String LengthHow many characters are contained in your VB.NET String? With the Length property on the String type, you can determine this count fast.
Length is useful in many programs. Its implementation is also interesting to examine. We explore the performance accessing Length in a for-loop.
We see the Length property inaction. The length of the String "dotnet" is found to be 6 characters. After another 5 characters are appended, the length is now 11 characters.
String cannot be directly changed. So when "perls" is appended to the String, a whole new String is created.String creation, the length value is stored. The String will thus always have the same length.Module Module1
Sub Main()
' Get length of string.
Dim value As String = "dotnet"
Dim length As Integer = value.Length
Console.WriteLine("{0}={1}", value, length)
' Append a string.
' ... Then get the length of the newly-created string.
value += "perls"
length = value.Length
Console.WriteLine("{0}={1}", value, length)
End Sub
End Moduledotnet=6
dotnetperls=11For-loopThe Length of a string is often used in a For-loop in VB.NET programs. Each character can be tested or handled, one-by-one.
Module Module1
Sub Main()
Dim animal as String = "bird"
' Loop until length minus 1.
For i as Integer = 0 To animal.Length - 1
Console.WriteLine(animal(i))
Next
End Sub
End Moduleb
i
r
dA String's length could be computed once and stored as a field. Or it could be calculated in a loop every time the property is accessed.
string equally fast.Length were to be computed each time, a loop over every character that tested against the bound Length would be slow.The Length is computed whenever a String is created. When you access Length, characters are not counted: instead the cached value is returned.
We examined Length from a conceptual perspective. Dynamically computing the Length could cause a performance nightmare. But this is not a problem in VB.NET.