DOTNET WORLD: Common String Operations .NET

Common String Operations in C# and VB.NET

All the samples are based on two pre-declared string variables: strOriginal and strModified.

string strOriginal = "These functions will come handy";

string strModified = String.Empty;

VB.NET

Dim strOriginal As String = "These functions will come handy"

Dim strModified As String = String.Empty

1. Iterate a String – You can use the ‘for’ loop or ‘foreach’ loop to iterate through a string. The ‘for’ loop gives you more flexibility over the iteration.

for (int i = 0; i < strOriginal.Length; i++)

{

MessageBox.Show(strOriginal[i].ToString());

}

foreach (char c in strOriginal)

{

MessageBox.Show(c.ToString());

}

VB.NET

For i As Integer = 0 To strOriginal.Length - 1

MessageBox.Show(strOriginal(i).ToString())

Next i

For Each c As Char In strOriginal

MessageBox.Show(c.ToString())

Next c

2. Split a String – You can split strings using String.Split(). The method takes an array of chars, representing characters to be used as delimiters. In this example, we will be splitting the strOriginal string using ‘space’ as delimiter.

char[] delim = {' '};

string[] strArr = strOriginal.Split(delim);

foreach (string s in strArr)

{

MessageBox.Show(s);

}

VB.NET

Dim delim As Char() = {" "c}

Dim strArr As String() = strOriginal.Split(delim)

For Each s As String In strArr

MessageBox.Show(s)

3. Extract SubStrings from a String – The String.Substring() retrieves a substring from a string starting from a specified character position. You can also specify the length.

// only starting position specified

strModified = strOriginal.Substring(25);

MessageBox.Show(strModified);

// starting position and length of string to be extracted specified

strModified = strOriginal.Substring(20, 3);

MessageBox.Show(strModified);

VB.NET

' only starting position specified

strModified = strOriginal.Substring(25)

MessageBox.Show(strModified)

' starting position and length of string to be extracted specified

strModified = strOriginal.Substring(20, 3)

MessageBox.Show(strModified)

4. Create a String array – There are different ways to create a Single Dimensional and Multi Dimensional String arrays. Let us explore some of them:

// Single Dimensional String Array

string[] strArr = new string[3] { "string 1", "string 2", "string 3"};

// Omit Size of Array

string[] strArr1 = new string[] { "string 1", "string 2", "string 3" };

// Omit new keyword

string[] strArr2 = {"string 1", "string 2", "string 3"};

// Multi Dimensional String Array

string[,] strArr3 = new string[2, 2] { { "string 1", "string 2" }, { "string 3", "string 4" } };

// Omit Size of Array

string[,] strArr4 = new string[,] { { "string 1", "string 2" }, { "string 3", "string 4" } };

// Omit new keyword

string[,] strArr5 = { { "string 1", "string 2" }, { "string 3", "string 4" } };

VB.NET

' Single Dimensional String Array

Dim strArr As String() = New String(2) { "string 1", "string 2", "string 3"}

' Omit Size of Array

Dim strArr1 As String() = New String() { "string 1", "string 2", "string 3" }

' Omit new keyword

Dim strArr2 As String() = {"string 1", "string 2", "string 3"}

' Multi Dimensional String Array

Dim strArr3 As String(,) = New String(1, 1) { { "string 1", "string 2" }, { "string 3", "string 4" } }

' Omit Size of Array

Dim strArr4 As String(,) = New String(, ) { { "string 1", "string 2" }, { "string 3", "string 4" } }

' Omit new keyword

Dim strArr5 As String(,) = { { "string 1", "string 2" }, { "string 3", "string 4" } }

5. Reverse a String – One of the simplest ways to reverse a string is to use the StrReverse() function. To use it in C#, you need to add a reference to the Microsoft.VisualBasic dll.

string strModified = Microsoft.VisualBasic.Strings.StrReverse(strOriginal);

MessageBox.Show(strModified);

VB.NET

Dim strModified As String = StrReverse(strOriginal)

MsgBox(strModified)

6. Compare Two Strings – You can use the String.Compare() to compare two strings. The third parameter is a Boolean parameter that determines if the search is case sensitive(false) or not(true).

if ((string.Compare(strOriginal, strModified, false)) < 0)

{

MessageBox.Show("strOriginal is less than strOriginal1");

}

else if ((string.Compare(strOriginal, strModified, false)) > 0)

{

MessageBox.Show("strOriginal is more than strOriginal1");

}

else if ((string.Compare(strOriginal, strModified, false)) == 0)

{

MessageBox.Show("Both strings are equal");

}

VB.NET

If (String.Compare(strOriginal, strModified, False)) < 0 Then

MessageBox.Show("strOriginal is less than strOriginal1")

ElseIf (String.Compare(strOriginal, strModified, False)) > 0 Then

MessageBox.Show("strOriginal is more than strOriginal1")

ElseIf (String.Compare(strOriginal, strModified, False)) = 0 Then

MessageBox.Show("Both strings are equal")

End If

7. Convert a String to Byte[] (Byte Array) – The Encoding.GetBytes() encodes all the characters into a sequence of bytes. The method contains six overloads out of which we will be using the Encoding.GetBytes(String).

byte[] b = Encoding.Unicode.GetBytes(strOriginal);

VB.NET

Dim b As Byte() = Encoding.Unicode.GetBytes(strOriginal)

Note: You can adopt different character encoding schemes (ASCII, Unicode etc.) based on your requirement.

8. Convert Byte[] to String – The Encoding.GetString() decodes a sequence of bytes into a string.

// Assuming you have a Byte Array byte[] b

strModified = Encoding.Unicode.GetString(b);

VB.NET

' Assuming you have a Byte Array byte[] b

strModified = Encoding.Unicode.GetString(b)

9. Convert a String to Char[](Char Array) – To convert a String to Char Array, use the String.ToCharArray() which copies the characters in the string to a Unicode character array.

char[] chArr = strOriginal.ToCharArray();

VB.NET

Dim chArr As Char() = strOriginal.ToCharArray()

10. Convert a Char[] to String – A convenient way to convert a character array to string is to use the String constructor which accepts a character array

strModified = new String(chArr);

VB.NET

strModified = New String(chArr)

11. Test if String is null or Zero Length – A simple way to test if a string is null or empty is to use the String.IsNullOrEmpty(string) which returns a Boolean value.

bool check = String.IsNullOrEmpty(strOriginal);

VB.NET

Dim check As Boolean = String.IsNullOrEmpty(strOriginal)

Create a String of characters accepted from user -

12. Convert the Case of a String – The String class contains methods to convert a string to lower and upper cases. However, it lacks a method to convert a string to Proper Case/Title Case. Hence we will use the ‘TextInfo’ class to do the same.

System.Globalization.CultureInfo cultureInfo = System.Threading.Thread.CurrentThread.CurrentCulture;

System.Globalization.TextInfo textInfo = cultureInfo.TextInfo;

// Lower Case

MessageBox.Show(textInfo.ToLower(strOriginal));

// Upper Case

MessageBox.Show(textInfo.ToUpper(strOriginal));

// Proper Case

MessageBox.Show(textInfo.ToTitleCase(strOriginal));

VB.NET

Dim cultureInfo As System.Globalization.CultureInfo = System.Threading.Thread.CurrentThread.CurrentCulture

Dim textInfo As System.Globalization.TextInfo = cultureInfo.TextInfo

' Lower Case

MessageBox.Show(textInfo.ToLower(strOriginal))

' Upper Case

MessageBox.Show(textInfo.ToUpper(strOriginal))

' Proper Case

MessageBox.Show(textInfo.ToTitleCase(strOriginal))

13. Count the occurrences of words in a String – You can adopt multiple ways to find the occurrence of a word in a string. One of them is to use the String.IndexOf() which is one of the ways of finding the occurrence of the word. In VB.NET, use String.InStr().

Another simple way is to use ‘Count’ property of the Regex.Matches() collection. However this method is slow. We will explore both these methods in the sample.

// Using IndexOf

int strt = 0;

int cnt = -1;

int idx = -1;

strOriginal = "She sells sea shells on the sea shore";

string srchString = "sea";

while (strt != -1)

{

strt = strOriginal.IndexOf(srchString, idx + 1);

cnt += 1;

idx = strt;

}

MessageBox.Show(srchString + " occurs " + cnt + " times");

// Using Regular Expression

System.Text.RegularExpressions.Regex rex = new System.Text.RegularExpressions.Regex(srchString);

int count = rex.Matches(strOriginal).Count;

MessageBox.Show(srchString + " occurs " + count + " times");

VB.NET

' Using IndexOf

Dim strt As Integer = 0

Dim cnt As Integer = -1

Dim idx As Integer = -1

strOriginal = "She sells sea shells on the sea shore"

Dim srchString As String = "sea"

Do While strt <> -1

strt = strOriginal.IndexOf(srchString, idx + 1)

cnt += 1

idx = strt

Loop

MessageBox.Show(srchString & " occurs " & cnt & " times")

' Using Regular Expression

Dim rex As System.Text.RegularExpressions.Regex = New System.Text.RegularExpressions.Regex(srchString)

Dim count As Integer = rex.Matches(strOriginal).Count

MessageBox.Show(srchString & " occurs " & count & " times")

14. Insert Characters inside a String – The String.Insert() inserts text at a specified index location of a string. You can insert either a character or a string at a given index location. For eg: We will insert a string “very” at index 26 in string strOriginal.

strModified = strOriginal.Insert(26, "very ");

MessageBox.Show(strModified);

VB.NET

strModified = strOriginal.Insert(26, "very ")

MessageBox.Show(strModified)

15. Replace characters in a String – The String.Replace() removes characters from a string and replaces them with a new character or string.

strModified = strOriginal.Replace("come handy", "be useful");

MessageBox.Show(strModified);

VB.NET

strModified = strOriginal.Replace("come handy", "be useful")

MessageBox.Show(strModified)

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

// Count words

System.Text.RegularExpressions.MatchCollection wordColl = System.Text.RegularExpressions.Regex.Matches(strOriginal, @"[\S]+");

MessageBox.Show(wordColl.Count.ToString());

// Count characters. White space is treated as a character

System.Text.RegularExpressions.MatchCollection charColl = System.Text.RegularExpressions.Regex.Matches(strOriginal, @".");

MessageBox.Show(charColl.Count.ToString());

VB.NET

' 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);

// Removes specified number of characters(five) starting at index 20

strModified = strOriginal.Remove(20,5);

MessageBox.Show(strModified);

VB.NET

' Removes everything beginning at index 25

strModified = strOriginal.Remove(25)

MessageBox.Show(strModified)

' 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 = "8/20/2008";

DateTime dt = DateTime.Parse(strOriginal);

VB.NET

strOriginal = "8/20/2008"

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

byte[] byt = System.Text.Encoding.UTF8.GetBytes(strOriginal);

// convert the byte array to a Base64 string

strModified = Convert.ToBase64String(byt);

VB.NET

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();

byte[] b = Convert.FromBase64String(strModified);

strOriginal = System.Text.Encoding.UTF8.GetString(b);

VB.NET

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);

VB.NET

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("#"));

VB.NET

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,'*');

VB.NET

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

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

string[] strArr = new string[3] { "str1", "str2", "str3"};

string strModified = string.Join(";", strArr);

VB.NET

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";

int temp = Int32.Parse(strOriginal);

VB.NET

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");

VB.NET

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);

VB.NET

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

The String.Format() contains 5 overloads which can be studied over here

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.

int i = 0;

strOriginal = "234abc";

bool b = Int32.TryParse(strOriginal, out i);

VB.NET

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))

MessageBox.Show("true");

VB.NET

If strOriginal.StartsWith("THese",StringComparison.CurrentCultureIgnoreCase) Then

MessageBox.Show("true")

End If

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Tuesday, October 19, 2010

Common String Operations .NET

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