比较通用方法中的两个值c#

Question

我认为我的代码可以自我解释我想要实现的目标:

private bool Comparison<T>(T operatorOne, T operatorTwo, string operand)
    {
        switch (operand.ToLower())
        {
            case "=":
                return operatorOne.Equals(operatorTwo);
            case "<":
                return operatorOne < operatorTwo;
            case ">":
                return operatorOne > operatorTwo;
            case "contains":
                return operatorOne.ToString().Contains(operatorTwo.ToString());
            default:
                return false;
        }
    }

它给了我错误:

Error   16  Operator '>','<' cannot be applied to operands of type 'T' and 'T'

我需要一个可以比较字符串,Int,Double,chars的方法.注意:排除将为>或<check>传递字符串的条件或将为"包含"检查发送Int

Answer 1

你可以Comparer<T>.Default.Compare(operatorOne, operatorTwo)用来比较.请注意,如果T没有实现IComparable和IComparable<T>,Comparer<T>.Default.Compare抛出异常.

要确保T实现IComparable,您可以添加where T: IComparable约束.(它将排除实现的类IComparable<T>,但不包括 IComparable.仍然可以接受,因为许多类实现IComparable<T>,也实现IComparable.)

private bool Comparison<T>(T operatorOne, T operatorTwo, string operand)
    where T: IComparable
{
    switch(operand.ToLower())
    {
        case "=":
            return Comparer<T>.Default.Compare(operatorOne, operatorTwo) == 0;
        case "<":
            return Comparer<T>.Default.Compare(operatorOne, operatorTwo) < 0;
        case ">":
            return Comparer<T>.Default.Compare(operatorOne, operatorTwo) > 0;
        case "contains":
            return operatorOne.ToString().Contains(operatorTwo.ToString());
        default:
            return false;
    }
}

PS

正如Servy建议的那样,您也可以IComparer作为额外参数传递给函数.它将允许涵盖既不实现IComparable也不实现的类型IComparable<T>,因此Comparer<T>.Default不适用于它们.

此外,信用去@TimothyShields,谁建议Comparer<T>.Default.