Linq if else 条件

Question

如何将以下查询合并为一个查询？ 我认为多个 if 会不必要地增加代码复杂性。

var query = scenario.Where(x => x.ScenarioNumber == ScenarioNumber).Select(x => x).Distinct().ToList();

// Match exception number else return wild card entries.
if(query.Any(x=>x.ExcepNumber == ExcepNumber))
{
    query = query.Where(x => x.ExcepNumber == ExcepNumber).ToList();
}
else
{
   query = query.Where(x => x.ExcepNumber == "**").ToList();
}

// Match regime else return wild card entries.
if (query.Any(x => x.Regime == Regime))
{
     query = query.Where(x => x.Regime == Regime).ToList();
}
else
{
     query = query.Where(x => x.Regime == "**").ToList();
}
finalResponse = query.Select(x => x.TestColumn).Distinct().ToList();

Answer 1

我有一个建议。 您可以将其提取到一个通用方法中，在该方法中您将传递一个选择器 function，它指定用于过滤的属性和您想要比较的 2 个选择（当然还有集合）。

private List<T> EitherFilterOrWildCard<T>(Func<T, string> selector, string compare, string elseCompare, List<T> query)
{
    var temp = query.Where(x => selector(x) == compare);
    
    return temp.Any() ? temp.ToList() : query.Where(x => selector(x) == elseCompare).ToList();
    
}

然后，您的 if 语句将缩小为以下 2 行：

query = EitherFilterOrWildCard<MyClass>(x => x.ExcepNumber, ExcepNumber, "**", query);
query = EitherFilterOrWildCard<MyClass>(x => x.Regime, Regime, "**", query);