ElseIf is a method for doing cascading comparisons. This is best used when you have a series of conditions, and you want to take an action for the first true condition, or a single action if the are all false.
The syntax for ElseIf is:
If <condition> Then
<code to execute>
ElseIf <condition> Then
<code to execute>
Else
<code to execute>
End If
You may have as many ElseIf's as you want.
Example 1: You have a simple calculator that adds two numbers. You want to make sure that the user enter something in both boxes before you do any addition.
If txtNumber1.Text = "" Then
MsgBox "Please Enter Number 1"
ElseIf txtNumber2.Text = "" Then
MsgBox "Please Enter Number 2"
Else
'Code to add the numbers
End If
Example 2: You want to display the appropriate letter grade, given a number grade.
If (intGrade > 90) Then
lblGrade.Caption = "A"
ElseIf (intGrade > 80) Then
lblGrade.Caption = "B"
ElseIf (intGrade > 70) Then
lblGrade.Caption = "C"
ElseIf (intGrade > 60) Then
lblGrade.Caption = "D"
Else
lblGrade.Caption = "F"
End If
Example 2 clearly shows the cascading effect of a series of ElseIf's.