Unicode 转 GB2312/UTF8最简单的方式

传统转换方式：

s = @"[\u79FB\u52A8]\u4E00\u5468\u70ED\u95FB\u56DE\u987E\uFF1A\u5F00\u53D1\u5546\u559C\u6B22\u63A8\u8350\u514D\u8D39\u6E38\u620F";
            
Regex reg = new Regex(@"(?i)\\u[a-f0-9]{4}");
Match mat = reg.Match(s);
while (mat.Success)
{
    char c = Convert.ToChar(Convert.ToInt32(mat.Value.Substring(2), 16));
    s = s.Replace(mat.Value, c.ToString());
    mat = reg.Match(s);
}
Console.WriteLine(s);

输出：

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借助于URLDecode转换：

s = @"[\u79FB\u52A8]\u4E00\u5468\u70ED\u95FB\u56DE\u987E\uFF1A\u5F00\u53D1\u5546\u559C\u6B22\u63A8\u8350\u514D\u8D39\u6E38\u620F";

s = System.Web.HttpUtility.UrlDecode(s.Replace(@"\u", "%u"));
Console.WriteLine(s);