Conditions, switch and ternary

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Examples are independent C# snippets for modern .NET console projects unless noted otherwise. Class declarations and top-level code can live in Program.cs when top-level statements come first.

At a glance

Control flow chooses which statements execute. Use the simplest structure that communicates the rules correctly.

How it works

If, else if and else

if checks a boolean expression. An else if adds another test only when earlier conditions are false. A final else handles remaining cases. Order matters when conditions overlap.

int score = 82;
if (score >= 90)
    Console.WriteLine("Excellent");
else if (score >= 60)
    Console.WriteLine("Passed");
else
    Console.WriteLine("Try again");

Switch statements

switch is useful when one value determines several distinct cases. Cases can use pattern matching and guards, but a conventional switch is fine for straightforward menu commands.

string command = "start";
switch (command)
{
    case "start": Console.WriteLine("Running"); break;
    case "stop": Console.WriteLine("Stopped"); break;
    default: Console.WriteLine("Unknown command"); break;
}

Ternary and switch expressions

The conditional operator condition ? yes : no returns one of two expressions. Use it for small assignments, not complex nested business rules. A switch expression can produce a value from several cases.

int health = 0;
string state = health > 0 ? "Alive" : "Defeated";
string icon = state switch
{
    "Alive" => "+",
    _ => "x"
};
Console.WriteLine($"{state} {icon}");

Deep dive: a branch is a design decision

Evaluate conditions in order

An if/else if/else chain tests branches from top to bottom. The first true branch runs; later branches are skipped. Therefore order matters when rules overlap. For example, test score >= 90 before score >= 60 if the first branch represents a higher grade. Include a final else when you must handle values outside the intended ranges.

Use `switch` when one value selects an action

A switch statement expresses distinct cases for a selected value. A switch expression produces a value and is often clearer than assigning the same variable across many branches. When every possible enum member is important, handle cases explicitly and decide how unknown values should behave rather than silently swallowing them.

int score = 85;
string rank = score switch
{
    >= 90 => "Gold",
    >= 60 => "Silver",
    >= 0  => "Bronze",
    _     => "Invalid score"
};
Console.WriteLine(rank); // Silver

This example uses relational patterns. Branches are matched in order, so reversing the first two cases would incorrectly label a score of 95 as Silver.

Ternary operator versus an ordinary `if`

condition ? whenTrue : whenFalse produces one of two expressions, making it good for a small assignment. Nested ternary expressions quickly become hard to read; use a regular if or a switch expression for more complex rules. A conditional should show business intent rather than maximize the number of statements on one line.

Handle invalid states intentionally

Consider boundaries such as zero, a negative number, an empty input or an unknown enum value. When inputs come from players, files or network messages, validate them before making game-critical changes. A final _ pattern, guard clause, or thrown exception can document what should happen if no expected case matches.

When and why

Use if for ranges, switch for known alternatives and ternary for simple two-way expressions.

Common mistake

Check the order of overlapping conditions and avoid deeply nested ternary expressions.

Try it yourself

Write a rule that prints Low below 20, Medium below 80 and High otherwise.

Reveal a solution

if (value < 20) ... else if (value < 80) ... else ....