具有列表<字符串>作为值的 C# 搜索字典

本文关键字：搜索 字典 列表 字符串 | 更新日期: 2023-09-27 17:55:19

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那些项目。上面的示例，应仅返回"设计器"项。

查询 2：如果上述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，应返回"程序员"、"测试人员"、"设计器"项。如何查询此字典，以便它在问题 1 和 2 中返回所需的结果？

具有列表<字符串>作为值的 C# 搜索字典

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：

  • 设计师
  • 设计师2
 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();
        }

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);
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