Question

我想知道如何比较两个对象（属于同一类），如string.Compare()方法。

有没有办法做到这一点？

Answer 1

您可以实施IComparable界面，例如sugested here：

public class Temperature : IComparable 
{
    // The temperature value 
    protected double temperatureF;

    public int CompareTo(object obj) {
        if (obj == null) return 1;

        Temperature otherTemperature = obj as Temperature;
        if (otherTemperature != null) 
            return this.temperatureF.CompareTo(otherTemperature.temperatureF);
        else 
           throw new ArgumentException("Object is not a Temperature");
    }
  ...

source

您将使用CompareTo方法比较您班级的项目。有关IComparable的更多信息，请访问SO。拥有CompareTo后，您可以根据比较函数对对象列表进行排序，如提到的here

Answer 2

您需要实现IComparable接口。

private class sortYearAscendingHelper : IComparer
{
   int IComparer.Compare(object a, object b)
   {
      car c1=(car)a;
      car c2=(car)b;
      if (c1.year > c2.year)
         return 1;
      if (c1.year < c2.year)
         return -1;
      else
         return 0;
   }
}

可以找到原始帖子 Here

Answer 3

由于对象是引用类型，因此您应该使用 obj.Equals（）方法。还要注意：

string.ReferenceEquals(str, str2);

它显然比较了参考文献。

str.Equals(str2)

首先尝试比较参考文献。然后它尝试按值进行比较。

str == str2

与Equals相同。

Answer 4

您可以检查两个相等的参考平等和价值平等

参考平等

引用相等意味着两个对象引用引用相同的底层对象。这可以通过简单的赋值来实现，如以下示例所示。

class Test
{
    public int Num { get; set; }
    public string Str { get; set; }

    static void Main()
    {
        Test a = new Test() { Num = 1, Str = "Hi" };
        Test b = new Test() { Num = 1, Str = "Hi" };

        bool areEqual = System.Object.ReferenceEquals(a, b);
        // Output will be false
        System.Console.WriteLine("ReferenceEquals(a, b) = {0}", areEqual);

        // Assign b to a.
        b = a;

        // Repeat calls with different results.
        areEqual = System.Object.ReferenceEquals(a, b);
        // Output will be true
        System.Console.WriteLine("ReferenceEquals(a, b) = {0}", areEqual);


    }
}

价值平等

值相等意味着两个对象包含相同的值。对于原始值类型（如int或bool），值相等的测试很简单。

Answer 5

比较两个对象请访问

http://comparenetobjects.codeplex.com/

Answer 6

public class BaseEntity
{
    public int Id { get; set; }
}

public class Product : BaseEntity
{
   public string Name { get; set; }
   public decimal Price { get; set; }
}

//Generic Comparer
public class EntityComparer<T> :  IEqualityComparer<T>, IComparer<T> 
where T : BaseEntity
{
    public enum AscDesc : short
    {
        Asc, Desc
    }

    #region Const
    public string PropertyName { get; set; }
    public AscDesc SortType { get; set; }
    #endregion

    #region Ctor
    public EntityComparer(string _propertyname = "Id", AscDesc _sorttype = AscDesc.Asc)
    {
        this.PropertyName = _propertyname;
        this.SortType = _sorttype;
    }
    #endregion

    #region IComparer
    public int Compare(T x, T y)
    {
        if (typeof(T).GetProperty(PropertyName) == null)
            throw new ArgumentNullException(string.Format("{0} does not contain a property with the name \"{1}\"", typeof(T).Name, PropertyName));

        var xValue = (IComparable)x.GetType().GetProperty(this.PropertyName).GetValue(x, null);
        var yValue = (IComparable)y.GetType().GetProperty(this.PropertyName).GetValue(y, null);

        if (this.SortType == AscDesc.Asc)
            return xValue.CompareTo(yValue);

        return yValue.CompareTo(xValue);
    }
    #endregion

    #region IEqualityComparer
    public bool Equals(T x, T y)
    {
        if (typeof(T).GetProperty(PropertyName) == null)
            throw new InvalidOperationException(string.Format("{0} does not contain a property with the name -> \"{1}\"", typeof(T).Name, PropertyName));

        var valuex = x.GetType().GetProperty(PropertyName).GetValue(x, null);
        var valuey = y.GetType().GetProperty(PropertyName).GetValue(y, null);

        if (valuex == null) return valuey == null;

        return valuex.Equals(valuey);
    }

    public int GetHashCode(T obj)
    {
        var info = obj.GetType().GetProperty(PropertyName);
        object value = null;
        if (info != null)
        {
            value = info.GetValue(obj, null);
        }

        return value == null ? 0 : value.GetHashCode();
    }
    #endregion
}

 //Usage
 Product product = new Product();
 Product product2 =new Product();
 EntityComparer<Product> comparer = new EntityComparer<Product>("Propert Name Id Name whatever u want", Asc Or Desc);
 comparer.Compare(product, product2);

如何比较同一类的两个对象？

6 个答案: