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This article introduces the knowledge of "how to use conditional statements in VBScript". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Control program execution

Conditional statements and loop statements can be used to control the flow of Script. Conditional statements can be used to write VBScript code that makes judgments and repeats operations. The following conditional statements can be used in VBScript:

If...Then...Else statement

Select Case statement

Use If...Then...Else to judge

The If...Then...Else statement is used to evaluate whether the condition is True or False and to specify the statement to run based on the result of the calculation. Typically, the condition is an expression that uses a comparison operator to compare a value or variable. For more information about comparison operators, see comparison operators. If...Then...Else statements can be nested as needed.

Run the statement when the condition is True

To run a single-line statement when the condition is True, use the single-line syntax of the If...Then...Else statement. The following example demonstrates one-line syntax. Note that the keyword Else is omitted in this example.

Sub FixDate ()

Dim myDate

MyDate = # 2Compact 13Compact 9pm

If myDate < Now Then myDate = Now

End Sub

To run multiple lines of code, you must use multiline (or block) syntax. The multiline (or block) syntax contains End If statements, as follows:

Sub AlertUser (value)

If value = 0 Then

AlertLabel.ForeColor = vbRed

AlertLabel.Font.Bold = True

AlertLabel.Font.Italic = True

End If

End Sub

Run certain statements when the condition is True and False

You can define two executable statement blocks using the If...Then...Else statement: one statement block is run when the condition is True, and another statement block is run when the condition is False.

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

A variant of the If...Then...Else statement allows you to choose from multiple conditions, that is, adding an ElseIf clause to extend the functionality of the If...Then...Else statement, allowing you to control based on a variety of possible program flows. 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 "value is out of range!"

End If

You can add as many ElseIf clauses as you want to provide multiple choices. Using multiple ElseIf clauses can often become cumbersome. A better way to choose among multiple conditions is to use the select Case statement.

Use select Case to judge

The select Case structure provides a workaround of the If...Then...ElseIf structure, and you can choose to execute one of multiple statement blocks. Select Case statements provide functions similar to If...Then...Else statements, but can make the code more concise and readable.

The select Case structure uses a simple test expression that evaluates only once at the beginning of it. The result of the expression is compared to the value of each Case in the structure. If there is a match, the block of statements associated with the Case is executed:

Select Case Document.Form1.CardType.Options (selectedIndex). Text

Case "MasterCard"

DisplayMCLogo

ValidateMCAccount

Case "Visa"

DisplayVisaLogo

ValidateVisaAccount

Case "American Express"

DisplayAMEXCOLogo

ValidateAMEXCOAccount

Case Else

DisplayUnknownImage

PromptAgain

End select

Note that the select Case structure evaluates only one expression at the beginning (only once), while the If...Then...ElseIf structure evaluates the expression of each ElseIf statement, which can vary. You can use the select Case structure instead of the If...Then...ElseIf structure only if each ElseIf statement evaluates the same expression.

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