定义一个类来获取项目中的页面环境信息。

在做B/S项目时，经常需要获取一些URL发送过来的参数来实例化一些对象，而一些项目要是比较复杂，那他的各种URL所包含的ID 就会很丰富，如果在每个页面都要获取不同的ID ，那每个页面都要写很多代码，如
if(Request.QueryString["trialInfo_id"]!=null && Request.QueryString["trialInfo_id"].ToString() !="")
trialInfo_id = Request.QueryString["trialInfo_id"].ToString();

这样的语句，而且获取到参数之后，还要判断这个参数的有效性，或者还要从这个参数去获取其他的环境变量，而如果每个页面都写代码去实现，那必然导致代码过于重复，复用性不高。 读了ASP。NET FORUMS 的代码后，了解到里头的解决方案就是 获取当前的 HttpContext.Current 信息，并且给予扩展，把项目中可能用到的参数都写到里面去，当然可以把一些判断逻辑也写到里头。代码如：

using System;
using System.Web;
using System.Collections;
using AspNetForums.Enumerations;

namespace AspNetForums.Components {

public class ForumContext {
int forumID = -1;
int messageID = -1;
int forumGroupID = -1;
int postID = -1;
int threadID = -1;
int userID = -1;
string userName = "";
int pageIndex = -1;
int roleID = -1;
string queryText = "";
string returnUrl = "";
string checkGuid = "";
bool isElite=false ; // fzuray 是否浏览精华
bool isSubject = false; //fzuray 是否为专题

HttpContext context;
DateTime requestStartTime = DateTime.Now;

public ForumContext() {

context = HttpContext.Current;

if (context == null)
return;

// Read common values we expect to find on the QS
//
postID = GetIntFromQueryString(context, "PostID");
forumID = GetIntFromQueryString(context, "ForumID");
forumGroupID = GetIntFromQueryString(context, "ForumGroupID");
userID = GetIntFromQueryString(context, "UserID");
messageID = GetIntFromQueryString(context, "MessageID");
pageIndex = GetIntFromQueryString(context, "PageIndex");
roleID = GetIntFromQueryString(context, "RoleID");
queryText = context.Request.QueryString["q"];
returnUrl = context.Request.QueryString["returnUrl"];
checkGuid = context.Request.QueryString["guid"];
if(context.Request.QueryString["IsElite"]!=null && context.Request.QueryString["isElite"].ToString()=="True") isElite=true; // fzuray 精华
if(context.Request.QueryString["IsSubject"]!=null && context.Request.QueryString["IsSubject"].ToString()=="True") isElite=true; // fzuray 专题
}

public static ForumContext Current {
get {
if (HttpContext.Current == null)
return new ForumContext();

return (ForumContext) HttpContext.Current.Items["ForumContext"];
}

}

// *********************************************************************
// GetIntFromQueryString
//
/// <summary>
/// Retrieves a value from the query string and returns it as an int.
/// </summary>
// ***********************************************************************/
public static int GetIntFromQueryString(HttpContext context, string key) {
int returnValue = -1;
string queryStringValue;

// Attempt to get the value from the query string
//
queryStringValue = context.Request.QueryString[key];

// If we didn't find anything, just return
//
if (queryStringValue == null)
return returnValue;

// Found a value, attempt to conver to integer
//
try {

// Special case if we find a # in the value
//
if (queryStringValue.IndexOf("#") > 0)
queryStringValue = queryStringValue.Substring(0, queryStringValue.IndexOf("#"));

returnValue = Convert.ToInt32(queryStringValue);
}
catch {}

return returnValue;

}

public static void RedirectToMessage (HttpContext context, ForumException exception) {

if ((exception.InnerException != null) && ( exception.InnerException is ForumException)) {
ForumException inner = (ForumException) exception.InnerException;
}
context.Response.Redirect(Globals.GetSiteUrls().Message( exception.ExceptionType ), true);
}

// *********************************************************************
// GetForumFromForumLookupTable
//
/// <summary>
/// Attempts to use forum lookup table. Capable of flushing lookup table
/// </summary>
// ***********************************************************************/
public Forum GetForumFromForumLookupTable(int forumID) {
Forum f = (Forum) this.ForumLookupTable[forumID];

if (f != null)
return f;

// Null out the cached list and attempt to reload
//
if ( (f == null) && (context.Cache["ForumsTable"] != null) )
context.Cache.Remove("ForumsTable");

f = (Forum) ForumLookupTable[forumID];

if (f == null) {
throw new Exception("Forum ID is invalid");
}

return f;
}

public Hashtable ForumLookupTable {

get {

if (HttpRuntime.Cache["ForumsTable"] == null)
HttpRuntime.Cache.Insert("ForumsTable", Forums.GetForums(this, 0, true, false), null, DateTime.Now.AddMinutes(120), TimeSpan.Zero);

return (Hashtable) HttpRuntime.Cache["ForumsTable"];
}

}

public static string GetApplicationName () {
return GetApplicationName (HttpContext.Current);
}

public static string GetApplicationName (HttpContext context) {
if (context == null)
return "";

string hostName = context.Request.Url.Host;
string applicationPath = context.Request.ApplicationPath;

return hostName + applicationPath;
}

public HttpContext Context {
get {
if (context == null)
return new HttpContext(null);

return context;
}
}

public int MessageID { get { return messageID; } }
public int ForumID { get { return forumID; } }
public int ForumGroupID { get { return forumGroupID; } }
public int PostID { get { return postID; } }
public int ThreadID { get { return threadID; } }
public int UserID { get { return userID; } }
public string UserName { get { return userName; } set { userName = value; } }
public int RoleID { get { return roleID; } }
public string QueryText { get { return queryText; } }
public string ReturnUrl { get { return returnUrl; } }
public int PageIndex { get { return (pageIndex - 1); } }
public DateTime RequestStartTime { get { return requestStartTime; } }
public User User { get { return Users.GetUser(); } }
public string CheckGuid { get { return checkGuid; } }
public SiteStatistics Statistics { get { return SiteStatistics.LoadSiteStatistics(context, true, 3); }}
public bool IsElite{get{return this.isElite;}} //fzuray 精华
public bool IsSubject{get{return this.isSubject;}} //fzuray 专题
}
}