DevTut

# Conditional statements

# The If statement

The If control statement allows different code to be executed depending upon the evaluation of a conditional (Boolean) statement. A conditional statement is one that evaluates to either True or False, e.g. x > 2.

There are three patterns that can be used when implementing an If statement, which are described below. Note that an If conditional evaluation is always followed by a Then.

1. Evaluating one If conditional statement and doing something if it is True

Single line If statement

This is the shortest way to use an If and it is useful when only one statement needs to be carried out upon a True evaluation. When using this syntax, all of the code must be on a single line. Do not include an End If at the end of the line.

If [Some condition is True] Then [Do something]

If block

If multiple lines of code need to be executed upon a True evaluation, an If block may be used.

If [Some condition is True] Then
  [Do some things]
End If

Note that, if a multi-line If block is used, a corresponding End If is required.

2. Evaluating one conditional If statement, doing one thing if it is True and doing something else if it is False

Single line If, Else statement

This may be used if one statement is to be carried out upon a True evaluation and a different statement is to be carried out on a False evaluation. Be careful using this syntax, as it is often less clear to readers that there is an Else statement. When using this syntax, all of the code must be on a single line. Do not include an End If at the end of the line.

If [Some condition is True] Then [Do something] Else [Do something else]

If, Else block

Use an If, Else block to add clarity to your code, or if multiple lines of code need to be executed under either a True or a False evaluation.

If [Some condition is True] Then
   [Do some things]
Else
   [Do some other things]
End If

Note that, if a multi-line If block is used, a corresponding End If is required.

3. Evaluating many conditional statements, when preceding statements are all False, and doing something different for each one

This pattern is the most general use of If and would be used when there are many non-overlapping conditions that require different treatment. Unlike the first two patterns, this case requires the use of an If block, even if only one line of code will be executed for each condition.

If, ElseIf, ..., Else block

Instead of having to create many If blocks one below another, an ElseIf may be used evaluate an extra condition. The ElseIf is only evaluated if any preceding If evaluation is False.

If [Some condition is True] Then
   [Do some thing(s)]
ElseIf [Some other condition is True] Then
   [Do some different thing(s)]
Else    'Everything above has evaluated to False
   [Do some other thing(s)]
End If

As many ElseIf control statements may be included between an If and an End If as required. An Else control statement is not required when using ElseIf (although it is recommended), but if it is included, it must be the final control statement before the End If.

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