private string getGUID()
    {
        System.Guid guid = new Guid();
        guid = Guid.NewGuid();
        string str = guid.ToString();
        return str;
    }

随机生成如下字符串：
e92b8e30-a6e5-41f6-a6b9-188230a23dd2

格式说明：

System.Guid.NewGuid().ToString(format)  
   
格式说明符            
返回值的格式    
   
N 32位：
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
如：e92b8e30a6e541f6a6b9188230a23dd2
     
D 由连字符分隔的32位数字：                                    
xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
如：e92b8e30-a6e5-41f6-a6b9-188230a23dd2
     
B 括在大括号中、由连字符分隔的32位数字：      
{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
如：{e92b8e30-a6e5-41f6-a6b9-188230a23dd2}
     
P 括在圆括号中、由连字符分隔的32位数字：        
(xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)
如：(e92b8e30-a6e5-41f6-a6b9-188230a23dd2)