C# Type Casting

Implicit Conversion

Widening conversions never lose data, so C# applies them automatically.

int i = 42;
long l = i;     // implicit: int to long
double d = i;   // implicit: int to double

Explicit Cast

Narrowing can lose data, so it requires a cast operator. Fractional parts are truncated.

double d = 3.9;
int i = (int)d;   // 3 — truncates, no rounding

Parse Methods

Parse converts a string; TryParse returns success instead of throwing.

int n = int.Parse("42");
double x = double.Parse("3.14");

if (int.TryParse("maybe", out int result))
{
    Console.WriteLine(result);
}
else
{
    Console.WriteLine("not a number");
}

Convert Class

Convert converts between many types and takes care of culture and rounding details.

int n = Convert.ToInt32("42");
string s = Convert.ToString(123);
bool b = Convert.ToBoolean("true");

Safe Casting

as Operator

as returns null on failure instead of throwing. It works with reference types (and nullable value types).

object o = "hello";
string s = o as string;   // "hello"; null if not a string
if (s != null)
{
    Console.WriteLine(s);
}

is Operator

is tests a type and binds a typed variable in one step.

object o = 42;
if (o is int number)
{
    Console.WriteLine(number + 1); // 43
}

Pattern Casting

Combine a type test with a condition in a single pattern.

object o = "hello world";
if (o is string text && text.Length > 0)
{
    Console.WriteLine(text.ToUpper()); // HELLO WORLD
}