string str = "\\u5f00\\u53d1\\u8bed\\u8a00"; 
等价于 string str = @"\\u5f00\\u53d1\\u8bed\\u8a00"; 

string str = "\u5f00\u53d1\u8bed\u8a00"; 错误！！！！

using System;

class Test
{
  static void Main()
  {
    string str  = "\\u5f00\\u53d1\\u8bed\\u8a00"; 
    string str1 = Convert(str);
    Console.WriteLine("[{0}] -> [{1}]", str, str1);
  }
  
  static string Convert(string s)
  {
    return "\u5f00\u53d1\u8bed\u8a00";
  }
}
/* 程序输出:
[\u5f00\u53d1\u8bed\u8a00] -> [开发语言]
*/

using System; 
using System.CodeDom.Compiler; 
using Microsoft.CSharp; 
using System.Reflection;

class Test
{
  static void Main()
  {
    string str  = @"\u5f00\u53d1\r\n\""换行\""\x8bed\u8a00"; 
    string str1 = Convert(str);
    Console.WriteLine("[{0}] -> [{1}]", str, str1);
  }
  
  static string Convert(string s)
  {
    return (new MyString(s)).Parse();
  }
}

sealed class MyString 
{ 
  object instance; 
  MethodInfo method; 
   
  public MyString(string expression) 
  {   
    string className = "MyString"; 
    string methodName = "Parse"; 
    string code = string.Format("using System;sealed class {0}{{public string {1}(){{return \"{2}\";}}}}", 
      className, methodName, expression); 
    CompilerParameters p = new CompilerParameters(); 
    p.GenerateInMemory = true;
    CompilerResults cr = new CSharpCodeProvider().CompileAssemblyFromSource(p, code); 
    if(cr.Errors.Count > 0) 
    { 
      string msg = "MyString(\"" + expression + "\"): \n"; 
      foreach (CompilerError err in cr.Errors) msg += err.ToString() + "\n"; 
      throw new Exception(msg); 
    } 
    instance = cr.CompiledAssembly.CreateInstance(className); 
    method = instance.GetType().GetMethod(methodName); 
  } 
   
  public string Parse() 
  { 
    return (string)method.Invoke(instance, null); 
  } 
} 

/* 程序输出：
[\u5f00\u53d1\r\n\"换行\"\x8bed\u8a00] -> [开发
"换行"语言]
*/

using System; 
using System.CodeDom.Compiler; 
using Microsoft.CSharp; 
using System.Reflection;

class Test
{
  static void Main()
  {
    string s  = @"\x41 B C \u5f00\u53d1\r\n\""换行\""\x8bed\u8a00aa"; 
    string str1 = Convert(s);
    Console.WriteLine("[{0}] -> [{1}]", s, str1);
  }
  
  static string Convert(string s)
  {
    return (new MyString(s)).Parse();
  }
}

sealed class MyString 
{ 
  object instance; 
  MethodInfo method; 
   
  public MyString(string s) 
  {   
    string code = string.Format("sealed class MyString{{public string Parse(){{return \"{0}\";}}}}", s); 
    CompilerParameters p = new CompilerParameters(); 
    p.GenerateInMemory = true;
    CompilerResults cr = new CSharpCodeProvider().CompileAssemblyFromSource(p, code); 
    instance = cr.CompiledAssembly.CreateInstance("MyString"); 
    method = instance.GetType().GetMethod("Parse"); 
  } 
   
  public string Parse() 
  { 
    return (string)method.Invoke(instance, null); 
  } 
} 

/* 程序输出：
[\x41 B C \u5f00\u53d1\r\n\"换行\"\x8bed\u8a00aa] -> [A B C 开发
"换行"语言aa]
*/