如何在linq中使用TryParse

问题描述

        else{ 
            if(a.Item2 == ">"){
                    result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && double.TryParse(y.Value,out double res) == double.TryParse(a.Item3,out double res1)));
                //result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && Convert.Todouble(y.Value) > Convert.Todouble(a.Item3)));    
            }
            else if(a.Item2 == "<")
                result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && Convert.Todouble(y.Value) < Convert.Todouble(a.Item3)));
            else if(a.Item2 == "<=")
                result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && Convert.Todouble(y.Value) <= Convert.Todouble(a.Item3)));
            else if(a.Item2 == ">=")
                result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && Convert.Todouble(y.Value) >= Convert.Todouble(a.Item3)));
            else if(a.Item2 == "==")
                result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && Convert.Todouble(y.Value) == Convert.Todouble(a.Item3)));
            else if(a.Item2 == "!=")
                result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 && Convert.Todouble(y.Value) != Convert.Todouble(a.Item3)));
            else
                 throw new Exception("Comparison operator not found");          
        }

在上述代码情况下如何使用double.TryParse代替Convert.Todouble，因为我不知道如何使用out值进行比较。我要使用TryParse，因为出现以下错误消息：

输入字符串的格式不正确

如何在当前的Senario中实现这一目标？

解决方法

这有点冗长，但是假设您只想返回可以将值解析为double的行：

result = dict.Where(x => x.Value.Any(y => y.Key == a.Item1 
     && double.TryParse(y.Value,out double res)  // Value can be parsed
     && double.TryParse(a.Item3,out double res1) // Item3 can be parsed
     && res == res1)); // the 2 parsed results match