remove the overloads

Five: Overrides rewrite

such as the common Dispose process:

Overrides public Sub Dispose ()

Mybase.dispose

Components. Dispose

End Sub

Overrides represents a complete rewrite of the procedures and functions provided by the parent class

Remember, however, that using overtype is a prerequisite for using the Overrides keyword in front of the same procedure or function of the parent class

VI: MyBase.New and Mybase.dispose

Ublic Sub New ()

MyBase.New

Form1 = Me

InitializeComponent

End Sub

Overrides public Sub Dispose () '

Mybase.dispose

Components. Dispose

End Sub

These two processes are available to any new project, MyBase.New is the new process of invoking the parent class of the current class, and you can also add parameters to the overloaded new process of the parent class. Such as:

Overloads public Sub New ()


MyBase.New ()


End Sub


Overloads Public Sub New (string)


MyBase.New (String)


End Sub


Seven: Structure construction


Custom types, such as:


Structure Type1


Dim x as Y


Dim A as B


。。。。。。。


End Structure


This replaces the method used in VB6 to customize the type in Type.........end type.


Eight: return value
function functionname ()
Return X ...
End Funtion
His role is the same as the following:




function functionname ()
functionname = X ...
End Funtion