如何在C#中初始化结构 [英] How to initialize a struct in C#
问题描述
我有一些代码可以在C#中初始化结构:
I have some code to initialize a struct in C#:
namespace Practice
{
public struct Point
{
public int _x;
public int _y;
public int X
{
get { return _x; }
set { _x = value; }
}
public int Y
{
get { return _y; }
set { _y = value; }
}
public Point(int x, int y)
{
_x = x;
_y = y;
}
}
class Practice
{
public static void Main()
{
Point p1;
p1.X = 1;
p1.Y = 2;
}
}
}
上面的代码给出了一个编译器错误:
The above code gives a compiler error:
错误CS0165:使用未分配的本地 变量"p1"
error CS0165: Use of unassigned local variable 'p1'
为什么会引发此错误?
推荐答案
在知道所有字段已被填充之前,您不能在结构中使用属性内.
You can't use a property in a struct until it knows all the fields have been filled in.
例如,在您的情况下,应编译:
For example, in your case this should compile:
Point p1;
p1._x = 1;
p1._y = 2;
int x = p1.X; // This is okay, now the fields have been assigned
请注意,您不必在这里必须显式调用构造函数……尽管在封装良好的结构中,您几乎总是必须.您可以免除此费用的唯一原因是因为您的字段是公共的.哎呀.
Note how you don't have to explicitly call a constructor here... although in well-encapsulated structs you almost always would have to. The only reason you can get away with this is because your fields are public. Ick.
但是,我强烈建议您不要无论如何都使用可变结构.如果您确实想要一个结构,请使其不可变,然后将值传递给构造函数:
However, I would strongly advise you not to use a mutable struct anyway. If you really want a struct, make it immutable and pass the values into the constructor:
public struct Point
{
private readonly int x;
public int X { get { return x; } }
private readonly int y;
public int Y { get { return y; } }
public Point(int x, int y)
{
this.x = x;
this.y = y;
}
}
...
Point p1 = new Point(1, 2);
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