learning_c#.md

path	title
/learnings/csharp	Learnings: Csharp

Table Of Contents

• variable declarations
  • "pointers" in method declarations
• classes
  • virtual methods
• casts
• Strings
• properties
• initializing objects
• checked variables
• control flow
  • foreach
• method syntax
• Null Handling
  • null coalscing operator
  • null conditional
• TODO:

variable declarations

string thing

"pointers" in method declarations

Parameters in C# are pass by "value": even if the copied value is a copy of an address pointer.

Thus, if you want to assign something to an incoming parameter, you need the ref keyword

void MyMethod( ref string outString ) {
    outString = "hi"
}

string userName = "temp"
MyMethod(ref userName)

Problem: userName variable needs to be initialized (compiler doesn't know you're just writing to it).

void MyMethod( out string outString ) {
   out = "hi"
}

string userName
MyMethod( userName )

NOTE:: method using out parameters must assign all out parameters!!!

classes

Features:

• single inheritence

public class Employee : Person {

}

virtual methods

Defaults to nonvirtual (???)

For virtual behavior need both virtual on base class and override on subclass.

casts

C style casts

Strings

@"this is a literal string \ this will show up like a backslash not escape character"


$"indicates that {variables} will be interpreted"

properties

In other words, a property has the behavior of special methods called setters and getters, but the syntax for accessing that behavior is that of a field.

initializing objects

Can initilize fields at object construction time, with handy syntax:

(C# 3.0)

Employee n = new Employee("Ryan", "Wilcox") {
    jobTitle = "Software Engineer",
    salary = "$"
}

checked variables

Will throw an exception if you try to overflow the variable type

This can be controlled by compiler OR by checked {} and unchecked {} variable block scopes

control flow

foreach

method syntax

public void name(TYPE varName)

Null Handling

null coalscing operator

"if this value is blank use that one": a ?? b

null conditional

C# 6.0

varThatCouldBeNull?.something

#preprocessors

Yes, C# has them.

Operations:

• #if
• #define
• #error
• #warning
• #pragma
• #line <-- override what line number is reported by the compiler in case or error or warning (!!!!!!)

TODO:

Q: Is the following how C# does annotations??

[TestMethod]
public void message() {
    1 + 1
}