[转] Request 接收参数乱码原理解析

 1 public NameValueCollection QueryString
 2 {
 3     get
 4     {
 5         if (this._queryString == null)
 6         {
 7             this._queryString = new HttpValueCollection();
 8             if (this._wr != null)
 9             {
10                 this.FillInQueryStringCollection();//重点代码切入点
11             }
12             this._queryString.MakeReadOnly();
13         }
14         if (this._flags[1])
15         {
16             this._flags.Clear(1);
17             ValidateNameValueCollection(this._queryString, "Request.QueryString");
18         }
19         return this._queryString;
20     }
21 }

 1 private void FillInQueryStringCollection()
 2 {
 3     byte[] queryStringBytes = this.QueryStringBytes;
 4     if (queryStringBytes != null)
 5     {
 6         if (queryStringBytes.Length != 0)
 7         {
 8             this._queryString.FillFromEncodedBytes(queryStringBytes, this.QueryStringEncoding);
 9         }
10     }//上面是对流字节的处理，即文件上传之类的。
11     else if (!string.IsNullOrEmpty(this.QueryStringText))
12     {
13         //下面这句是对普通文件提交的处理:FillFromString是个切入点,编码切入点是：this.QueryStringEncoding
14         this._queryString.FillFromString(this.QueryStringText, true, this.QueryStringEncoding);
15         
16     }
17 }

 1 internal Encoding QueryStringEncoding
 2 {
 3     get
 4     {
 5         Encoding contentEncoding = this.ContentEncoding;
 6         if (!contentEncoding.Equals(Encoding.Unicode))
 7         {
 8             return contentEncoding;
 9         }
10         return Encoding.UTF8;
11     }
12 }
13 //点击进入this.ContentEncoding则为：
14 public Encoding ContentEncoding
15 {
16     get
17     {
18         if (!this._flags[0x20] || (this._encoding == null))
19         {
20             this._encoding = this.GetEncodingFromHeaders();
21             if (this._encoding == null)
22             {
23                 GlobalizationSection globalization = RuntimeConfig.GetLKGConfig(this._context).Globalization;
24                 this._encoding = globalization.RequestEncoding;
25             }
26             this._flags.Set(0x20);
27         }
28         return this._encoding;
29     }
30     set
31     {
32         this._encoding = value;
33         this._flags.Set(0x20);
34     }
35 }

 1 internal void FillFromString(string s, bool urlencoded, Encoding encoding)
 2 {
 3     int num = (s != null) ? s.Length : 0;
 4     for (int i = 0; i < num; i++)
 5     {
 6         int startIndex = i;
 7         int num4 = -1;
 8         while (i < num)
 9         {
10             char ch = s[i];
11             if (ch == ‘=‘)
12             {
13                 if (num4 < 0)
14                 {
15                     num4 = i;
16                 }
17             }
18             else if (ch == ‘&‘)
19             {
20                 break;
21             }
22             i++;
23         }
24         string str = null;
25         string str2 = null;
26         if (num4 >= 0)
27         {
28             str = s.Substring(startIndex, num4 - startIndex);
29             str2 = s.Substring(num4 + 1, (i - num4) - 1);
30         }
31         else
32         {
33             str2 = s.Substring(startIndex, i - startIndex);
34         }
35         if (urlencoded)//外面的传值默认是true,所以会执行以下语句
36         {
37             base.Add(HttpUtility.UrlDecode(str, encoding), HttpUtility.UrlDecode(str2, encoding));
38         }
39         else
40         {
41             base.Add(str, str2);
42         }
43         if ((i == (num - 1)) && (s[i] == ‘&‘))
44         {
45             base.Add(null, string.Empty);
46         }
47     }
48 }

1：系统取默认编码的顺序为：http请求头->globalization配置节点-》默认UTF-8

2：在Url直接输入中文时，不同浏览器处理方式可能不同如：ie不进行编码直接提交，firefox对url进行gb2312编码后提交。

3：对于未编码“中文字符”，使用Request.QueryString时内部调用HttpUtility.UrlDecode后，由gb2312->utf-8时，

如果查不到该中文字符，默认转成"%ufffd"，因此出现不可逆乱码。