如何从名称集合构建字符串

Question

我有一组名字，我需要将它们组合成逗号分隔的字符串。

生成的字符串需要遵循正确的语法。

如果集合包含一个名称，则输出应该只是该名称：

John

如果集合包含两个名称，那么输出应该用单词“and”分隔：

John and Mary

如果集合包含三个或更多名称，则输出应以逗号分隔，并且姓氏前面应包含单词“and”：

John, Mary, and Jane

这是我提出的代码。它不是很优雅，我想知道在C＃中是否有更好的方法来实现这一点（4.0可以）。

List<string> firstNames = new List<string>();
firstNames.Add("John");
firstNames.Add("Mary");
firstNames.Add("Jane");

string names = string.Empty;
for (int i = 0; i < firstNames.Count; i++)
{
    if (i == 1 && firstNames.Count == 2)
    {
        names += " and ";
    }
    else if (firstNames.Count > 2 && i > 0 && i != firstNames.Count - 1)
    {
        names += ", ";
    }
    else if (i != 0 && i == firstNames.Count - 1)
    {
        names += ", and ";
    }

    names += firstNames[i];
}

Answer 1

我认为它不会比以下更优雅：

 if (names.Count == 0)
     return "";

 if (names.Count == 1)
     return names[0];

 if (names.Count == 2)
     return names[0] + " and " + names[1];

 return String.Join(", ", names.Take(names.Count - 1)) +
     ", and "  + names[names.Count - 1];

我没有编译这个，但我想你明白了。

编辑：更短，但不太可读：

 if (names.Count <= 2)
     return String.Join(" and ", names);

 return String.Join(", ", names.Take(names.Count - 1)) + 
     ", and "  + names[names.Count - 1];

Answer 2

我会做这样的事情：

using System;
using System.Collections.Generic;

class Program {

    static void Main(string[] args) {
        List<string> firstNames = new List<string>();
        firstNames.Add("John");
        firstNames.Add("Mary");
        firstNames.Add("Jane");
        Console.WriteLine(NamesString(firstNames));
    }

    static string NamesString(List<string> firstNames) {
        switch (firstNames.Count) {
        case 0:
            return string.Empty;
        case 1:
            return firstNames[0];
        case 2:
            return string.Join(" and ", firstNames.ToArray());
        default:
            return string.Format("{0} and {1}",
                string.Join(", ", firstNames.ToArray(), 0, firstNames.Count - 1),
                firstNames[firstNames.Count - 1]);
        }
    }
}

编辑：实际应该是

        default:
            return string.Format("{0}, and {1}",

如果您想在最后一个“和”之前使用逗号。

Answer 3

        string a=string.Join(",", FirstNames.ToArray());
        if (FirstNames.Count == 1)
            a.Replace(",", "");
        else if (FirstNames.Count == 2)
            a.Replace(",", " and ");
        else
        {
            int i = a.LastIndexOf(",");
            a = a.Substring(1, i) + a.Substring(i).Replace(",", " and ");
        }

Answer 4

    static string JoinNames(List<string> firstNames)
    {
        int count = firstNames.Count;
        if(count == 1)
        {
            return firstNames[0];
        }

        if(count > 1)
        {
            return string.Join(", ", firstNames.Take(count - 1).ToArray()) + " and " + firstNames[count - 1];
        }
        return string.Empty;
    }

Answer 5

List<string> firstNames = new List<string>();
firstNames.Add("John");
firstNames.Add("Mary");
firstNames.Add("Jane");

StringBuilder names = new StringBuilder();
for (int i = 0; i < firstNames.Count; i++)
{
    if((i-1) == firstNames.Count && names.length > 0)
         names.AppendFormat(" and {0}", names[i]);
    else if(names.length > 0)
         names.AppendFormat(", {0}", names[i]);    
}
return names.ToString();

我认为这是最好的方式。

Answer 6

List<string> firstNames = new List<string>();
firstNames.Add("John");
firstNames.Add("Mary");
firstNames.Add("Jane");
int cnt = 0;
string names = string.Empty;
while (cnt<=firstName.Count)
{
    string separator = "";

    if (firstName.Count - cnt > 1) separator = ", ";

    else if (firstName.Count - cnt = 1) separator = ", and ";

    else separator = "";

    names += firstName[cnt] + separator;

    cnt += 1;


}

Answer 7

这是一个有趣的解决方案：

        //code
        List<string> firstNames = new List<string>();
        firstNames.Add("John");
        firstNames.Add("Mary");
        firstNames.Add("Jane");

        StringBuilder sb = new StringBuilder();
        firstNames.Take(firstNames.Count - 1).ToList().ForEach(fn => AddString(fn, sb));
        sb.Append(", and " + firstNames.Last());

    //Helper Function
    public void AddString (string fn, StringBuilder sb)
    {
        if (sb.Length != 0)
        {
            sb.Append(", ");
        }
        sb.Append(fn);
    }

Answer 8

尝试使用此尺寸：

            List<string> firstNames = new List<string>();
            firstNames.Add("John");
            firstNames.Add("Mary");
            firstNames.Add("Jane");

            // Only do this if there is more than one name
            if (firstNames.Count > 1)
            {
                string separator = ", ";

                // Join the names, using ", " as a separator
                string names = String.Join(seperator, firstNames.ToArray());

                // Insert "and" before the last comma
                names = names.Insert(names.LastIndexOf(separator), ", and ");

                // Remove the last comma
                names = names.Remove(names.LastIndexOf(separator), separator.Length);
            }

Answer 9

var a = String.Join(", ", firstNames.Skip(1).ToArray()) + (firstNames.Count < 2 ? "" : ", and ") + firstNames.Take(1).FirstOrDefault();

Answer 10

我更喜欢最具可读性的代码。在列表中添加名称时，您需要考虑4个标点符号，因此请将其拼写出来。

static string Combine(List<string> names)
{
    var sb = new StringBuilder();
    for (int i = 0; i < names.Count; i++)
    {
        if (i == 0) //at start of a list
            {}

        else if (i < names.Count - 1) //in middle of list
            sb.Append(", ");

        else if( names.Count == 2 ) //at end of a list with 2 elements
            sb.Append(" and ");

        else //at end of a list with 3 or more elements
            sb.Append(", and ");

        sb.Append(names[i]);
    }
    return sb.ToString();
}

Answer 11

public string Combine(List<string> names)
{
    if (names == null || names.Count == 0)
    {
        return string.Empty;
    }

    var sb = new StringBuilder();
    sb.Append(names[0]);

    //Handle Special Case of 2 names
    if (names.Count == 2)
    {
        sb.Append(" and " + names[1])
        return sb.ToString();
    }

    for (int i = 1; i < names.Count; i++)          
    {
        if (i == (names.Count -1))
        { 
            sb.Append(", and " + names[i]);
        }
        else
        {
            sb.Append(", " + names[i]);
        }
    }

    return sb.ToString(); 
}