这个初始化方法有什么区别？

Question

What is the difference between this two codes?

class SomeClass   
{   

   SomeType val = new SomeType();   

}   

and

class SomeClass  
{      
   SomeType val;   

   SomeClass()   
   {   
       val = new SomeType();   
   }   

}   

Which method is preferd?

Answer 1

There is almost not difference between them. The assignment of the field will happen within the constructor in both cases. There is a difference in how this happpens in relation to base class constructors though. Take the following code:

class Base
{
    public Base()
    {

    }
}

class One : Base
{
    string test = "text";
}

class Two : Base
{
    string test;
    public Two()
    {
        test = "text";
    }
}

In this case the base class constructor will be invoked after the field assignment in the class One , but before the assignment in class Two .

Answer 2

第一个版本允许您定义多个构造函数，而不必记住在每个构造函数中放置= new SomeType() 。