Conditionally executes a group of statements, depending on the value of an expression.
If condition [ Then ] [ statements ] [ ElseIf elseifcondition [ Then ] [ elseifstatements ] ] [ Else [ elsestatements ] ] End If
If condition Then [ statements ] [ Else elsestatements ]
- Required. Expression. The expression you supply for condition must evaluate to True or False, or to a data type that is implicitly convertible to Boolean.
- Optional in multiple-line form; required in single-line form that has no Else clause. One or more statements following If...Then that are executed if condition is True.
- Required if ElseIf is present. Same as condition.
- Optional. One or more statements following ElseIf...Then that are executed if the associated elseifcondition is True.
- Optional in multiple-line form; required in single-line form that has an Else clause. One or more statements that are executed if no previous condition or elseifcondition expression is True.
- End If
- Terminates If...Then block.
You can use the single-line form for short, simple tests. However, the multiple-line form provides more structure and flexibility than the single-line form and is usually easier to read, maintain, and debug.
With the single-line form, it is possible to have multiple statements executed as the result of an If...Then decision. All statements must be on the same line and be separated by colons, as in the following example:
If A > 10 Then A = A + 1 : B = B + A : C = C + B
In the multiple-line form, the If statement must be the only statement on the first line. The Else, ElseIf, and End If statements can be preceded only by a line label. The multiple-line If...Then...Else must end with an End If statement.
To determine whether or not an If statement introduces a multiple-line form, examine what follows the Then keyword. If anything other than a comment appears after Then in the same statement, the statement is treated as a single-line If statement. If Then is absent, it must be the beginning of a multiple-line If...Then...Else.
The ElseIf and Else clauses are both optional. You can have as many ElseIf clauses as you want in a multiple-line If...Then...Else, but none can appear after an Else clause. Multiple-line forms can be nested within one another.
When a multiple-line If...Then...Else is encountered, condition is tested. If condition is True, the statements following Then are executed. If condition is False, each ElseIf statement is evaluated in order. When a True elseifcondition is found, the statements immediately following the associated Then are executed. If no elseifcondition evaluates to True, or if there are no ElseIf statements, the statements following Else are executed. After executing the statements following Then, ElseIf, or Else, execution continues with the statement following End If.
Tip Select Case might be more useful when evaluating a single expression that has several possible values.
This example shows both the multiple- and single-line forms of the If...Then...Else statement.
Dim Number, Digits As Integer Dim MyString As String 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 ' Assign a value using the single-line form of syntax. If Digits = 1 Then MyString = "One" Else MyString = "More than one"
Use the TypeOf keyword to determine whether the Control object passed into a procedure is a text box.
Sub ControlProcessor(ByVal MyControl As Control) If TypeOf MyControl Is ComboBox Then Debug.WriteLine ("You passed in a " & TypeName(MyControl)) ElseIf TypeOf MyControl Is CheckBox Then Debug.WriteLine ("You passed in a " & TypeName(MyControl)) ElseIf TypeOf MyControl Is TextBox Then Debug.WriteLine ("You passed in a " & TypeName(MyControl)) End If End Sub