دستورات مرتبط با شرط‌هاوحلقه‌ها در VB

Loops and Conditional

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

If...Then...Else Statement
Conditionally executes a group of statements, depending on the value of an expression.
Syntax
If condition Then [statements] [Else elsestatements]
Or, you can use the block form syntax:
If condition Then
[statements]
[ElseIf condition-n Then
[elseifstatements] ...
[Else
[elsestatements]]
End If
The If...Then...Else statement syntax has these parts:
Part Description
condition Required. One or more of the following two types of expressions:
A numeric expression or string expression that evaluates to True or False.
If condition is Null, condition is treated as False.
An expression of the form TypeOf objectname Is objecttype. The
objectname is any object reference and objecttype is any valid object type.
The expression is True if objectname is of the object type specified by
objecttype; otherwise it is False.
statements Optional in block form; required in single-line form that has no Else clause.
One or more statements separated by colons; executed if condition is True.
condition-n Optional. Same as condition.
elseifstatements Optional. One or more statements executed if associated condition-n is
True.
elsestatements Optional. One or more statements executed if no previous condition or
condition-n expression is True.
Example:
Dim Number, Digits, MyString
Number = 53 ' Initialize variable.
If Number < 10 Then
Digits = 1
ElseIf Number < 100 Then
' Condition evaluates to True so the next statement is executed.
Digits = 2
Else
Digits = 3
End If

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

End Statements
Ends a procedure or block.
Syntax
End
End Function
End If
End Property
End Select
End Sub
Aaron Wirth
60
End Type
End With
The End statement syntax has these forms:
Statement Description
End Terminates execution immediately. Never required by itself but may be
placed anywhere in a procedure to end code execution, close files opened
with the Open statement and to clear variables.
End Function Required to end a Function statement.
End If Required to end a block If…Then…Else statement.
End Property Required to end a Property Let, Property Get, or Property Set procedure.
End Select Required to end a Select Case statement.
End Sub Required to end a Sub statement.
End Type Required to end a user-defined type definition (Type statement).
End With Required to end a With statement.
Remarks
When executed, the End statement resets all module-level variables and all static local variables in all
modules. To preserve the value of these variables, use the Stop statement instead. You can then resume
execution while preserving the value of those variables.
Example:
Sub Form_Load
Dim Password, Pword
PassWord = "Swordfish"
Pword = InputBox("Type in your password")
If Pword <> PassWord Then
MsgBox "Sorry, incorrect password"
End
End If
End Sub

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

Stop
Suspends execution.
Syntax
Stop
Remarks
You can place Stop statements anywhere in procedures to suspend execution. Using the Stop statement
is similar to setting a breahkpoint in the code.
The Stop statement suspends execution, but unlike End, it doesn't close any files or clear variables,
unless it is in a compiled executable (.exe) file.
Example:
If Label1 = “Blah” then
Stop
End if

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

Switch
Evaluates a list of expressions and returns a Variant value or an expression associated with the first
expression in the list that is True.
Syntax
Switch(expr-1, value-1[, expr-2, value-2 … [, expr-n,value-n]])
The Switch function syntax has these parts:
Part Description
expr Required. Variant expression you want to evaluate.
value Required. Value or expression to be returned if the corresponding
expression is True.
Remarks
The Switch function argument list consists of pairs of expressions and values. The expressions are
evaluated from left to right, and the value associated with the first expression to evaluate to True is
returned. If the parts aren't properly paired, a run-time error occurs. For example, if expr-1 is True,
Switch returns value-1. If expr-1 is False, but expr-2 is True, Switch returns value-2, and so on.
Switch returns a Null value if:
None of the expressions is True.
The first True expression has a corresponding value that is Null.
Example:
Function MatchUp (CityName As String)
Matchup = Switch(CityName = "London", "English", CityName _
= "Rome", "Italian", CityName = "Paris", "French")
End Function
‘This example uses the Switch function to return the name of a language that matches the name of a
city.

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

Goto
Branches unconditionally to a specified line within a procedure.
Syntax
GoTo line
The required line argument can be any line label or line number.
Remarks
GoTo can branch only to lines within the procedure where it appears.
Note Too many GoTo statements can make code difficult to read and debug. Use structured control
statements (Do...Loop, For...Next, If...Then...Else, Select Case) whenever possible.
Example:
If Label1 = “Blah” then
Goto Something
Else
End
Something:
End if

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

On...GoSub, On...GoTo Statements
Branch to one of several specified lines, depending on the value of an expression.
Syntax
On expression GoSub destinationlist
On expression GoTo destinationlist
The On...GoSub and On...GoTo statement syntax has these parts:
Part Description
expression Required. Any numeric expression that evaluates to a whole number
between 0 and 255, inclusive. If expression is any number other than a
whole number, it is rounded before it is evaluated.
destinationlist Required. List of line numbers or line labels separated by commas.
Remarks
The value of expression determines which line is branched to in destinationlist. If the value of
expression is less than 1 or greater than the number of items in the list, one of the following results
occurs:
If expression is Then
Equal to 0 Control drops to the statement following
On...GoSub or On...GoTo.
Greater than number of items in list Control drops to the statement following
On...GoSub or On...GoTo.
Negative An error occurs.
Greater than 255 An error occurs.
You can mix line numbers and line labels in the same list. You can use as many line labels and line
numbers as you like with On...GoSub and On...GoTo. However, if you use more labels or numbers
than fit on a single line, you must use the line-continuation character to continue the logical line onto
the next physical line.
GoSub...Return Statement
Branches to and returns from a subroutine within a procedure.
Syntax
GoSub line
...
line
...
Return
The line argument can be any line label or line number.
Remarks
You can use GoSub and Return anywhere in a procedure, but GoSub and the corresponding Return
statement must be in the same procedure. A subroutine can contain more than one Return statement,
but the first Return statement encountered causes the flow of execution to branch back to the statement
immediately following the most recently executed GoSub statement.
Note You can't enter or exit Sub procedures with GoSub...Return.
Example:
Sub GosubDemo()
Dim Num
' Solicit a number from the user.
Num = InputBox("Enter a positive number to be divided by 2.")
' Only use routine if user enters a positive number.
If Num > 0 Then GoSub MyRoutine
Debug.Print Num
Exit Sub ' Use Exit to prevent an error.
MyRoutine:
Num = Num/2 ' Perform the division.
Return ' Return control to statement.
End Sub ' following the GoSub statement.
With Statement
Executes a series of statements on a single object or a user-defined type.
Syntax

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

With object
[statements]
End With
The With statement syntax has these parts:
Part Description
object Required. Name of an object or a user-defined type.
statements Optional. One or more statements to be executed on object.
Remarks
The With statement allows you to perform a series of statements on a specified object without
requalifying the name of the object. For example, to change a number of different properties on a single
object, place the property assignment statements within the With control structure, referring to the
object once instead of referring to it with each property assignment. The following example illustrates
use of the With statement to assign values to several properties of the same object.
Example:
With MyLabel
.Height = 2000
.Width = 2000
.Caption = "This is MyLabel"
End With

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

For...Next Statement
Repeats a group of statements a specified number of times.
Syntax
For counter = start To end [Step step]
[statements]
[Exit For]
[statements]
Next [counter]
The For…Next statement syntax has these parts:
Part Description
counter Required. Numeric variable used as a loop counter. The variable can't be a
Boolean or an array element.
start Required. Initial value of counter.

end Required. Final value of counter.
step Optional. Amount counter is changed each time through the loop. If not
specified, step defaults to one.
statements Optional. One or more statements between For and Next that are executed
the specified number of times.
Remarks
The step argument can be either positive or negative. The value of the step argument determines loop
processing as follows:
Value Loop executes if
Positive or 0 counter <= end
Negative counter >= end
After all statements in the loop have executed, step is added to counter. At this point, either the
statements in the loop execute again (based on the same test that caused the loop to execute initially),
or the loop is exited and execution continues with the statement following the Next statement.
Example:
Dim Words, Chars, MyString
For Words = 10 To 1 Step -1 ' Set up 10 repetitions.
For Chars = 0 To 9 ' Set up 10 repetitions.
MyString = MyString & Chars ' Append number to string.
Next Chars ' Increment counter
MyString = MyString & " " ' Append a space.
Next Words

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

While...Wend Statement
Executes a series of statements as long as a given condition is True.
Syntax
While condition
[statements]
Wend
The While...Wend statement syntax has these parts:
Part Description
condition Required. Numeric expression or string expression that evaluates to True or
False. If condition is Null, condition is treated as False.
statements Optional. One or more statements executed while condition is True.
Remarks
If condition is True, all statements are executed until the Wend statement is encountered. Control then
returns to the While statement and condition is again checked. If condition is still True, the process is
repeated. If it is not True, execution resumes with the statement following the Wend statement.
While...Wend loops can be nested to any level. Each Wend matches the most recent While.
Tip The Do...Loop statement provides a more structured and flexible way to perform looping.
Example:
Dim Counter
Counter = 0 ' Initialize variable.
While Counter < 20 ' Test value of Counter.
Counter = Counter + 1 ' Increment Counter.
Wend ' End While loop when Counter > 19.
Debug.Print Counter ' Prints 20 in the Immediate window.

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

Do...Loop Statement
Repeats a block of statements while a condition is True or until a condition becomes True.
Syntax
Do [{While | Until} condition]
[statements]
[Exit Do]
[statements]
Loop
Or, you can use this syntax:
Do
[statements]
[Exit Do]
[statements]
Loop [{While | Until} condition]
The Do Loop statement syntax has these parts:
Part Description
condition Optional. Numeric expression or string expression that is True or False. If
condition is Null, condition is treated as False.
statements One or more statements that are repeated while, or until, condition is True.
Remarks
Any number of Exit Do statements may be placed anywhere in the Do…Loop as an alternate way to
exit a Do…Loop. Exit Do is often used after evaluating some condition, for example, If…Then, in
which case the Exit Do statement transfers control to the statement immediately following the Loop.
When used within nested Do…Loop statements, Exit Do transfers control to the loop that is one nested
level above the loop where Exit Do occurs.
Example:
Dim Check, Counter
Check = True: Counter = 0 ' Initialize variables.
Do ' Outer loop.
Do While Counter < 20 ' Inner loop.
Counter = Counter + 1 ' Increment Counter.
If Counter = 10 Then ' If condition is True.
Check = False ' Set value of flag to False.
Exit Do ' Exit inner loop.
End If
Loop
Loop Until Check = False ' Exit outer loop immediately.

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

IIF
Returns one of two parts, depending on the evaluation of an expression.
Syntax
IIf(expr, truepart, falsepart)
The IIf function syntax has these named arguments:
Part Description
expr Required. Expression you want to evaluate.
truepart Required. Value or expression returned if expr is True.
falsepart Required. Value or expression returned if expr is False.
Remarks
IIf always evaluates both truepart and falsepart, even though it returns only one of them. Because of
this, you should watch for undesirable side effects. For example, if evaluating falsepart results in a
division by zero error, an error occurs even if expr is True.
Example:
Function CheckIt (TestMe As Integer)
CheckIt = IIf(TestMe > 1000, "Large", "Small")
End Function
For Each...Next Statement
Repeats a group of statements for each element in an array or collection.
Syntax

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

For Each element In group
[statements]
[Exit For]
[statements]
Next [element]
The For...Each...Next statement syntax has these parts:
Part Description
element Required. Variable used to iterate through the elements of the collection or
array. For collections, element can only be a Variant variable, a generic
object variable, or any specific object variable. For arrays, element can only
be a Variant variable.
group Required. Name of an object collection or array (except an array of userdefined types).
statements Optional. One or more statements that are executed on each item in group.
Remarks
The For...Each block is entered if there is at least one element in group. Once the loop has been
entered, all the statements in the loop are executed for the first element in group. If there are more
elements in group, the statements in the loop continue to execute for each element. When there are no
more elements in group, the loop is exited and execution continues with the statement following the
Next statement.
Any number of Exit For statements may be placed anywhere in the loop as an alternative way to exit.
Exit For is often used after evaluating some condition, for example If…Then, and transfers control to
the statement immediately following Next.
Example:
Dim Found, MyObject, MyCollection
Found = False ' Initialize variable.
For Each MyObject In MyCollection ' Iterate through each element.
If MyObject.Text = "Hello" Then ' If Text equals "Hello".
Found = True ' Set Found to True.
Exit For ' Exit loop.
End If
Next

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دستور نوشتاری فرمان(Syntax) به نحو زیر است:

Select Case Statement
Executes one of several groups of statements, depending on the value of an expression.
Syntax
Select Case testexpression
[Case expressionlist-n
[statements-n]] ...
[Case Else
[elsestatements]]
End Select
The Select Case statement syntax has these parts:
Part Description
testexpression Required. Any numeric expression or string expression.
expressionlist-n Required if a Case appears. Delimited list of one or more of the following
forms: expression, expression To expression, Is comparisonoperator
expression. The To keyword specifies a range of values. If you use the To
keyword, the smaller value must appear before To. Use the Is keyword with
comparison operators (except Is and Like) to specify a range of values. If
not supplied, the Is keyword is automatically inserted.
statements-n Optional. One or more statements executed if testexpression matches any
part of expressionlist-n.
elsestatements Optional. One or more statements executed if testexpression doesn't match
any of the Case clause.
Remarks
If testexpression matches any Case expressionlist expression, the statements following that Case clause
are executed up to the next Case clause, or, for the last clause, up to End Select. Control then passes to
the statement following End Select. If testexpression matches an expressionlist expression in more
than one Case clause, only the statements following the first match are executed.
The Case Else clause is used to indicate the elsestatements to be executed if no match is found between
the testexpression and an expressionlist in any of the other Case selections. Although not required, it is
a good idea to have a Case Else statement in your Select Case block to handle unforeseen
testexpression values. If no Case expressionlist matches testexpression and there is no Case Else
statement, execution continues at the statement following End Select.
Example:
Dim Number
Number = 8 ' Initialize variable.
Select Case Number ' Evaluate Number.
Case 1 To 5 ' Number between 1 and 5, inclusive.
Debug.Print "Between 1 and 5"
' The following is the only Case clause that evaluates to True.
Case 6, 7, 8 ' Number between 6 and 8.
Debug.Print "Between 6 and 8"
Case 9 To 10 ' Number is 9 or 10.
Debug.Print "Greater than 8"
Case Else ' Other values.
Debug.Print "Not between 1 and 10"
End Select