10 个 C# 关键字和功能

C#
1
public async Task<string> GetDataAsync()
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{
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    using (HttpClient client = new HttpClient())
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    {
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        string result = await client.GetStringAsync("http://bing.com");
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        return result;
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    }
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}

C#
1
var query = from student in students
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            where student.Age > 18
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            orderby student.Name
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            select student;

C#
1
class Person
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{
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  private string name; // backing field
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  public string Name   // property
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  {
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    get { return name; }
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    set { name = value; }
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  }
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}
10
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class Program
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{
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  static void Main(string[] args)
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{
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    Person P1 = new Person();
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    P1.Name = "Sunny";
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    Console.WriteLine(myObj.Name);
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  }
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}

C#
1
public class Print
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{
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    // Generic method which can take any datatype as method parameter
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    public void Display<T>(T value)
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    {
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        Console.WriteLine($"The value is: {value}");
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    }
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}
9
10
public class Program
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{
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    public static void Main(string[] args)
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{
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        Print print = new Print();
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        // Call the generic method with different data types
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        print.Display<int>(10);
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        print.Display<string>("Hello World");
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        print.Display<double>(20.5);
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    }
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}

C#
1
public delegate void MyDelegate1(string msg); // declare a delegate
2
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// This method will be pointed to by the delegate
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public static void PrintMessage(string message)
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{
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    Console.WriteLine(message);
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}
8
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public static void Main(string[] args)
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{
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    // Instantiate the delegate
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    MyDelegate1 del = PrintMessage;
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    // Call the method through the delegate
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    del("Hello World");
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}

C#
1
// Declare a delegate
2
public delegate void Notify();  
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4
public class ProcessBusinessLogic
5
{
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    public event Notify ProcessCompleted; // Declare an event
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8
    public void StartProcess()
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{
10
        Console.WriteLine("Process Started!");
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        // Some actual work here..
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        OnProcessCompleted();
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    }
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    // Method to call when the process is completed
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    protected virtual void OnProcessCompleted()
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{
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        ProcessCompleted?.Invoke();
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    }
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}
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public class Program
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{
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    public static void Main(string[] args)
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{
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        ProcessBusinessLogic bl = new ProcessBusinessLogic();
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        bl.ProcessCompleted += bl_ProcessCompleted; // Register event handler
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        bl.StartProcess();
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    }
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    // Event handler
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    public static void bl_ProcessCompleted()
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{
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        Console.WriteLine("Process Completed!");
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    }
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}

C#
1
Func<int, int, int> add = (x, y) => x + y;
2
3
int result = add(3, 4);  // result is 7

C#
1
int? num = null;
2
if (num.HasValue)
3
{
4
    Console.WriteLine($"Number: {num.Value}");
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}
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else
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{
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    Console.WriteLine("No value assigned.");
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}

C#
1
object obj = 5;
2
3
if (obj is int i)
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{
5
    Console.WriteLine($"Integer: {i}");
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}
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switch (obj)
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{
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    case int j:
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        Console.WriteLine($"Integer: {j}");
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        break;
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    case string s:
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        Console.WriteLine($"String: {s}");
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        break;
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    default:
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        Console.WriteLine("Unknown type.");
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        break;
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}

C#
1
public static class StringExtensions
2
{
3
    public static bool IsNullOrEmpty(this string value)
4
{
5
        return string.IsNullOrEmpty(value);
6
    }
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}
8
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// Usage
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string str = null;
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bool result = str.IsNullOrEmpty();  // result is true

C#
1
public (int, string) GetPerson()
2
{
3
    return (1, "John Doe");
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}
5
6
// Usage
7
var person = GetPerson();
8
Console.WriteLine($"ID: {person.Item1}, Name: {person.Item2}");