在C#中，如何将逗号分隔的键字符串转换为实际值字符串？

有一个名为user的数据库表，假设它具有以下结构和值：

UserKey    UserName
------------------------
1          John Smith
2          Andrew Wright
3          David Morgan
4          Judy Brown
5          ........

在C#中，有人能告诉我如何编写一个函数/方法，将逗号分隔的键字符串转换为用户名字符串（也用逗号分隔）。UserKey和UserName匹配在数据库表user中定义。例如，函数/方法应将字符串“

1,2,3,4”

转换为字符串“John Smith，Andrew Wright，David Morgan，Judy Brown”

多谢各位

您可以尝试将Rdbms表缓存到C#集合中，例如，

字典

：

或通过正则表达式：

  string source = "1,2,3,4";

  string result = Regex.Replace(source, "[0-9]+", match =>
    cache.TryGetValue(match.Value, out var name) ? name : "???");

---

这是你可以做到的。我假设您已经找到了从数据库中按id查找用户的方法（

GetUserFromDb

），所以我只是使用静态数组模拟了这一部分

void Main()
{
    var userKeysString = "1,2,,xx,732,3,4";
    var userNamesString = GetUserNames(userKeysString); 
}

public string GetUserNames(string userKeys)
{
    var keys = userKeys.Split(",").Select(x => int.TryParse(x, out var i) ? i : 0);
    return string.Join(", ", keys.Where(k => k > 0).Select(k => GetUserFromDb(k)?.UserName).Where(u => u != null));
}

private User GetUserFromDb(int userKey)
{
    return AllDbUsers.FirstOrDefault(u => u.UserKey == userKey);
}

public static User[] AllDbUsers = new User[]
{
    new User { UserKey = 1, UserName = "John Smith"},
    new User { UserKey = 2, UserName = "Andrew Wright"},
    new User { UserKey = 3, UserName = "David Morgan"},
    new User { UserKey = 4, UserName = "Judy Brown"},
    new User { UserKey = 5, UserName = "John Doe"},
};

public class User
{
    public int UserKey { get; set; }
    public string UserName { get; set; }
}

---

你能将RDBMS表缓存到C#集合中吗，比如说，

字典

？我不确定，你是在问我是否有权限还是想这样做？我不确定，但我确实想试试。非常感谢德米特里的帮助。我明天会试试，让你知道。非常感谢你的帮助。我明天会试试，然后告诉你。

  string source = "1,2,3,4";

  string result = Regex.Replace(source, "[0-9]+", match =>
    cache.TryGetValue(match.Value, out var name) ? name : "???");

void Main()
{
    var userKeysString = "1,2,,xx,732,3,4";
    var userNamesString = GetUserNames(userKeysString); 
}

public string GetUserNames(string userKeys)
{
    var keys = userKeys.Split(",").Select(x => int.TryParse(x, out var i) ? i : 0);
    return string.Join(", ", keys.Where(k => k > 0).Select(k => GetUserFromDb(k)?.UserName).Where(u => u != null));
}

private User GetUserFromDb(int userKey)
{
    return AllDbUsers.FirstOrDefault(u => u.UserKey == userKey);
}

public static User[] AllDbUsers = new User[]
{
    new User { UserKey = 1, UserName = "John Smith"},
    new User { UserKey = 2, UserName = "Andrew Wright"},
    new User { UserKey = 3, UserName = "David Morgan"},
    new User { UserKey = 4, UserName = "Judy Brown"},
    new User { UserKey = 5, UserName = "John Doe"},
};

public class User
{
    public int UserKey { get; set; }
    public string UserName { get; set; }
}