C# Version HisotryC# Language FeaturesInstalling Visual StudioC# Basic Project StructureHello Wolrd, first C# program
Variables in C# Explicitly typed variables in C#Implicitly typed variables in C#Constants in C#Data types in C#Integral data types in C#Floating-point data types in C#Comparison between Float, Double and DecimalChar data type in C#String data type in C#Boolean data type in C#DateTime data type in C#Enumeration data type in C#Array data type in C#Object data type in C#Dynamic data type in C#Anonymous data type in C#Nullable data type in C#Type casting in C#Type safety in C#Literals in C#Operators in C#Ternary Operator in C#Null coalescing Operator in C#Tilde(~) Operator in C#Keywords in C#Namespace in C#Nullable Types in C#Nullable Helper Class in C#Characteristics of Nullable typesC# Difference between "int" and "int?"
Block statement in C#Empty statement in C#Jump statements in C#Break statement in C#Continue statement in C#Difference between continue and breakGoto statement in C#Return statement in C#Throw statement in C#Yield keyword in C#Checked statement in C#Unchecked statement in C#Lock statement in C#Using statement in C#Enum/Enumeration in C#If-Else statement in C#Switch statement in C#What is a loop in C#?For loop in C#While loop in C#Do while loop in C#Foreach loop in C#Nested loop in C#Infinite loop in C#
C# Method or FunctionC# Method Parameters and ArgumentsC# Method OverloadingC# Return StatementsC# Static vs. Instance MethodsC# Method ModifiersC# Method Signatures and Naming ConventionsC# Function Documentation and CommentsC# Value Type ParametersC# Ref Type ParametersDifference between Value and Ref TypeC# Out ParametersDifference between Ref and out parametersC# Optional parametersAre Nullable types reference types in C#"
Exception Handling in C#Types of exception in C#Try catch finally in C#finally block in C#try block without catch blockMultiple catch blocks in exceptionCatch multiple exceptions in C#Base class of exception in C#finally block execution in C#finally block execution in case of errorFinally and return statementWays to use try-catch-finallyException throw from finally block"throw" and "throw ex" in C#Differene between finalize() and finallyInner exception in C#Error types in C#Catch multi exception by single catch blockUser defined/custom excetion in C#Compile and run time exception in C#Difference between "error" and "exception"System and application exception in C#Exception handling abuse in c#?
C# String BasicsC# String ManipulationC# String FormattingC# String Comparison and SearchingC# StringBuilder ClassC# Regular ExpressionsC# Unicode and EncodingC# String Parsing and ConversionDifference between "string" and "String"C# String Escape SequenceC# Mutable and Immutable ConceptProve that string is immutableString value stored in memoryDifference between string and stringbuilderOverride the tostring() method
Enum/enumeration in C#Can you inherit enum in C#?Convert enum to stringConvert enum to list in C#Cast int value to enum in C#Get int value from enum in C#Convert string to enum in C#Usage of enum in switch case statementLoop through all enum valuesUse tilde(~) with Enum
Main() method basics in C#More than one "Main()" method in C#Static Main() method in C#Overload Main() method in C#Override Main() method in C#Access modifiers of Main() method in C#Non-static method in C#Main() method arguments and return typeasync Main() method in C#Class without Main() method in C#Main() method rules in C#
Recursion in C#Base condition in recursion in C#Recursive Algorithms in C#Tree traversal using recursion in C#Stack overflow error in recursionBack tracking using recursionIndirect recursion in C#Recursive data structures in C#Tail Recursion in C#Recursive problem solvingRecursion vs Iteration
C# File and File InfoC# StreamReader and StreamWriterC# FileStream and BinaryReader/BinaryWriterC# Directory and DirectoryInfo ClassesC# File PathsC# File and Directory OperationsC# File Exceptions and Error HandlingC# File Serialization and DeserializationC# File System Watcher
What is array?Single dimension arrayMulti dimension arrayJagged arrayParam arrayArray with multi data typesDifferent data types from object arrayArray with non-default valuesArray methods and propertiesArray manipulation techniquesArray sorting algorithmsArray Searching algorithms(linear, binary search)Array finding maximum and minimumArray of Reference Types
C# GenericsC# Generic Constraints
C# ArrayListC# Array vs ArrayListC# ListC# SortedListC# DictionaryC# HashtableC# Dictionary vs HashtableC# HashSetC# Hashtable vs HashSetC# StackC# Queue
C# IEnumerableC# IEnumeratorC# ICollectionC# IListC# IDictionaryC# IDisposableC# IComparableC# IEquatableC# ICloneableC# IQueryableC# INotifyPropertyChangedC# INotifyCollectionChangedC# IFormattableC# IAsyncResultC# IComparerC# IEqualityComparerC# IHttpHandlerC# IHttpModule
C# DelegatesC# Single-Cast DelegateC# Multi-Cast DelegateC# Generic DelegatesC# Func DelegateC# Action DelegateC# Predicate DelegateC# Anonymous MethodsC# EventsDifference Between Event & DelegateDifference Between Interface & DelegateC# Covariance and Contravariance
Previous
Next

C# - String Comparison and Searching: A Comprehensive Guide

In C#, string comparison and searching are essential operations for working with text data. Whether you’re checking if two strings are equal, finding the position of a substring, or determining if a string starts or ends with a specific pattern, C# provides a variety of methods to accomplish these tasks. In this guide, we’ll explore the key methods for string comparison and searching, along with practical examples to help you master these operations.

1. String Comparison

String comparison involves determining if two strings are equal, or if one string comes before or after another in lexicographic (dictionary) order. C# provides several methods for comparing strings, including string.Equals and string.Compare.

a. string.Equals

The Equals method compares two strings for equality and returns a Boolean value (true or false). You can also specify whether the comparison should be case-sensitive or case-insensitive.

Example:

string str1 = "Hello";
string str2 = "hello";

// Case-insensitive comparison
bool areEqual = str1.Equals(str2, StringComparison.OrdinalIgnoreCase);
Console.WriteLine(areEqual); // Output: True

Key Points:

  • Use StringComparison.OrdinalIgnoreCase for case-insensitive comparisons.
  • Use StringComparison.Ordinal for case-sensitive comparisons.

b. string.Compare

The Compare method compares two strings and returns an integer that indicates their relative position in lexicographic order:

  • A negative value means the first string comes before the second.
  • A positive value means the first string comes after the second.
  • Zero means the strings are equal.

Example:

string str1 = "apple";
string str2 = "banana";

// Case-insensitive comparison
int result = string.Compare(str1, str2, StringComparison.OrdinalIgnoreCase);

if (result < 0)
Console.WriteLine("str1 comes before str2.");
else if (result > 0)
Console.WriteLine("str1 comes after str2.");
else
Console.WriteLine("str1 and str2 are equal.");

Key Points:

  • Use StringComparison.OrdinalIgnoreCase for case-insensitive comparisons.
  • Use StringComparison.Ordinal for case-sensitive comparisons.

2. String Searching

String searching involves locating substrings within a larger string. C# provides several methods for searching strings, including Contains, IndexOf, LastIndexOf, StartsWith, and EndsWith.

a. string.Contains

The Contains method checks if a substring exists within a string and returns a Boolean value (true or false).

Example:

string sentence = "The quick brown fox jumps over the lazy dog.";

bool containsFox = sentence.Contains("fox");
Console.WriteLine(containsFox); // Output: True

Key Points:

  • Contains is case-sensitive by default. Use ToLower or ToUpper for case-insensitive searches.

b. string.IndexOf

The IndexOf method returns the index of the first occurrence of a substring within a string. If the substring is not found, it returns -1.

Example:

string sentence = "The quick brown fox jumps over the lazy dog.";

int index = sentence.IndexOf("fox");
Console.WriteLine(index); // Output: 16

Key Points:

  • Use IndexOf to find the position of a substring.
  • Combine with Substring to extract parts of a string.

c. string.LastIndexOf

The LastIndexOf method is similar to IndexOf, but it searches for the last occurrence of a substring within a string.

Example:

string sentence = "The quick brown fox jumps over the lazy dog.";

int lastIndex = sentence.LastIndexOf("o");
Console.WriteLine(lastIndex); // Output: 40

Key Points:

  • Use LastIndexOf to find the position of the last occurrence of a substring.

d. string.StartsWith and string.EndsWith

These methods check if a string starts or ends with a specific substring and return a Boolean value.

Example:

string fileName = "example.txt";

bool startsWithEx = fileName.StartsWith("ex");
Console.WriteLine(startsWithEx); // Output: True

bool endsWithTxt = fileName.EndsWith(".txt");
Console.WriteLine(endsWithTxt); // Output: True

Key Points:

  • Use StartsWith and EndsWith for pattern matching at the beginning or end of a string.

e. string.Substring

The Substring method extracts a portion of a string based on a start index and optional length.

Example:

string sentence = "The quick brown fox jumps over the lazy dog.";

string subString = sentence.Substring(16, 3);
Console.WriteLine(subString); // Output: "fox"

Key Points:

  • Use Substring to extract specific parts of a string.
  • Be cautious with the start index and length to avoid ArgumentOutOfRangeException.

3. Best Practices for String Comparison and Searching

  • Use Case-Insensitive Comparisons When Needed: Use StringComparison.OrdinalIgnoreCase for case-insensitive comparisons.
  • Avoid Hardcoding Indexes: Use IndexOf or LastIndexOf to dynamically find positions of substrings instead of hardcoding indexes.
  • Handle Edge Cases: Always check if IndexOf or LastIndexOf returns -1 (substring not found) before using the result.
  • Use Contains for Simple Existence Checks: Use Contains when you only need to check if a substring exists, without needing its position.
  • Combine Methods for Advanced Searches: Combine IndexOf, Substring, and other methods for more complex string manipulations.
  • Use StartsWith and EndsWith for Pattern Matching: These methods are efficient for checking prefixes and suffixes.

Conclusion

String comparison and searching are fundamental operations in C# programming. By mastering methods like Equals, Compare, Contains, IndexOf, StartsWith, and EndsWith, you can efficiently work with text data in your applications. Whether you’re validating user input, parsing data, or performing advanced string manipulations, these methods provide the tools you need to get the job done.

Remember to choose the right method for your specific use case and follow best practices to write clean, efficient, and maintainable code. With these skills, you’ll be well-equipped to handle any string-related challenge in C#.

Previous
Next