从名称匹配的列表列中选择值

Question

我有一个包含不同列的列表，Name和Bitrate。

public class VideoQuality
{
    public string Name { get; set; }
    public string Bitrate { get; set; }
}

public List<VideoQuality> quality = new List<VideoQuality>()
{
     new VideoQuality() { Name = "High",   Bitrate = "5000K" },
     new VideoQuality() { Name = "Medium", Bitrate = "2500K" },
     new VideoQuality() { Name = "Low",    Bitrate = "500K" },
};

如何从列表中选择Bitrate是High

类似于：

if (selectedQuality == "High")
{
    // Select High Bitrate from List
    string vBitrate = quality.Select(x => x.Bitrate)
                             .Where(Name = "High");
}

vBitrate应该等于5000K。

Answer 1

首先要过滤，然后选择：

var result = quality.Where(x => x.Name == "High")
                    .Select(x => x.Bitrate); //IEnumerable<string>

在查询语法中：

var result = from x in quality
             where x.Name == "High"
             select x.Bitrate; //IEnumerable<string>

注意，在任何情况下，如果结果是IEnumerable<string>而不是单个项的话。如果您只想要一个项目，那么使用FirstOrDefault/First/Single，SingleOrDefault

var result = quality.FirstOrDefault(x => x.Name == "High")?.Bitrate; //string

有关不同方法之间的差异，请参阅文档和https://stackoverflow.com/q/1745691/6400526。

Answer 2

如果您期望返回最多一个值，我建议使用FirstOrDefault

string vBitrate = quality
  .FirstOrDefault(item => item.Name == "High")
 ?.BitRate;