Question

我已经声明了以下字典，它可以包含10个以上的项目：

 Dictionary<string, List<string>> dictTestdata = new Dictionary<string, List<string>>
        {
            { "k1", new List<string> { "1", "Programmers" }},
            { "k2", new List<string> { "3", "Testers" }},
            { "k3", new List<string> { "", "Designers" }}, 
        };

查询1：我只需要第一个列表项为空的项目。以上示例，应该返回“设计师”＃39;只有项目。

查询2：如果上面字典中的所有第一个列表项都为空，我也想要数据，请参阅下面的声明：

dictTestdata = new Dictionary<string, List<string>>
        {
            { "k1", new List<string> { "", "Programmers" }},
            { "k2", new List<string> { "", "Testers" }},
            { "k3", new List<string> { "", "Designers" }}, 
        };

示例2，应该返回“程序员”，“测试人员”，“设计人员”和“＃39;设计师＆＃39;项目。如何查询此词典，以便它在问题1和2中返回所需的结果？

Answer 1

Dictionary<string, List<string>> dictTestdata = new Dictionary<string, List<string>>
        {
            { "k1", new List<string> { "1", "Programmers" }},
            { "k2", new List<string> { "3", "Testers" }},
            { "k3", new List<string> { "", "Designers" }}, 
            { "k4", new List<string> { "", "Designers2" }}, 
        };

var query = from item in dictTestdata
               where String.IsNullOrWhiteSpace(item.Value.First())
               select item.Value.Where(v => !String.IsNullOrWhiteSpace(v));

query.SelectMany (q => q, (a, b) => b).Dump();

此代码返回：

设计者
Designers2

Answer 2

这是一个可能的解决方案：

Dictionary<string, List<string>> dictTestdata = new Dictionary<string, List<string>>
            {
                { "k1", new List<string> { "1", "Programmers" }},
                { "k2", new List<string> { "3", "Testers" }},
                { "k3", new List<string> { "", "Designers" }}, 
            };

            var result1 = dictTestdata.Where(kvp => string.IsNullOrWhiteSpace(kvp.Value[0]))
                  .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

            dictTestdata = new Dictionary<string, List<string>>
            {
                { "k1", new List<string> { "", "Programmers" }},
                { "k2", new List<string> { "", "Testers" }},
                { "k3", new List<string> { "", "Designers" }}, 
            };

            var result2 = dictTestdata.Where(kvp => string.IsNullOrWhiteSpace(kvp.Value[0]))
                  .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);

Answer 3

 static void Main(string[] args)
        {
            Dictionary<string, List<string>> dictTestdata = new Dictionary<string, List<string>>
        {
            { "k1", new List<string> { "1", "Programmers" }},
            { "k2", new List<string> { "3", "Testers" }},
            { "k3", new List<string> { "", "Designers" }}, 
        };

            var data =   dictTestdata.Values.Where(m => string.IsNullOrEmpty(m.ElementAtOrDefault(0)));
            foreach (List<string> item in data)
            {
                Console.WriteLine(item.ElementAtOrDefault(1));
            }

            dictTestdata = new Dictionary<string, List<string>>
        {
            { "k1", new List<string> { "", "Programmers" }},
            { "k2", new List<string> { "", "Testers" }},
            { "k3", new List<string> { "", "Designers" }}, 
        };
             data = dictTestdata.Values.Where(m => string.IsNullOrEmpty(m.ElementAtOrDefault(0)));
            foreach (List<string> item in data)
            {
                Console.WriteLine(item.ElementAtOrDefault(1));
            }
            Console.Read();
        }

C＃搜索具有List <string>作为值的字典

3 个答案: