C# 比较参考值和值

Question

将值传递给此方法时，我遇到了麻烦。

注意：使用此 function 的系统在我看来是一个黑盒子，因此无法更改。

问题是，将相同的值（如字符串、布尔值、对象等）传递给方法会说它们不相等，即使值相同。 我认为这是因为一个是参考，而另一个是值，因此它们“不同”。

    protected void SetData<T>(ref T field, T value)
        {
            if (!EqualityComparer<T>.Default.Equals(field, value))
            {
                Console.WriteLine("They are NOT equal");
            }
            else
            {
                Console.WriteLine("They are equal");
            }
        }

为了测试这个假设，我做了一些不同的单元测试。

        public bool AreEqual<T>(ref T field, T value)
        {
            return EqualityComparer<T>.Default.Equals(field, value);
        }

---

    [TestMethod]
    public void IsDirtyString()
    {
        var tc = new Program();
        var field = "Germany";
        var value = "United States";
        var result = tc.AreEqual(ref field, value);
        Assert.IsFalse(result);
    }
    [TestMethod]
    public void IsNotDirtyString()
    {
        var tc = new Program();
        var field = "Nepal";
        var value = "Nepal";
        var result = tc.AreEqual(ref field, value);
        Assert.IsTrue(result);
    }
    [TestMethod]
    public void IsDirtyDouble()
    {
        var tc = new Program();
        var field = 11.2;
        var value = 12.3;
        var result = tc.AreEqual(ref field, value);
        Assert.IsFalse(result);
    }
    [TestMethod]
    public void IsNotDirtyDouble()
    {
        var tc = new Program();
        var field = 12.3;
        var value = 12.3;
        var result = tc.AreEqual(ref field, value);
        Assert.IsTrue(result);
    }
    [TestMethod]
    public void IsDirtyInt()
    {
        var tc = new Program();
        var field = 12;
        var value = 15;
        var result = tc.AreEqual(ref field, value);
        Assert.IsFalse(result);
    }
    [TestMethod]
    public void IsNotDirtyInt()
    {
        var tc = new Program();
        var field = 12;
        var value = 12;
        var result = tc.AreEqual(ref field, value);
        Assert.IsTrue(result);
    }
    [TestMethod]
    public void IsDirtyBool()
    {
        var tc = new Program();
        var field = true;
        var value = false;
        var result = tc.AreEqual(ref field, value);
        Assert.IsFalse(result);
    }
    [TestMethod]
    public void IsNotDirtyBool()
    {
        var tc = new Program();
        var field = true;
        var value = true;
        var result = tc.AreEqual(ref field, value);
        Assert.IsTrue(result);
    }

结果是单元测试都通过了......“预期”

因此，当我测试时，它按预期工作，但是当我连接到系统的 rest 并进行调试时，我可以看到“字段”和“值”的值，但它没有。

有没有人尝试过这样的事情？

Answer 1

您缺少平等比较器。

正如您在此示例中看到的那样，即使等于，output 也会为假：

class Program
{
    static void Main(string[] args)
    {
        Pizza pizza1 = new Pizza(1);
        Pizza pizza2 = new Pizza(1);
        bool equal = AreEqual(pizza1, pizza2);
        Console.WriteLine(equal);
    }

    public static bool AreEqual<T>(T field, T value)
    {
        return EqualityComparer<T>.Default.Equals(field, value);
    }
}

public class Pizza
{
    public Pizza(int slices)
    {
        Slices = slices;
    }
    public int Slices { get; set; }
}

Output：

错误的

---

这样它甚至可以使用自定义对象：

class Program
{
    static void Main(string[] args)
    {
        Pizza pizza1 = new Pizza(1);
        Pizza pizza2 = new Pizza(1);
        bool equal = AreEqual(pizza1, pizza2, new PizzaComparer());
        Console.WriteLine(equal);
    }

    public static bool AreEqual<T>(T field, T value, IEqualityComparer<T> equalityComparer)
    {
        return equalityComparer.Equals(field, value);
    }
}

public class Pizza
{
    public Pizza(int slices)
    {
        Slices = slices;
    }
    public int Slices { get; set; }
}

public class PizzaComparer : IEqualityComparer<Pizza>
{
    public bool Equals(Pizza pizza1, Pizza pizza2)
    {
        return pizza1.Slices == pizza2.Slices;
    }

    public int GetHashCode(Pizza pizza)
    {
        return pizza.Slices.GetHashCode();
    }
}

Output：

真的