vb_20130911

macro
grammer
[Public | Private] Sub name [(arglist)] 
[statements]
[Exit Sub]
[statements]
End Sub
[accessibility] Sub subname[(argumentlist)]
   'Statements of the Sub procedure go here.
End Sub
[Optional] [ByVal|ByRef] [ParamArray] argumentname As datatype
Optional [ByVal|ByRef] argumentname As datatype = defaultvalue
deliver value or reference
[Call] subname[(argumentlist)]
Sub TellOperator(ByVal Task As String)
   Dim Stamp As Date      ' Stamp is local to TellOperator.
   Stamp = TimeOfDay()    ' Get current time for time stamp.
   'Use MessageBox class of System.Windows.Forms namespace.
   MessageBox.Show("Starting " & Task & " at " & CStr(Stamp))
End Sub
Dim declare variables and allocate storage space.
Dim [WithEvents] varname[([subscripts])] [As [New] type] [, [WithEvents] varnam 
[([subscripts])] [As [New] type]]...
Call TellOperator("file update")
Option Explicit
must be declared
can be execute success 
Option Explicit
Private Sub Command1_Click()
Dim a As String
a = "tttt"
MsgBox (a)
End Sub
Private Sub Command1_Click()
a = "tttt"
MsgBox (a)
End Sub
execute wrong
Option Explicit
Private Sub Command1_Click()
a = "tttt"
MsgBox (a)
End Sub
Set an object reference to a variable or property
Dim myForm As Form1
Set myForm = New Form1
myForm.show
Public Property Get shaperatio() As Long
    shaperatio = mlngshaperatio
End Property
dim a as new ClassA
msgbox a.shaperatio
single is 4 bytes,double is 8 bytes
single greatest accuracy can be expressed approximately six digit after decimal places
double greatest accuracy can be expressed approximately 14 digit decimal places

Public arrArgs  As Variant
Not be explicitly declared as other types of variable data types
public enum Season {
      winter, spring, summer, fall;
      private final static String location = "Phoenix";        
      public static Season getBest() {
            if (location.equals("Phoenix"))
                return winter;
            else
                return summer;
      }
}
On Error Resume Next
the code after this statement, if an error occur is not prompted to continue the statement 
following
Kill used to delete file
On Error GoTo 0
Ban any error handler in current procedure.
On Error Resume Next
continues to run after the error statement
On Error GoTo line
Startup error handler,start from the point line