String Operations in VB.NET (Part II)

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Visual Basic.NET is the most recent generation of Visual Basic. Developers will be pleased to note that its new features include inheritance, method overloading, structured exception handling, and more. These capabilities make it easier than ever to create .NET applications, including Windows applications, web services, and web applications. The articles in this section give you all the tips you need to work wit this useful language.

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TOPIC: String Operations in VB.NET (Part II)

String Operations in VB.NET (Part II) 03 May 2010 21:48 #372

Introduction
In the previous article, 30 Common String Operations in VB.NET (Part I)
, we explored 15 common String operations while working with the String class. In Part

II of the article, we will continue with the series and cover 15 more.
All the samples are based on two pre-declared string variables: strOriginal and strModified.

Dim strOriginal As String = "These functions will come handy"
    Dim strModified As String = String.Empty

16. Count Words and Characters In a String
You can use Regular Expression to do so as shown below:

       ' Count words
      Dim wordColl As System.Text.RegularExpressions.MatchCollection = 
 
System.Text.RegularExpressions.Regex.Matches(strOriginal, "[\S]+")
      MessageBox.Show(wordColl.Count.ToString())
      ' Count characters. White space is treated as a character
      Dim charColl As System.Text.RegularExpressions.MatchCollection = 
 
System.Text.RegularExpressions.Regex.Matches(strOriginal, ".")
      MessageBox.Show(charColl.Count.ToString())

17. Remove characters in a String
The String.Remove() deletes a specified number of characters beginning at a given location

within a string

 ' Removes everything beginning at index 25
      strModified = strOriginal.Remove(25)
      MessageBox.Show(strModified)
 
Or
      ' Removes specified number of characters(five) starting at index 20
      strModified = strOriginal.Remove(20,5)
      MessageBox.Show(strModified)

18. Create Date and Time from String
Use the DateTime.Parse() to convert a string representing datetime to its DateTime

equivalent. The DateTime.Parse() provides flexibility in terms of adapting strings in various

formats.

 strOriginal = "03/05/2010"
      Dim dt As DateTime = DateTime.Parse(strOriginal)

19. Convert String to Base64
You will have to use the methods in System.Text.Encoding to convert string to Base64. The

conversion involves two processes:

a. Convert string to a byte array b. Use the Convert.ToBase64String() method to convert the byte array to a Base64 string

    Dim byt As Byte() = System.Text.Encoding.UTF8.GetBytes(strOriginal)
      ' convert the byte array to a Base64 string
      strModified = Convert.ToBase64String(byt)

20. Convert Base64 string to Original String
In the previous example, we converted a string ‘strOriginal’ to Base64 string ‘strModified’. In

order to convert a Base64 string back to the original string, use FromBase64String(). The

conversion involves two processes:

a. The FromBase64String() converts the string to a byte array b. Use the relevant Encoding method to convert the byte array to a string, in our case UTF8.GetString();

 Dim b As Byte() = Convert.FromBase64String(strModified)
      strOriginal = System.Text.Encoding.UTF8.GetString(b)

21. How to Copy a String
A simple way to copy a string to another is to use the String.Copy(). It works similar to

assigning a string to another using the ‘=’ operator.

 strModified = String.Copy(strOriginal

22. Trimming a String
The String.Trim() provides two overloads to remove leading and trailing spaces as well as to

remove any unwanted character. Here’s a sample demonstrating the two overloads. Apart

from trimming the string, it also removes the "#" character.

    strOriginal = " Some new string we test ##"
      strModified = strOriginal.Trim().Trim(Char.Parse("#"))

23. Padding a String
The String.PadLeft() or PadRight() pads the string with a character for a given length. The

following sample pads the string on the left with 3 *(stars). If nothing is specified, it adds

spaces.

strModified = strOriginal.PadLeft(34,"*"c)

24. Create a Delimited String
To create a delimited string out of a string array, use the String.Join()

  Dim strArr As String() = New String(2) { "str1", "str2", "str3"}
      Dim strModified As String = String.Join(";", strArr)

25. Convert String To Integer
In order to convert string to integer, use the Int32.Parse(). The Parse method converts the

string representation of a number to its 32-bit signed integer equivalent. If the string

contains non-numeric values, it throws an error.
Similarly, you can also convert string to other types using Boolean.Parse(), Double.Parse(),

char.Parse() and so on.

 strOriginal = "12345"
      Dim temp As Integer = Int32.Parse(strOriginal)

26. Search a String

You can use

IndexOf, LastIndexOf,

StartsWith, and EndsWith to search a string.
27. Concatenate multiple Strings
To concatenate string variables, you can use the ‘+’ or ‘+=’ operators. You can also use the

String.Concat() or String.Format().

strModified = strOriginal & "12345"
      strModified = String.Concat(strOriginal, "abcd")
      strModified = String.Format("{0}{1}", strOriginal, "xyz")

However, when performance is important, you should always use the StringBuilder class to

concatenate strings.
28. Format a String
The String.Format() enables the string’s content to be determined dynamically at runtime. It

accepts placeholders in braces {} whose content is replaced dynamically at runtime as shown

below:

 strModified = String.Format("{0} - is the original string",strOriginal)

29. Determine If String Contains Numeric value
To determine if a String contains numeric value, use the Int32.TryParse() method. If the

operation is successful, true is returned, else the operation returns a false.

Dim i As Integer = 0
      strOriginal = "234abc"
      Dim b As Boolean = Int32.TryParse(strOriginal, i)

Note: TryParse also returns false if the numeric value is too large for the type that’s

receiving the result.

30. Determine if a String instance starts with a specific string
Use the StartsWith() to determine whether the beginning of a string matches some specified

string. The method contains 3 overloads which also contains options to ignore case while

checking the string.

      If strOriginal.StartsWith("THese",StringComparison.CurrentCultureIgnoreCase) 
 
Then
            MessageBox.Show("true")
      End If

So those were some 30 common string operations that we saw in these two articles. Since

these articles contained only a short introduction of each method, I would suggest you to

explore each method in detail using the MSDN documentation. Mastering string operations

can save us a lot of time in projects and improve application performance too. I hope this

article was useful and I thank you for viewing it.
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