Visual Basic.NET How to Program (PDF)

638 Strings, Characters and Regular Expressions Chapter 15
31
32 ' copy characters from string1 into characterArray
33 string1.CopyTo(0, characterArray, 0, 5)
34 output &= vbCrLf & "The character array is: "
35
36 For i = 0 To characterArray.GetUpperBound(0)
37 output &= characterArray(i)
38 Next
39
40 MessageBox.Show(output, "Demonstrating String" & _
41 " properties Length and Chars", _
42 MessageBoxButtons.OK, MessageBoxIcon.Information)
43 End Sub ' Main
44
45 End Module ' modMiscellaneous
Fig. 15.2 String Length and Chars properties, and CopyTo method (part 2
of 2).
In this example, we create an application that determines the length of a String,
reverses the order of the characters in the String and copies a series of characters from
the String into a character array.
Line 22 uses String property Length to determine the number of characters in
String string1. Like arrays, Strings always know their own size.
Lines 28–30 append to output the characters of the String string1 in reverse
order. The String property Chars returns the character located in a specific index in the
String. Property Chars takes an Integer argument specifying the index and returns
the character at that index. As in arrays, the first element of a String is at index 0.
Common Programming Error 15.1
Attempting to access a character that is outside the bounds of a String (i.e., an index less
than 0 or an index greater than or equal to the String’s length) results in an Index-
OutOfRangeException. 15.1
Line 33 uses String method CopyTo to copy the characters of a String
(string1) into a character array (characterArray). The first argument given to
method CopyTo is the index from which the method begins copying characters in the
String. The second argument is the character array into which the characters are copied.
The third argument is the index specifying the location at which the method places the
copied characters in the character array. The last argument is the number of characters that
the method will copy from the String. Lines 36–38 append the Char array contents to
String output one character at a time.