c# - 改进代码 : Compare 2 list of elements

Question

抱歉新手问题，但我是编程新手..

我想检查 listOfDifferentTypes 中是否已经只有一个 TypeA 元素。我有以下代码:

     public void CheckType ( Object param)
     {
            if ( param is TypeA )
            {
                int i = 0;
                TypeA paramToCheck = ( TypeA ) param;

                foreach ( var paramB in listOfDifferentTypes )
                {
                    if ( paramB is TypeA )
                    {
                        var paramInList = ( TypeA ) paramB;
                        if ( paramToCheck.ID == paramInList.ID )
                        {
                            i++;
                        }
                    }
                }
                if ( i > 1 )
                {
                    paramToCheck.m_Error = "ErrorText";
                }    
            }
    }

我认为这不是很干净的解决方案。这段代码可以改进/优化吗？

Answer 1

你可以为此使用 LINQ :) 它看起来不错:

//Checks for string - resplace <string> with <some type> for other types
private bool moreThanOne(List<object> differentTypes)
{
    return differentTypes.OfType<string>().Count() > 1;
}

用法:

List<object> listOfDifferentTypes = new List<object> { "string", 13, 52, "string", 54.3f };

var res = moreThanOne(listOfDifferentTypes);

我看到您还检查某种 ID，然后试试这个:

已更新以执行您的代码正在执行的操作

更新:将 .Count() 替换为 .Skip(1).Any()，因此如果找到超过 1 个，它将停止 :)

private void CheckType(object param, List<object> differentTypes)
{
    var paramToCheck = param as TypeA;

    if (paramToCheck == null) return;

    var res = differentTypes.OfType<TypeA>().Where(t => t.ID == paramToCheck.ID).Skip(1).Any();

    if (res) paramToCheck.m_Error = "error text";
}

正如我所做的，您可以替换:

if (param is TypeA)
{
    TypeA paramToCheck = (TypeA) param;
    ... Do something

与:

TypeA paramToCheck = param as TypeA; //Returns null if not a TypeA
if (param == null) return;

... Do something

有点快:)