我可能会使用正则表达式：

I would probably use a regex:

public static Regex replaceField2 = new Regex(
      "(?<=field2:\").*?(?=\")",
    RegexOptions.IgnoreCase
    | RegexOptions.CultureInvariant
    | RegexOptions.IgnorePatternWhitespace
    | RegexOptions.Compiled
    );

// Replace the matched text in the InputText using the replacement pattern
string result = replaceField2.Replace(InputText,"new value for field2");