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HttpRequest的QueryString屬性 的一點認識

 更新時間：2012年11月06日 17:03:38   作者：  
我們開發(fā)asp.net程序獲取QueryString時，經常性的遇到一些url編碼問題
如：


當然我們一般都是按照提示來把framework版本設置2.0來解決。為什么可以這么解決了，還有沒有其它的解決方法了。
先讓我們看看QueryString的源代碼吧：
復制代碼 代碼如下:

public NameValueCollection QueryString
{
get
{
if (this._queryString == null)
{
this._queryString = new HttpValueCollection();
if (this._wr != null)
{
this.FillInQueryStringCollection();
}
this._queryString.MakeReadOnly();
}
if (this._flags[1])
{
this._flags.Clear(1);
this.ValidateNameValueCollection(this._queryString, RequestValidationSource.QueryString);
}
return this._queryString;
}
}
private void FillInQueryStringCollection()
{
byte[] queryStringBytes = this.QueryStringBytes;
if (queryStringBytes != null)
{
if (queryStringBytes.Length != 0)
{
this._queryString.FillFromEncodedBytes(queryStringBytes, this.QueryStringEncoding);
}
}
else if (!string.IsNullOrEmpty(this.QueryStringText))
{
this._queryString.FillFromString(this.QueryStringText, true, this.QueryStringEncoding);
}
}

　　先讓我們插入一點 那就是QueryString默認已經做了url解碼。 其中HttpValueCollection的 FillFromEncodedBytes方法如下
復制代碼 代碼如下:

internal void FillFromEncodedBytes(byte[] bytes, Encoding encoding)
{
int num = (bytes != null) ? bytes.Length : 0;
for (int i = 0; i < num; i++)
{
string str;
string str2;
this.ThrowIfMaxHttpCollectionKeysExceeded();
int offset = i;
int num4 = -1;
while (i < num)
{
byte num5 = bytes[i];
if (num5 == 0x3d)
{
if (num4 < 0)
{
num4 = i;
}
}
else if (num5 == 0x26)
{
break;
}
i++;
}
if (num4 >= 0)
{
str = HttpUtility.UrlDecode(bytes, offset, num4 - offset, encoding);
str2 = HttpUtility.UrlDecode(bytes, num4 + 1, (i - num4) - 1, encoding);
}
else
{
str = null;
str2 = HttpUtility.UrlDecode(bytes, offset, i - offset, encoding);
}
base.Add(str, str2);
if ((i == (num - 1)) && (bytes[i] == 0x26))
{
base.Add(null, string.Empty);
}
}
}

從這里我們可以看到QueryString已經為我們做了解碼工作，我們不需要寫成 HttpUtility.HtmlDecode(Request.QueryString["xxx"])而是直接寫成Request.QueryString["xxx"]就ok了。
現(xiàn)在讓我們來看看你QueryString的驗證，在代碼中有
復制代碼 代碼如下:

if (this._flags[1])
{
this._flags.Clear(1);
this.ValidateNameValueCollection(this._queryString, RequestValidationSource.QueryString);
}

一看this.ValidateNameValueCollection這個方法名稱就知道是干什么的了，驗證QueryString數(shù)據(jù)；那么在什么情況下驗證的了？
讓我們看看this._flags[1]在什么地方設置的：
復制代碼 代碼如下:

public void ValidateInput()
{
if (!this._flags[0x8000])
{
this._flags.Set(0x8000);
this._flags.Set(1);
this._flags.Set(2);
this._flags.Set(4);
this._flags.Set(0x40);
this._flags.Set(0x80);
this._flags.Set(0x100);
this._flags.Set(0x200);
this._flags.Set(8);
}
}

　　而該方法在ValidateInputIfRequiredByConfig中調用，調用代碼
復制代碼 代碼如下:

internal void ValidateInputIfRequiredByConfig()
{
.........
if (httpRuntime.RequestValidationMode >= VersionUtil.Framework40)
{
this.ValidateInput();
}
}

我想現(xiàn)在大家都應該明白為什么錯題提示讓我們把framework改為2.0了吧。應為在4.0后才驗證。這種解決問題的方法是關閉驗證，那么我們是否可以改變默認的驗證規(guī)則了？
讓我們看看ValidateNameValueCollection
復制代碼 代碼如下:

private void ValidateNameValueCollection(NameValueCollection nvc, RequestValidationSource requestCollection)
{
int count = nvc.Count;
for (int i = 0; i < count; i++)
{
string key = nvc.GetKey(i);
if ((key == null) || !key.StartsWith("__", StringComparison.Ordinal))
{
string str2 = nvc.Get(i);
if (!string.IsNullOrEmpty(str2))
{
this.ValidateString(str2, key, requestCollection);
}
}
}
}
private void ValidateString(string value, string collectionKey, RequestValidationSource requestCollection)
{
int num;
value = RemoveNullCharacters(value);
if (!RequestValidator.Current.IsValidRequestString(this.Context, value, requestCollection, collectionKey, out num))
{
string str = collectionKey + "=\"";
int startIndex = num - 10;
if (startIndex <= 0)
{
startIndex = 0;
}
else
{
str = str + "...";
}
int length = num + 20;
if (length >= value.Length)
{
length = value.Length;
str = str + value.Substring(startIndex, length - startIndex) + "\"";
}
else
{
str = str + value.Substring(startIndex, length - startIndex) + "...\"";
}
string requestValidationSourceName = GetRequestValidationSourceName(requestCollection);
throw new HttpRequestValidationException(SR.GetString("Dangerous_input_detected", new object[] { requestValidationSourceName, str }));
}
}
　　
　　哦？原來一切都明白了，驗證是在RequestValidator做的。
復制代碼 代碼如下:

public class RequestValidator
{
// Fields
private static RequestValidator _customValidator;
private static readonly Lazy<RequestValidator> _customValidatorResolver = new Lazy<RequestValidator>(new Func<RequestValidator>(RequestValidator.GetCustomValidatorFromConfig));
// Methods
private static RequestValidator GetCustomValidatorFromConfig()
{
HttpRuntimeSection httpRuntime = RuntimeConfig.GetAppConfig().HttpRuntime;
Type userBaseType = ConfigUtil.GetType(httpRuntime.RequestValidationType, "requestValidationType", httpRuntime);
ConfigUtil.CheckBaseType(typeof(RequestValidator), userBaseType, "requestValidationType", httpRuntime);
return (RequestValidator) HttpRuntime.CreatePublicInstance(userBaseType);
}
internal static void InitializeOnFirstRequest()
{
RequestValidator local1 = _customValidatorResolver.Value;
}
private static bool IsAtoZ(char c)
{
return (((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z')));
}
protected internal virtual bool IsValidRequestString(HttpContext context, string value, RequestValidationSource requestValidationSource, string collectionKey, out int validationFailureIndex)
{
if (requestValidationSource == RequestValidationSource.Headers)
{
validationFailureIndex = 0;
return true;
}
return !CrossSiteScriptingValidation.IsDangerousString(value, out validationFailureIndex);
}
// Properties
public static RequestValidator Current
{
get
{
if (_customValidator == null)
{
_customValidator = _customValidatorResolver.Value;
}
return _customValidator;
}
set
{
if (value == null)
{
throw new ArgumentNullException("value");
}
_customValidator = value;
}
}
}　

主要的驗證方法還是在CrossSiteScriptingValidation.IsDangerousString(value, out validationFailureIndex);而CrossSiteScriptingValidation是一個內部類，無法修改。
讓我們看看CrossSiteScriptingValidation類大代碼把
復制代碼 代碼如下:

internal static class CrossSiteScriptingValidation
{
// Fields
private static char[] startingChars = new char[] { '<', '&' };
// Methods
private static bool IsAtoZ(char c)
{
return (((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z')));
}
internal static bool IsDangerousString(string s, out int matchIndex)
{
matchIndex = 0;
int startIndex = 0;
while (true)
{
int num2 = s.IndexOfAny(startingChars, startIndex);
if (num2 < 0)
{
return false;
}
if (num2 == (s.Length - 1))
{
return false;
}
matchIndex = num2;
char ch = s[num2];
if (ch != '&')
{
if ((ch == '<') && ((IsAtoZ(s[num2 + 1]) || (s[num2 + 1] == '!')) || ((s[num2 + 1] == '/') || (s[num2 + 1] == '?'))))
{
return true;
}
}
else if (s[num2 + 1] == '#')
{
return true;
}
startIndex = num2 + 1;
}
}
internal static bool IsDangerousUrl(string s)
{
if (string.IsNullOrEmpty(s))
{
return false;
}
s = s.Trim();
int length = s.Length;
if (((((length > 4) && ((s[0] == 'h') || (s[0] == 'H'))) && ((s[1] == 't') || (s[1] == 'T'))) && (((s[2] == 't') || (s[2] == 'T')) && ((s[3] == 'p') || (s[3] == 'P')))) && ((s[4] == ':') || (((length > 5) && ((s[4] == 's') || (s[4] == 'S'))) && (s[5] == ':'))))
{
return false;
}
if (s.IndexOf(':') == -1)
{
return false;
}
return true;
}
internal static bool IsValidJavascriptId(string id)
{
if (!string.IsNullOrEmpty(id))
{
return CodeGenerator.IsValidLanguageIndependentIdentifier(id);
}
return true;
}
}

　　結果我們發(fā)現(xiàn)&# <! </ <? <[a-zA-z] 這些情況驗證都是通不過的。
所以我們只需要重寫RequestValidator就可以了。
例如我們現(xiàn)在需要處理我們現(xiàn)在需要過濾QueryString中k=&...的情況
復制代碼 代碼如下:

public class CustRequestValidator : RequestValidator
{
protected override bool IsValidRequestString(HttpContext context, string value, RequestValidationSource requestValidationSource, string collectionKey, out int validationFailureIndex)
{
validationFailureIndex = 0;
//我們現(xiàn)在需要過濾QueryString中k=&...的情況
if (requestValidationSource == RequestValidationSource.QueryString&&collectionKey.Equals("k")&& value.StartsWith("&"))
{
return true;
}
return base.IsValidRequestString(context, value, requestValidationSource, collectionKey, out validationFailureIndex);
}
}
　　<httpRuntime requestValidationType="MvcApp.CustRequestValidator"/>

個人在這里只是提供一個思想，歡迎大家拍磚！

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