C# 比較參考值和值

Question

將值傳遞給此方法時，我遇到了麻煩。

注意：使用此 function 的系統在我看來是一個黑盒子，因此無法更改。

問題是，將相同的值（如字符串、布爾值、對象等）傳遞給方法會說它們不相等，即使值相同。 我認為這是因為一個是參考，而另一個是值，因此它們“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");
            }
        }

為了測試這個假設，我做了一些不同的單元測試。

        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);
    }

結果是單元測試都通過了......“預期”

因此，當我測試時，它按預期工作，但是當我連接到系統的 rest 並進行調試時，我可以看到“字段”和“值”的值，但它沒有。

有沒有人嘗試過這樣的事情？

Answer 1

您缺少平等比較器。

正如您在此示例中看到的那樣，即使等於，output 也會為假：

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：

錯誤的

---

這樣它甚至可以使用自定義對象：

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