Expanding variables and subexpressions in strings

In PowerShell, you can define a string with single or double quotes. There is a difference between these two methods. In a single-quoted string, variables and subexpressions are not expanded, whereas, in a double-quoted string, they are expanded.

Let's look at an example of variable expansion in a double-quoted string:

PowerCLI C:\> $Number = 3
PowerCLI C:\> "The number is: $Number"
The number is: 3

In the preceding example, the string is defined with double quotes, and the $Number variable is expanded. Let's see what happens if you use single quotes:

PowerCLI C:\> $Number = 3
PowerCLI C:\> 'The number is: $Number'
The number is: $Number

Using a single-quoted string, PowerShell doesn't expand the $Number variable. Let's try to put the number of virtual CPUs of a virtual machine in a double-quoted string:

PowerCLI C:\> $vm = Get-VM -Name dc1
PowerCLI C:\> "The number of vCPU's of the vm is: $vm.NumCpu"
The number of vCPU's...