Computer Programming || Chapter 3: String manipulation

Connect applications with DBMS Streams-Based Sockets and Datagrams Syllabus www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra Revision of OOP Exception Handling String manipulation Regular expression Files and Streams Connect applications with DBMS Streams-Based Sockets and Datagrams

Contents string vs. System.String Immutability of String Objects www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra string vs. System.String Immutability of String Objects Substrings and Split string with delimiter Trim Function Strip specified number of characters from string Tour with C# String Variables Practice

string vs. System.String www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra A string is an object of type String whose value is text. Internally, the text is stored as a sequential read-only collection of Char objects. The Length property of a string represents the number of Char objects it contains.

Immutability of String Objects www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra String objects are immutable; they cannot be changed after they have been created. All of the String methods and C# operators that appear to modify a string actually return the results in a new string object.

Immutability of String Objects www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra In the following example, when the contents of s1 and s2 are concatenated to form a single string, the two original strings are unmodified. The += operator creates a new string that contains the combined contents.

Immutability of String Objects www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra That new object is assigned to the variable s1, and the original object that was assigned to s1 is released for garbage collection because no other variable holds a reference to it.

Substrings www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra A substring is any sequence of characters that is contained in a string. Use the Substring method to create a new string from a part of the original string. You can search for one or more occurrences of a substring by using the IndexOf method.

Substrings www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra Use the Replace method to replace all occurrences of a specified substring with a new string. Like the Substring method, Replace actually returns a new string and does not modify the original string.

Example: Substrings String input = textBox1.Text; www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra String input = textBox1.Text; MessageBox.Show("number of characters is: "+ input.Length); String input = textBox1.Text; int beging = Convert.ToInt16(textBox2.Text); int count = Convert.ToInt16(textBox3.Text); MessageBox.Show("The Sub string is: " + input.Substring(beging, count)); String input = textBox1.Text; String find = textBox4.Text; string rep = textBox5.Text; MessageBox.Show("The Sub string after replacement is: " + input.Replace(find, rep)); String input = textBox1.Text; String str = textBox7.Text; MessageBox.Show("The index of Sub string is: " + input.IndexOf(str));

Split string with delimiter www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra The example below shows how to split the string into separate parts via a specified delimiter. The results get put into the Split array and called back via Split[0].

Split string with delimiter www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra string MainString = textBox1.Text; string[] Split = MainString.Split(new Char[] { ' ', ',', '.' }); for(int i =0; i<Split.Length; i++) MessageBox.Show(Convert.ToString(Split[i]));

The trim function has three variations: www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra The trim function has three variations: Trim: It strips all white spaces from both the start and end of the string. TrimStart: It strips all white spaces from the start of the string. TrimEnd: It strips all white spaces from the end of the string.

Trim Function string Name = textBox1.Text; www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra string Name = textBox1.Text; string NewName = Name.Trim(); MessageBox.Show("("+NewName+")"); string Name = textBox1.Text; string NewName = Name.TrimStart(); MessageBox.Show("(" + NewName + ")"); string Name = textBox1.Text; string NewName = Name.TrimEnd(); MessageBox.Show("(" + NewName + ")");

Strip “Remove” string www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra How you can strip a number of characters from a specified starting point within the string. The first number is the starting point in the string and the second is the amount of chars to strip.

Strip “Remove” string string MainString = textBox1.Text; www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra string MainString = textBox1.Text; int begin = Convert.ToInt16(textBox2.Text); int count = Convert.ToInt16(textBox3.Text); string NewString = MainString.Remove(begin, count); MessageBox.Show(NewSring);

Tour with C# String Variables www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra

Practice www.cst.ps/staff/mfarra www.facebook.com/mahmoudRfarra

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