HttpWebRequest-header設置

在HttpWebRequest中，有一些header為限制級的，對於這些header，你不能直接來通過headers.Add方法來添加，比如Host、Connection、User-Agent、Referer、Range、Content-Type、Content-Length、Expect、Proxy-Connection、If-Modified-Since等header. 這些header都是通過屬性來設置的 。

添加的具體步驟如下

1，測試是否能夠為請求設置指定的 HTTP 標頭；

WebHeaderCollection.IsRestricted(string headerName, bool response);

2, 添加頭字符串；

WebHeaderCollection headers = request.Headers;
headers.Add("Accept-Language: en-us;q=0.5,en;q=0.3");

 

參考源碼：

internal class HeaderInfo
{
    // Fields
    internal readonly bool AllowMultiValues;
    internal readonly string HeaderName;
    internal readonly bool IsRequestRestricted;
    internal readonly bool IsResponseRestricted;
    internal readonly HeaderParser Parser;

    // Methods
    internal HeaderInfo(string name, bool requestRestricted, bool responseRestricted, bool multi, HeaderParser p)
    {
        this.HeaderName = name;
        this.IsRequestRestricted = requestRestricted;
        this.IsResponseRestricted = responseRestricted;
        this.Parser = p;
        this.AllowMultiValues = multi;
    }
}


internal class HeaderInfoTable
{
    // Fields
    private static Hashtable HeaderHashTable;
    private static HeaderParser MultiParser = new HeaderParser(HeaderInfoTable.ParseMultiValue);
    private static HeaderParser SingleParser = new HeaderParser(HeaderInfoTable.ParseSingleValue);
    private static HeaderInfo UnknownHeaderInfo = new HeaderInfo(string.Empty, false, false, false, SingleParser);

    // Methods
    static HeaderInfoTable()
    {
        HeaderInfo[] infoArray = new HeaderInfo[] { 
            new HeaderInfo("Age", false, false, false, SingleParser),
            new HeaderInfo("Allow", false, false, true, MultiParser),
            new HeaderInfo("Accept", true, false, true, MultiParser), 
            new HeaderInfo("Authorization", false, false, true, MultiParser), 
            new HeaderInfo("Accept-Ranges", false, false, true, MultiParser), 
            new HeaderInfo("Accept-Charset", false, false, true, MultiParser),
            new HeaderInfo("Accept-Encoding", false, false, true, MultiParser), 
            new HeaderInfo("Accept-Language", false, false, true, MultiParser),
            new HeaderInfo("Cookie", false, false, true, MultiParser), 
            new HeaderInfo("Connection", true, false, true, MultiParser), 
            new HeaderInfo("Content-MD5", false, false, false, SingleParser), 
            new HeaderInfo("Content-Type", true, false, false, SingleParser),
            new HeaderInfo("Cache-Control", false, false, true, MultiParser), 
            new HeaderInfo("Content-Range", false, false, false, SingleParser),
            new HeaderInfo("Content-Length", true, true, false, SingleParser), 
            new HeaderInfo("Content-Encoding", false, false, true, MultiParser), 
            new HeaderInfo("Content-Language", false, false, true, MultiParser), 
            new HeaderInfo("Content-Location", false, false, false, SingleParser), 
            new HeaderInfo("Date", true, false, false, SingleParser), 
            new HeaderInfo("ETag", false, false, false, SingleParser),
            new HeaderInfo("Expect", true, false, true, MultiParser),
            new HeaderInfo("Expires", false, false, false, SingleParser),
            new HeaderInfo("From", false, false, false, SingleParser), 
            new HeaderInfo("Host", true, false, false, SingleParser), 
            new HeaderInfo("If-Match", false, false, true, MultiParser),
            new HeaderInfo("If-Range", false, false, false, SingleParser),
            new HeaderInfo("If-None-Match", false, false, true, MultiParser),
            new HeaderInfo("If-Modified-Since", true, false, false, SingleParser), 
            new HeaderInfo("If-Unmodified-Since", false, false, false, SingleParser),
            new HeaderInfo("Keep-Alive", false, true, false, SingleParser), 
            new HeaderInfo("Location", false, false, false, SingleParser), 
            new HeaderInfo("Last-Modified", false, false, false, SingleParser), 
            new HeaderInfo("Max-Forwards", false, false, false, SingleParser), 
            new HeaderInfo("Pragma", false, false, true, MultiParser), 
            new HeaderInfo("Proxy-Authenticate", false, false, true, MultiParser), 
            new HeaderInfo("Proxy-Authorization", false, false, true, MultiParser), 
            new HeaderInfo("Proxy-Connection", true, false, true, MultiParser), 
            new HeaderInfo("Range", true, false, true, MultiParser), 
            new HeaderInfo("Referer", true, false, false, SingleParser), 
            new HeaderInfo("Retry-After", false, false, false, SingleParser), 
            new HeaderInfo("Server", false, false, false, SingleParser), 
            new HeaderInfo("Set-Cookie", false, false, true, MultiParser),
            new HeaderInfo("Set-Cookie2", false, false, true, MultiParser), 
            new HeaderInfo("TE", false, false, true, MultiParser), 
            new HeaderInfo("Trailer", false, false, true, MultiParser), 
            new HeaderInfo("Transfer-Encoding", true, true, true, MultiParser), 
            new HeaderInfo("Upgrade", false, false, true, MultiParser), 
            new HeaderInfo("User-Agent", true, false, false, SingleParser), 
            new HeaderInfo("Via", false, false, true, MultiParser), 
            new HeaderInfo("Vary", false, false, true, MultiParser),
            new HeaderInfo("Warning", false, false, true, MultiParser), 
            new HeaderInfo("WWW-Authenticate", false, true, true, SingleParser)
         };
        HeaderHashTable = new Hashtable(infoArray.Length * 2, CaseInsensitiveAscii.StaticInstance);
        for (int i = 0; i < infoArray.Length; i++)
        {
            HeaderHashTable[infoArray[i].HeaderName] = infoArray[i];
        }
    }

    private static string[] ParseMultiValue(string value)
    {
        StringCollection strings = new StringCollection();
        bool flag = false;
        int length = 0;
        char[] chArray = new char[value.Length];
        for (int i = 0; i < value.Length; i++)
        {
            if (value[i] == '"')
            {
                flag = !flag;
            }
            else if ((value[i] == ',') && !flag)
            {
                string str = new string(chArray, 0, length);
                strings.Add(str.Trim());
                length = 0;
                continue;
            }
            chArray[length++] = value[i];
        }
        if (length != 0)
        {
            strings.Add(new string(chArray, 0, length).Trim());
        }
        string[] array = new string[strings.Count];
        strings.CopyTo(array, 0);
        return array;
    }

    private static string[] ParseSingleValue(string value)
    {
        return new string[] { value };
    }

    // Properties
    internal HeaderInfo this[string name]
    {
        get
        {
            HeaderInfo info = (HeaderInfo) HeaderHashTable[name];
            if (info == null)
            {
                return UnknownHeaderInfo;
            }
            return info;
        }
    }
}

 
Collapse Methods