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VB.NET:String

Trim removes leading and trailing whitespace. String data often has leading or trailing whitespace characters—newlines, spaces or tabs. These characters are usually not needed. With Trim we strip these characters in a declarative way.


Example. First, this code example references a string literal that contains leading spaces and a trailing space. Next the Trim Function is invoked, and a new string is allocated on the managed heap.

Tip: The string returned by the Trim Function does not contain the leading spaces or trailing space.

Next: To demonstrate, we print out the resulting value with square brackets denoting its first and last character positions.

VB.NET program that uses Trim function

Module Module1
    Sub Main()
	' Input string.
	Dim value As String = "  This is an example string. "
	' Invoke Trim function.
	value = value.Trim()
	' Write output.
	Console.Write("[")
	Console.Write(value)
	Console.WriteLine("]")
    End Sub
End Module

Output

[This is an example string.]

File lines. Text files that you process in your VB.NET program may have unnecessary spaces or tab characters. If you read in a file line-by-line (as with File.ReadAllLines) you can then trim these lines and process them with simpler logic.

VB.NET program that uses Trim on file lines

Imports System.IO

Module Module1
    Sub Main()
	' Read in the lines of a file.
	For Each line As String In File.ReadAllLines("data.txt")
	    ' The existing line.
	    Console.WriteLine("[{0}]", line)
	    ' Trimmed line.
	    Dim trimmed As String = line.Trim()
	    Console.WriteLine("[{0}]", trimmed)
	Next
    End Sub
End Module

Output

[  Something]
[Something]
[Example    ]
[Example]
[  Another]
[Another]

Dictionary. A popular use of the Dictionary constructed type in the VB.NET language is to store string keys and reference data objects as values. It is a good idea to trim input before passing it to a Dictionary lookup method.

Tip: This ensures that whitespace, which is typically not meaningful in this context, will not disrupt accurate lookups.

Dictionary

Summary. The Trim Function clears excess leading and trailing whitespace characters from string data. With Trim we more easily accept input from users and files. We can even look up keys in Dictionary or other data structure based on that input.