子類繼承基類,生成實例時,會先跑基類的構造函數,再跑子類的構造函數
class Program
{
public static void Main(string[] args)
{
ClassA clsA = new ClassA();
Console.ReadKey();
}
}
public class Base
{
public Base()
{
Console.WriteLine("Base");
}
}
public class ClassA : Base
{
public ClassA()
{
Console.WriteLine("ClassA");
}
}
結果如下:
然而在C#的類裏,一個類的構造函數並不是只限一個。當基類有多個構造函數的時候可以使用base關鍵詞給子類的構造函數選擇一個基類的構造函數。當子類構造函數不寫base的時候,默認爲base(),直接繼承基類的無參構造函數。
class Program
{
public static void Main(string[] args)
{
ClassA clsA = new ClassA();
Console.WriteLine();
ClassA clsA1 = new ClassA(1);
Console.WriteLine();
ClassA clsA2 = new ClassA(1,2);
Console.WriteLine();
ClassA clsA3 = new ClassA(1,"1");
Console.WriteLine();
ClassA clsA4 = new ClassA(1L);
Console.WriteLine();
ClassA clsA5 = new ClassA(1f);
Console.ReadKey();
}
}
public class Base
{
public Base()
{
Console.WriteLine("Base");
}
public Base(int a)
{
Console.WriteLine("Base int a");
}
public Base(string a)
{
Console.WriteLine("Base string a");
}
}
public class ClassA : Base
{
public ClassA()
{
Console.WriteLine("ClassA");
}
public ClassA(int a):base(a)
{
Console.WriteLine("ClassA int a");
}
public ClassA(int a, int b) : base(a)
{
Console.WriteLine("ClassA int a int b");
}
public ClassA(int a, string b) : base(b)
{
Console.WriteLine("ClassA int a string b");
}
public ClassA(long a) : base()
{
Console.WriteLine("ClassA long a");
}
public ClassA(float a)
{
Console.WriteLine("ClassA float a");
}
}
結果如下: