C# - Expressions vs. Statements

csharp-expressions-statements.md

Statements

From Microsoft:
The actions that a program takes are expressed in statements.

• Do not return a value
• Cannot be chained
• May contain expressions
• Generally cannot be used as expressions

Expressions

From Microsoft:
"An expression is either a non_assignment_expression or an assignment."

"An expression is a sequence of one or more operands and zero or more operators that can be evaluated to a single value, object, method, or namespace"

• Resolves to a value
• Constructed from operators and operands
• Can be chained / combined to form other expressions
• Can be used as a statement

Statements

// Declaration statements
string message;
double cashInBank;
System.Text.StringBuilder sb;

// Assignment statements
message = "QWERTYUIOP";
cashInBank = 42.42;

// A declaration statement with an initializer can be viewed as
// a declaration statement followed by an assignment statement
int age = 42;
List<string> names = { "Samuel", "Bryce", "Conrad" };

// Selection statements contain (if, switch)
// Iteration statements contain (while, do, for, foreach)
// Jump statements contain (break, continue, goto, throw, return, yield)
// Other statements contain ( [try...catch], [try...finally], checked, unchecked, lock, using)

// Statement lambda
(input-params) => { <sequence-of-statements> };

Expressions

// by no means is this an exhaustive list

age = 44;                    // assignment expressions              
--age;                       // Decrement expression
new Foo();                   // Object instantiation expression
Foo.DoSomethingUseful(bar);  // Method call expression
y = MyHelpers.Add(1,1);      // Assignment expression

// Expression lambda
(input-params) => expression;