Use conditional statements to Control Program Execution
You can use conditional statements and cyclic statements to control the script process. You can use conditional statements to write VBScript code for judgment and repeated operations. The following conditions can be used in VBScript:
- If... Then... Else statement
- Select Case statement
Use If... Then... Else for judgment
If... Then... ElseStatement used to calculate whether the condition isTrueOrFalseAnd specify the statement to run based on the calculation result. Generally, the condition is an expression that uses a comparison operator to compare values or variables. For more information about comparison operators, see comparison operators.If... Then... ElseStatements can be nested as needed.
Run the statement when the condition is True.
If the condition isTrueRun a single row statement.If... Then... ElseStatement. The following example demonstrates the single line syntax. Note that the keyword is omitted in this example.Else.
Sub FixDate() Dim myDate myDate = #2/13/95# If myDate < Now Then myDate = Now End Sub
To run multi-line code, you must use the multi-line (or block) syntax. Multiline (or block) syntax includesEnd IfStatement:
Sub AlertUser(value) If value = 0 Then AlertLabel.ForeColor = vbRed AlertLabel.Font.Bold = True AlertLabel.Font.Italic = True End If End Sub
When the conditions are True and False, run some statements respectively.
AvailableIf... Then... ElseThe statement defines two executable statement blocks: the condition isTrueWhen a statement block is run, the condition isFalseRun another statement block.
Sub AlertUser(value) If value = 0 Then AlertLabel.ForeColor = vbRed AlertLabel.Font.Bold = True AlertLabel.Font.Italic = True Else AlertLabel.Forecolor = vbBlack AlertLabel.Font.Bold = False AlertLabel.Font.Italic = False End If End Sub
Judge multiple conditions
If... Then... ElseA type of statement deformation allows you to select from multiple conditions, that is, addElseIfClause to expandIf... Then... ElseThe statement function allows you to control program processes based on a variety of possibilities. For example:
Sub ReportValue(value) If value = 0 Then MsgBox value ElseIf value = 1 Then MsgBox value ElseIf value = 2 then Msgbox value Else Msgbox "
The value is out of the range!"
End If
You can add any numberElseIfClause to provide multiple options. Use multipleElseIfClause is often cumbersome. A better way to select multiple conditions is to useSelect CaseStatement.
Use Select Case for judgment
Select CaseStructure providesIf... Then... ElseIfA flexible structure. You can select to execute one of multiple statement blocks.Select CaseFunctions andIf... Then... ElseStatements are similar, but the code can be more concise and easy to read.
Select CaseThe structure uses a simple test expression that is only calculated once at the beginning. The result of the expression isCase. If yesCaseExample code:
Select Case Document.Form1.CardType.Options(SelectedIndex).Text Case "MasterCard" DisplayMCLogo ValidateMCAccount Case "Visa" DisplayVisaLogo ValidateVisaAccount Case "American Express" DisplayAMEXCOLogo ValidateAMEXCOAccount Case Else DisplayUnknownImage PromptAgainEnd Select
Note:Select CaseThe structure calculates only one expression at the beginning (only once), whileIf... Then... ElseIfStructure CalculationElseIfStatement expressions. These expressions can be different. Only when eachElseIfStatement calculation can only be used if the expressions are the sameSelect CaseStructure substitutionIf... Then... ElseIfStructure.