Control-Flow

PowerShell provides a comprehensive set of flow-control constructs, starting with if/elseif/else as follows:

$Value = 2
If ($Value -eq 1) {
Do-Something
}
ElseIf ($Value -eq 2) {
Do-SomethingElse
}
Else {
Do-SomethingCompletelyDifferent
}

Note that we have a completely different set of comparison and logical operators to remember as follows:

Equals	-eq
Not Equal To	-ne
Greater Than	-gt
Greater Than or Equal To	-ge
Less Than	-lt
Less Than or Equal To	-le
Not	-not or !
And	-and
Or	-or

Additionally, if you're doing string comparison, you can force case-sensitive or case-insensitive (default comparison is case-insensitive) by prefacing the operator with a c or i e.g. -ceq is a case-sensitive equal comparison.

In addition to the if flow control, PowerShell also has:

• Do While - Do {Code Block} While (Condition)
• While - While (Condition) {Code Block}
• Do Until -
• For - For ($Index = 1; $Index -le 3; $Index++) {Code Block}
• ForEach - ForEach ($MyObject In $MyObjectsArrayOrCollection) {Code Block}
• Switch -
  

  Switch ($MyValue)
  {
      Result1 {Code Block}
      Result2 {Code Block}
      Default {Code Block}
  }

A couple of good articles on flow control are:

• PowerShell Tutorial 8: Conditional Logic (if, elseif, else, and switch)
• PowerShell Tutorial 9: Getting Loopy