循环中创建的分隔字符串

Question

我正在寻找在循环中创建与另一个字符串分隔的字符串的最佳方法.我的意思是,例如,SQL阅读器:

StringBuilder sb = new StringBuilder();
while(reader.Read())
{
  sb.Append(reader[0]);
  sb.Append("<br />");
}
string result = sb.ToString();
result = result.Remove(result.LastIndexOf("<br />")); // <-

或创建SQL查询字符串;

StringBuilder sb = new StringBuilder();
foreach(string v in values)
{
  sb.Append(v);
  sb.Append(",");
}
string query = sb.ToString()
query = query.Remove(query.LastIndexOf(",")); // <-
query = String.Concat("INSERT INTO [foo] ([bar]) VALUES(", query, ")");

这是我发现的最好的:

List<string> list = new List<string>;
while(reader.Read())
{
  list.Add(reader[0]);
}
string result = String.Join("<br />", list.ToArray());

编辑: 我知道StringBuilder,我没有在这里使用它只是为了清楚.我的一般想法不使用Remove/ LastIndexOf!

Answer 1

我不是StringBuilder的粉丝,除非你真的知道你需要担心性能.它产生丑陋的代码.我会这样写的......

private IEnumerable<string> ReadAllStrings(DataReader reader)
{
    while(reader.Read())
        yield return reader[0];
}


String.Join("<br />", ReadAllStrings(reader).ToArray());

如果我做了很多,我可能会考虑一种扩展方法:

public static class Extensions
{
    public static string JoinWith(this IEnumerable<string> strings, string separator)
    {
        return String.Join(separator, strings.ToArray());
    }
}

然后,我的代码看起来像这样:

ReadAllStrings(reader).JoinWith("<br />");

Answer 2

怎么样:

StringBuilder builder;
while (reader.Read())
{
    if( builder == null )
    {
        builder = new StringBuilder(reader[0]);
    }
    else
    {
        builder.Append("<br />");
        builder.Append(reader[0]);
    }
}
string result = builder.ToString();