PowerShell treats all strings
as System.String objects.
This means that you can use the
rich set of methods and properties
available to those objects.
As shown Lesson 3, the Get-
Member cmdlet retrieves an
object’s members as the object
is passed down the pipeline.
Because a string is passed down
as an object, you can use Get-
Member for that string. For example, the following statement
retrieves the object members for the string test output:
“test output” | Get-Member
As you can see in Figure A, a string object supports numerous
methods, including Substring and GetType. If you were to scroll
down, you would also find the Length property, which provides
the number of characters in the string.
Now suppose you want to learn more about the Substring
method of the System.String object. You can again use Get-
Member to retrieve the information you need. You specify the
Substring method as an argument to Get-Member, then pipeline
the results to the Format-List cmdlet:
“test output” |
Get-Member Substring |
Format-List
Figure B shows the statement’s result. Notice that the definition
includes details about how to use the method. This is the method’s
syntax. The syntax specifies that you can choose one of two
approaches when calling this method. Those approaches are:
System.String Substring(Int32 startIndex)
System.String Substring(Int32 startIndex, Int32 length)
In the first approach, you provide the target string and an integer
that specifies the position in which you want the substring to start.
The method will then return a substring that begins at this position
and ends at the end of the string. For example, if the target string is
test output and you want to return a substring that starts at position
5, you’d use the statement
(“test output”).Substring(5)
which would return the substring output. As this statement shows, you
must enclose the target string in parentheses, then add a period followed
by the method name and the parameter enclosed in parentheses.
In the second approach, you provide the target string and the
substring’s starting position and length. For example, suppose you
want to return a substring that starts at the beginning of the string
(position 0) and is four characters long. You’d use the statement
(“test output”).Substring(0,4)
which would return the substring test.
When you call a method such as Substring or GetType, it generates
its own object that can be passed down the pipeline. As a result,
you can use Get-Member to retrieve a list of those object’s members.
For example, the GetType method returns a System.RuntimeType
object, and that object supports numerous methods and properties.
The following statement returns a list of properties available to the
System.RuntimeType object:
(“test output”).GetType() |
Get-Member -MemberType Property
As the statement shows, you first enclose the string in parentheses,
add a period followed by the method name, which in this case is Get-
Type. You then pipe the object returned by GetType to Get-Member.
Notice that I’ve used the -MemberType parameter to display only the
returned object’s properties. Figure C shows the results.
End of Article
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