在C#中更改结构的属性值

Question

我正在读一本书,发现结构实际上是不可变的对象.但他们有吸气剂和制定者.我想知道结构的属性是否可以在创建后更改.

public struct Test 
{
    public string str {get; set; }
    public int int1 {get; set; }
}

'str'和'int1'的值一旦被赋值,是否可以更改？

Answer 1

结构可以是可变的也可以是不可变的,但根据许多人的说法它们应该是不可变的.

你的例子是一个可变的结构.

使用示例:

var t = new Test();
// t.str is null, and t.int1 is 0

t.str = "changed!"; // OK

var t2 = t;
t2.int1 = 42;
// t.int1 is still 0

var li = new List<Test> { t, t2, };
t.int1 = 666;  // OK, but copy in li is unaffected

li[0].int1 = 911;  // compile-time error, not a variable

var t3 = t2;
bool checkA = (t3 == t2);  // compile-time error, you did not overload operator ==
bool checkB = t3.Equals(t2);  // OK, true, ValueType class overrides Equals for you
bool checkC = t2.Equals(t);  // OK, false
bool checkD = object.ReferenceEquals(t, t);  // false, two distinct boxes
                                             // same as (object)t==(object)t

根据请求,这是一种使struct不可变的方法:

public struct Test 
{
    public string str { get; private set; }
    public int int1 { get; private set; }

    public Test(string str, int int1) : this()
    {
        this.str = str;
        this.int1 = int1;
    }
}
// if you introduce methods (other than constructors) that use the private setters,
// the struct will no longer be immutable

这是另一个:

public struct Test 
{
    readonly string m_str;
    readonly int m_int1;

    public string str { get { return m_str; } }
    public int int1 { get { return m_int1; } }

    public Test(string str, int int1)
    {
        m_str = str;
        m_int1 = int1;
    }
}