Request[]与Request.Params[] 差别

Request[]与Request.Params[] ,这二个属性都可以让我们方便地根据一个KEY去【同时搜索】QueryString、Form、Cookies 或 ServerVariables这4个集合

这二个属性唯一不同的是：Item是依次访问这4个集合，找到就返回结果，而Params是在访问时，先将4个集合的数据合并到一个新集合(集合不存在时创建)， 然后再查找指定的结果。

Request[]实现原理（.net源代码）

// System.Web.HttpRequest
/// <summary>Gets the specified object from the <see cref="P:System.Web.HttpRequest.QueryString" />, <see cref="P:System.Web.HttpRequest.Form" />, <see cref="P:System.Web.HttpRequest.Cookies" />, or <see cref="P:System.Web.HttpRequest.ServerVariables" /> collections.</summary>
/// <returns>The <see cref="P:System.Web.HttpRequest.QueryString" />, <see cref="P:System.Web.HttpRequest.Form" />, <see cref="P:System.Web.HttpRequest.Cookies" />, or <see cref="P:System.Web.HttpRequest.ServerVariables" /> collection member specified in the <paramref name="key" /> parameter. If the specified <paramref name="key" /> is not found, then null is returned.</returns>
/// <param name="key">The name of the collection member to get. </param>
public string this[string key]
{
    get
    {
        string text = this.QueryString[key];
        if (text != null)
        {
            return text;
        }
        text = this.Form[key];
        if (text != null)
        {
            return text;
        }
        HttpCookie httpCookie = this.Cookies[key];
        if (httpCookie != null)
        {
            return httpCookie.Value;
        }
        text = this.ServerVariables[key];
        if (text != null)
        {
            return text;
        }
        return null;
    }
}

Request.Params[]源码

// System.Web.HttpRequest
/// <summary>Gets a combined collection of <see cref="P:System.Web.HttpRequest.QueryString" />, <see cref="P:System.Web.HttpRequest.Form" />, <see cref="P:System.Web.HttpRequest.Cookies" />, and <see cref="P:System.Web.HttpRequest.ServerVariables" /> items.</summary>
/// <returns>A <see cref="T:System.Collections.Specialized.NameValueCollection" /> object. </returns>
public NameValueCollection Params
{
    get
    {
        if (HttpRuntime.HasAspNetHostingPermission(AspNetHostingPermissionLevel.Low))
        {
            return this.GetParams();
        }
        return this.GetParamsWithDemand();
    }
}

// System.Web.HttpRequest
private NameValueCollection GetParams()
{
    if (this._params == null)
    {
        this._params = new HttpValueCollection();
        this.FillInParamsCollection();
        this._params.MakeReadOnly();
    }
    return this._params;
}

// System.Web.HttpRequest
private void FillInParamsCollection()
{
    this._params.Add(this.QueryString);
    this._params.Add(this.Form);
    this._params.Add(this.Cookies);
    this._params.Add(this.ServerVariables);
}

参考网页http://www.cnblogs.com/fish-li/archive/2011/12/06/2278463.html