c# - 使用 Replace() 从开头删除引号会将它们全部删除

Question

我正在尝试从引号中过滤 csv 文件。这一行奇怪地删除了该行中的所有引号:

之前:"NewClient"Name"

foo = foo.Replace(foo.Substring(0, 1), "");

之后:NewClientName

为什么会这样？ Replace() 方法不应该只删除第一次出现吗？

Answer 1

通常在处理 CSV 时我们加倍引号:

a                 -> "a"
a"b               -> "a""b"
NewClient"Name    -> "NewClient""Name"

要截断这样一个引用，即

"NewClient""Name" -> NewClient"Name

当 "NewClient"Name" 是一个语法错误时，您可以尝试

private static string CutQuotation(string value) {
  if (string.IsNullOrEmpty(value))
    return value;
  else if (!value.Contains('"'))
    return value;

  if (value.Length == 1)
    throw new FormatException("Incorrect quotation format: string can't be of length 1.");
  else if (value[0] != '"')
    throw new FormatException("Incorrect quotation format: string must start with \".");
  else if (value[value.Length - 1] != '"')
    throw new FormatException("Incorrect quotation format: string must end with \".");

  StringBuilder builder = new StringBuilder(value.Length);

  for (int i = 1; i < value.Length - 1; ++i) 
    if (value[i] == '"') 
      if (i == value.Length - 2)
        throw new FormatException("Incorrect quotation format. Dangling \".");
      else if (value[++i] == '"') 
        builder.Append(value[i]);
      else
        throw new FormatException("Incorrect quotation format. Dangling \".");
    else
      builder.Append(value[i]);

  return builder.ToString();
}

如您所见，它不仅仅是单个 Replace() 例程。

测试:

 // abc - no quotation
 Console.WriteLine(CutQuotation("abc")); 
 // abc - simple quotation cut
 Console.WriteLine(CutQuotation("\"abc\"")); 
 // "abc" - double quotation
 Console.WriteLine(CutQuotation("\"\"abc\"\"")); 
 // a"bc - quotation in the middle
 Console.WriteLine(CutQuotation("\"a\"\"bc\""));