Lesson 13: More beautiful C#

Agenda

• Tuples
• Deconstruction
• Discard operator
• Expression trees
• GC
• Unsafe code
• Preprocessor
• Calling private method from outside a class
• Creating objects without knowing their type

Tuples

Tuple

• Tuples are data structures to carry a known set of items
• They can be useful when returning multiple values
• They are generic and can have many values (not just 2)
• Reference type

ValueTuple

• Value type tuple
• Works exactly like Tuple
• Is a default target for storing multiple values

https://stackoverflow.com/questions/41084411/whats-the-difference-between-system-valuetuple-and-system-tuple

Deconstructing tuples

• You don’t have to create a tuple in order to return multiple values with it
• Under the hood ValueTuple is returned in DemoTwoValuesReturn

Deconstructing other types

• void Deconstruct method
• out every parameter you want to deconstruct

Discard operator “_”

• Sometimes we don’t want to out all the data
• Maybe we don’t need any of it
• For example in TryParse we might only want if the parse was success

Expression trees

Expression trees

• Is a way to translate code into data (expressions)
• For every code element there is a kind of expression

https://docs.microsoft.com/en-us/archive/blogs/charlie/expression-tree-basics

Why do we need to translate code to data?

• Because we want to do the opposite- to translate data back in code
• If we want to execute code in multiple languages, maybe our domain-specific language- that’s the way to do it!

Practical examples: dynamic LINQ

• Another application- making combos of LINQ expressions

Practical examples: LINQ to SQL

• Is a way to translate code into data (expressions)
• For every code element there is a kind of expression

https://docs.microsoft.com/en-us/archive/blogs/charlie/expression-tree-basics

GC

Memory allocation

GC

• GC is Garbage Collector
• It exists in managed languages like C# or Java
• This means that we don’t care about freeing up memory of objects that we no longer use
• It also defragments the memory gaps

When does GC get activated

• The system has low physical memory
• The memory that's used by allocated objects on the managed heap surpasses an acceptable threshold. This threshold is continuously adjusted as the process runs
• The GC.Collect method is called

3 simple rules

• Avoid calling GC manually
• Understand, that GC frees memory allocated on the heap
• Object is ready to be GC’ed only when it is no longer referenced by anything (out of scope, not referenced by other object)

Unsafe code

Unsafe code

• There is a way to call code outside of CLR (common language runtime)
• This means we can call unmanaged code in C#
• It’s disabled by default
• In order to enable it, inside: .csproj add this line

Pandora box of unsafe code

• There are no guards and many risks for permanently corrupting memory
• Enables two features:
• Pointers
• Fixed buffer
• All unsafe code requires either unsafe type or unsafe code block

Pointer

• Pointer is similar to a reference type
• However, the fundamental difference is that a pointer points to a point in memory
• Reference points to an object
• Pointer is static

Pointer example

Fixed

• Fixed is used for a fixed size array
• Such array is declared with a size
• Cannot be initialized

Fixed: benefits

• Stays on the stack
• Does not get called by GC

Fixed: problems

• Does not get defragmented until application is closed
• Should not be abused

Preprocessor directives

Preprocessor

• Used for conditional compiling

#if..#endif

• Will compile only in a certain environment
• Environments can be:
• Debugging
• Some version of .NET
• Debug symbol

#pragma

• Can turn off warnings

Doing the impossible with reflection!

Calling private method from outside a class

Activator

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Compiled Lambda

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