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Essential C# Extension Methods  Suggest an edit

Null checking

Extension methods are static methods which behave like instance methods. However, unlike what happens when calling an instance method on a null reference, when an extension method is called with a null reference, it does not throw a NullReferenceException. This can be quite useful in some scenarios.

For example, consider the following static class:

public static class StringExtensions
{
    public static string EmptyIfNull(this string text)
    {
        return text ?? String.Empty;
    }

    public static string NullIfEmpty(this string text)
    {
        return String.Empty == text ? null : text;
    }
}
string nullString = null;
string emptyString = nullString.EmptyIfNull();// will return ""
string anotherNullString = emptyString.NullIfEmpty(); // will return null

Live Demo on .NET Fiddle

Extension Methods/
Extension Methods
Extension methods - overview
Null checking
Explicitly using an extension method
Generic Extension Methods
Extension methods can only see public or internal members of the extended class
Extension methods for chaining
Extension methods with Enumeration
Extension methods dispatch based on static type
Extension methods on Interfaces
Extension methods arent supported by dynamic code
Extension methods in combination with interfaces
Extensions and interfaces together enable DRY code and mixin-like functionality
IListT Extension Method Example Comparing 2 Lists
Extension methods as strongly typed wrappers
Using Extension methods to create mapper classes
Using Extension methods to build new collection types e.g. DictList
Extension methods for handling special cases
Using Extension methods with Static methods and Callbacks
Table Of Contents
1 Getting Started With C#
2 Literals
3 Operators
4 Conditional Statements
5 Equality Operator
6 Equals and GetHashCode
7 Null-Coalescing Operator
8 Null-Conditional Operators
9 nameof Operator
10 Verbatim String
11 Common String Operations
12 String Format
13 String Concatenate
14 String Manipulation
15 String Interpolation
16 String Escape Sequences
17 StringBuilder
18 Regex
19 DateTime
20 Arrays
21 On Algorithm for circular rotation of an array
22 Enum
23 Tuples
24 Overview of C# collections
25 GUID
26 BigInteger
27 Collection Initializers
28 Looping
29 Iterators
30 IEnumerable
31 Value type vs Reference type
32 Built-in Types
33 Aliases of built-in types
34 Anonymous types
35 Dynamic type
36 Type Conversion
37 Casting
38 Nullable types
39 Constructors and Finalizers
40 Access Modifiers
41 Interfaces
42 Static Classes
43 Singleton Implementation
44 Dependency Injection
45 Partial class and methods
46 Object Initializers
47 Methods
48 Extension Methods
49 Named Arguments
50 Named And Optional Arguments
51 Data Annotation
52 Keywords
53 Recursion
54 Naming Conventions
55 XML Documentation Comments
56 Comments and regions
57 Inheritance
58 Generics
59 Using Statement
60 Using Directive
61 IDisposable interface
62 Reflection
63 IQueryable interface
64 LINQ to Objects
65 LINQ Queries
66 LINQ to XML
67 Parallel LINQ PLINQ
68 XmlDocument
69 XDocument
70 C# 7.0 Features
71 C# 6.0 Features
72 C# 5.0 Features
73 C# 4.0 Features
74 C# 3.0 Features
75 Exception Handling
76 NullReferenceException
77 Handling FormatException
78 Read and Understand Stack trackes
79 Diagnostics
80 Overflow
81 JSON handling
82 Using json.net
83 Lambda Expressions
84 Lambda expressions
85 Generic Lambda Query Builder
86 Properties
87 Initializing Properties
88 INotifyPropertyChanged interface
89 Events
90 Expression Trees
91 Overload Resolution
92 Preprocessor directives
93 Structs
94 Attributes
95 Delegates
96 File and Stream IO
97 Networking
98 Performing HTTP requests
99 Reading and writing .zip files
100 FileSystemWatcher
101 Asynchronous Socket
102 Action Filters
103 Polymorphism
104 Immutability
105 Indexer
106 Checked and Unchecked
107 Stream
108 Timers
109 Stopwatches
110 Threading
111 Async/Await, BackgroundWorker, Task and Thread examples
112 Async Await
113 Synchronization Context in Async/Await
114 BackgroundWorker
115 Task Parallel Library
116 Making a variable thread safe
117 Lock Statement
118 Yield Keyword
119 Task Parallel Library TPL Dataflow Constructs
120 Functional Programming
121 Func delegates
122 Function with multiple return values
123 Binary Serialization
124 ICloneable
125 IComparable
126 Accessing Databases
127 Using SQLite
128 Caching
129 Code Contracts
130 Code Contracts and Assertions
131 Structural Design Patterns
132 Creational Design Patterns
133 Implementing Decorating Design Pattern
134 Implementing Flyweight Design Pattern
135 System.Management.Automation
136 Pointers
137 Pointers and Unsafe Code
138 Simulating C Unions with C# Structs
139 Reactive Extensions Rx
140 AsseblyInfo.cs examples
141 Creating Console Application
142 CLSCompliantAttribute
143 ObservableCollection<T>
144 Hash Functions
145 Generating Random Numbers
146 Cryptography
147 Unsafe Code in .NET
148 C# Script
149 Runtime Compile
150 Interoperability
151 .NET Compiler Platform Roslyn
152 Creating Own MessageBox in Windows Form Application
153 Including Font Resources
154 Garbage Collector
155 Windows Communication Foundation
156 Contributors
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