title: C# date: 2021-12-14 12:22:00 background: bg-[#8c4c8a] tags: - object-oriented - class categories: - Programming intro: |
class Hello {
// main method
static void Main(string[] args)
{
// Output: Hello, world!
Console.WriteLine("Hello, world!");
}
}
Compiling and running (make sure you are in the project directory) ```shell script $ dotnet run Hello, world!
### Variables
```cs
int intNum = 9;
long longNum = 9999999;
float floatNum = 9.99F;
double doubleNum = 99.999;
decimal decimalNum = 99.9999M;
char letter = 'D';
bool @bool = true;
string site = "quickref.me";
var num = 999;
var str = "999";
var bo = false;
Data Type | Size | Range |
---|---|---|
int |
4 bytes | -2^31^ ^to^ 2^31^-1 |
long |
8 bytes | -2^63^ ^to^ 2^63^-1 |
float |
4 bytes | 6 ^to^ 7 decimal digits |
double |
8 bytes | 15 decimal digits |
decimal |
16 bytes | 28 ^to^ 29 decimal digits |
char |
2 bytes | 0 ^to^ 65535 |
bool |
1 bit | true / false |
string |
2 bytes per char | N/A |
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// Single-line comment
/* Multi-line
comment */
// TODO: Adds comment to a task list in Visual Studio
/// Single-line comment used for documentation
/** Multi-line comment
used for documentation **/
string first = "John";
string last = "Doe";
// string concatenation
string name = first + " " + last;
Console.WriteLine(name); // => John Doe
See: Strings
Console.WriteLine("Enter number:");
if(int.TryParse(Console.ReadLine(),out int input))
{
// Input validated
Console.WriteLine($"You entered {input}");
}
int j = 10;
if (j == 10) {
Console.WriteLine("I get printed");
} else if (j > 10) {
Console.WriteLine("I don't");
} else {
Console.WriteLine("I also don't");
}
char[] chars = new char[10];
chars[0] = 'a';
chars[1] = 'b';
string[] letters = {"A", "B", "C"};
int[] mylist = {100, 200};
bool[] answers = {true, false};
int[] numbers = {1, 2, 3, 4, 5};
for(int i = 0; i < numbers.Length; i++) {
Console.WriteLine(numbers[i]);
}
foreach(int num in numbers) {
Console.WriteLine(num);
}
string first = "John";
string last = "Doe";
string name = first + " " + last;
Console.WriteLine(name); // => John Doe
string first = "John";
string last = "Doe";
string name = $"{first} {last}";
Console.WriteLine(name); // => John Doe
Member | Description |
---|---|
Length | A property that returns the length of the string. |
Compare() | A static method that compares two strings. |
Contains() | Determines if the string contains a specific substring. |
Equals() | Determines if the two strings have the same character data. |
Format() | Formats a string via the {0} notation and by using other primitives. |
Trim() | Removes all instances of specific characters from trailing and leading characters. Defaults to removing leading and trailing spaces. |
Split() | Removes the provided character and creates an array out of the remaining characters on either side. |
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```cs {.wrap} string longString = @"I can type any characters in here !#@$%^&*()__+ '' \n \t except double quotes and I will be taken literally. I even work with multiple lines.";
### Member Example
```cs
// Using property of System.String
string lengthOfString = "How long?";
lengthOfString.Length // => 9
// Using methods of System.String
lengthOfString.Contains("How"); // => true
Term | Definition |
---|---|
Runtime | A collection of services that are required to execute a given compiled unit of code. |
Common Language Runtime (CLR) | Primarily locates, loads, and managed .NET objects. The CLR also handles memory management, application hosting, coordination of threads, performaing security checks, and other low-level details. |
Managed code | Code that compiles and runs on .NET runtime. C#/F#/VB are examples. |
Unmanaged code | Code that compiles straight to machine code and cannot be directly hosted by the .NET runtime. Contains no free memory management, garbage collection, etc. DLLs created from C/C++ are examples. |
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