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Accepted
Ramil
Asked:2025-03-02 18:38:21 +0000 UTC2025-03-02 18:38:21 +0000 UTC

使用另一个 Equals 覆盖 Equals

  • 772
public class User
{
    public string Name {get; set; }

    public override bool Equals(object obj)
        {
            if(obj == null) return false;

            if(GetType() != obj.GetType()) return false;

            User p = (User)obj;

            return Name.Equals(p.Name); // 1

            return Name == p.Name;  // 2
        }
}

重写 Equals 方法的正确方法是什么？

选项 1 - 在 Name 中的字符串上调用 Equals

选项 2 - 通过 == 进行比较

或者这些是等效方法？

c#

1 个回答

  1. Best Answer

    在我看来，最好在这里使用字符串来比较字符串string.Equals，此外，您还可以在那里设置一个参数：区分大小写、不区分大小写等。

    我会写类似这样的东西。

    public class User : IEquatable<User>
{
    public string Name { get; set; }

    public bool Equals(User other)
    {
        return other is not null && string.Equals(Name, other.Name, StringComparison.Ordinal);
    }

    public override bool Equals(object obj)
    {
        return Equals(obj as User);
    }

    public override int GetHashCode()
    {
        return Name?.GetHashCode() ?? 0;
    }
}

    如果我的观点还不够，这里有一个来自.NET 深处的例子，类HttpMethod：

    public partial class HttpMethod : IEquatable<HttpMethod>
{
    private readonly string _method;

    // ...

    private int _hashcode;

    // ...

    public bool Equals([NotNullWhen(true)] HttpMethod? other)
    {
        if (other is null)
        {
            return false;
        }

        if (object.ReferenceEquals(_method, other._method))
        {
            // Strings are static, so there is a good chance that two equal methods use the same reference
            // (unless they differ in case).
            return true;
        }

        return string.Equals(_method, other._method, StringComparison.OrdinalIgnoreCase);
    }

    public override bool Equals([NotNullWhen(true)] object? obj)
    {
        return Equals(obj as HttpMethod);
    }

    public override int GetHashCode()
    {
        if (_hashcode == 0)
        {
            _hashcode = StringComparer.OrdinalIgnoreCase.GetHashCode(_method);
        }

        return _hashcode;
    }

    // ...
}
    • 3

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