1. Initialize the array:

string[] s1 = { " aaa " , " bbb " , " ccc " }   // Direct assignment
string[] s2 = new string[5] { " aaa " , " bbb " , " ccc " }; // Assignment plus specified length
string[] s3 =  new string[]{ " aaa " , " bbb " , " ccc " };
string[] s4 = new string[5];  // Direct assignment with a loop

2. Traversal groups:

foreach (string s in str)
{
　　Console.Write(s);
}

3. 2-d array:

string [and] arr2; // declares a 2-dimensional array string [and] arr3; // declares a multidimensional array 4. Jagged array: An array with different lines for each 1.

5. The interface

You can use the new modifier to hide the interface inherited from the base class

public class Class2:Class1
{
　　new public interface Iinterface
　　{
　　void Print();
　　}
}

Inherit multiple interfaces:

public interface Iinterface3 : Iinterface1, Iinterface2, Iinterface3
{
　　void Print3();
}

Interface properties, methods, etc., can not be implemented, can only be declared. Such as:

public interface Iinterface
{
　　string Name
　　{
　　get;
　　set;
　　}
}

Implementation interface: public class Program : Iinterface Abstract classes and interfaces: Abstract class features: cannot be sealed, cannot be instantiated directly, and can contain abstract members

Differences between abstract classes and interfaces: A class can implement multiple interfaces, but can only have one parent class; Interfaces cannot contain non-abstract methods, but they can exist in abstract classes. Abstract class is an incomplete class, and interface is a behavior specification. Interfaces don’t have any of the basic features of inheritance, they just promise methods that can be called.