The major features added in C# in each release

C# 2.0:

• Generics (.NET Framework support was added, and C# benefited from this)
• Partial Types
• Iterator pattern (the yield keyword)
• Anonymous methods (the delegate keyword)
• Nullable types
• Coalescing operator (??)
• Getter/setter separate accessiblity
• Method group conversions(delegates)
• Co- and Contra-variance for delegates
• Static classes

C# 3.0

• Object initializers
• Collection initializers
• Implicitly typed local variables (var keyword)
• Anonymous types
• Extension methods
• Query expressions
• Lambda expressions (=>)
• Expression trees
• Partial methods

C# 4.0

• Optional Parameters and Named Arguments
• Dynamic binding(dynamic type)
• Improved COM-Interop
• Generic co- and contravariance

C# 5.0

• Asynchronous methods
• Caller info attributes
• Compiler-as-a-service

C# 6.0

• Import of static type members into namespace
• Exception filters
• Await in catch/finally blocks
• Auto property initializers
• Default values for getter-only properties
• Expression-bodied members
• Null propagator (Succinct null checking)
• String Interpolation
• nameof operator
• Parameterless struct constructors
• Dictionary initializer

C# 7.0 (Proposals)

• Declaration expressions
• Parameter arrays for IEnumerable interfaces