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C# Linq基本使用方法

2024-07-05 17:51:54   231人阅读

看了不少开发人员写的代码基本上属于LinQ出来很多年，从来没用过，其实还是非常好用的

 

    public void  Foo(){
        Dictionary<int, string> frenchNumbers;
        frenchNumbers = new Dictionary<int, string>();
        frenchNumbers.Add(0, "zero");
        frenchNumbers.Add(1, "one");
        frenchNumbers.Add(2, "two");
        frenchNumbers.Add(3, "three");
        frenchNumbers.Add(4, "four");

        var evenFrenchNumbers =
          from entry in frenchNumbers
          where (entry.Key % 2) == 0
          select entry.Value;
    }

或者

       
enum MyEnum : int
        {
            a,
            b,
            c,
        }

public void foo(){
            var v = Enum.GetNames(typeof(MyEnum)).Select((key, value) =>
            new { key, value }).ToDictionary(x => x.key , x => x.value);
            foreach (var item in v)
            {
                Console.WriteLine(item.Key + "  "+item.Value);
            }
}

再或者

        public static Dictionary<int, string> GetEnumDictionary<T>()
        {
            if (!typeof(T).IsEnum)
                throw new ArgumentException("T is not an Enum type");
            if (Enum.GetUnderlyingType(typeof(T)) != typeof(int))
                throw new ArgumentException("The underlying type of the enum T is not Int32");
            return Enum.GetValues(typeof(T))
                .Cast<T>()
                .ToDictionary(t => (int)(object)t, t => t.ToString());
        }

 


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