Request.Headers

This provides useful information. With the data in this collection, we can decide how to render a response. And we can generate statistics about the visitors of a website.

Benefits

You can benefit from analyzing HTTP headers used with your site. The code will also let you see what cookies are being sent to your application.

Example

This code example shows how to access the collection of HTTP headers in ASP.NET. It uses Page_Load and the NameValueCollection.

using System;
using System.Web.UI;
using System.Collections.Specialized;

public partial class _Default : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        NameValueCollection headers = base.Request.Headers;
        for (int i = 0; i < headers.Count; i++)
        {
            string key = headers.GetKey(i);
            string value = headers.Get(i);
            base.Response.Write(key + " = " + value + "<br/>");
        }
    }
}

Record values

You can add a C# code file to the App_Code folder in your ASP.NET project. This code will record each individual value for each key in the Headers collection.

using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Web;

public static class HeaderStatTool
{
    static List<HeaderData> _list = new List<HeaderData>();

    class HeaderData
    {
        public string Key { get; set; }
        public int Index { get; set; }
        public string Value { get; set; }
    };

    public static void Record(HttpRequest q)
    {
        try
        {
            NameValueCollection headers = q.Headers;
            if (headers != null)
            {
                for (int i = 0; i < headers.Count; i++)
                {
                    _list.Add(new HeaderData()
                    {
                        Key = headers.GetKey(i),
                        Index = i,
                        Value = headers.Get(i)
                    });
                }
            }
        }
        catch
        {
        }
    }
}

Diagnostics

This property uses some logic with List and Dictionary to report the important parts of the HTTP headers sent to your application. It should be a method, not a property.

public static string Diagnostics
{
    get
    {
        // 1: Store results in StringBuilder
        StringBuilder builder = new StringBuilder();
        try
        {
            // 2: Get all names of headers
            var nameDictionary = new Dictionary<string, bool>();
            foreach (HeaderData data in _list)
            {
                if (!nameDictionary.ContainsKey(data.Key))
                {
                    nameDictionary.Add(data.Key, true);
                }
            }
            // 3: Loop through names
            foreach (string name in nameDictionary.Keys)
            {
                try
                {
                    // 4: Write name and count of the name
                    var nameList = _list.FindAll(item => item.Key == name);
                    builder.AppendFormat("Header: {0} = {1} items\n",
                        name,
                        nameList.Count);

                    // 5: Count index frequencies
                    for (int i = 0; i < 10; i++)
                    {
                        int count = nameList.FindAll(item => item.Index == i).Count;
                        if (count != 0)
                        {
                            builder.AppendFormat("  Index: {0} = {1} items\n",
                                i,
                                count);
                        }
                    }
                    // 6: Get frequencies of values
                    var valueDictionary = new Dictionary<string, int>();
                    foreach (HeaderData data in nameList)
                    {
                        if (valueDictionary.ContainsKey(data.Value))
                        {
                            valueDictionary[data.Value]++;
                        }
                        else
                        {
                            valueDictionary.Add(data.Value, 1);
                        }
                    }
                    // 7: Write values and frequencies
                    foreach (var keyValuePair in valueDictionary)
                    {
                        builder.AppendFormat("  Value: {0} = {1} count\n",
                            keyValuePair.Key,
                            keyValuePair.Value);
                    }
                }
                catch
                {
                    builder.AppendFormat("Error: {0}\n", name);
                }
            }
        }
        catch
        {
            builder.Append("Error\n");
        }
        // 8: Return the result string
        return builder.ToString();
    }
}
Header: Host = 1730 items
  Index: 0 = 4 items
  Index: 1 = 25 items
  Index: 2 = 42 items
  Index: 3 = 44 items
  Index: 4 = 642 items
  Index: 5 = 375 items
  Index: 6 = 496 items
  Index: 7 = 94 items
  Index: 8 = 3 items
  Index: 9 = 5 items
  Value: dotnetperls.com = 1714 count
  Value: www.dotnetperls.com = 16 count

Header: Accept-Encoding = 740 items
  Index: 1 = 11 items
  Index: 2 = 265 items
  Index: 3 = 175 items
  Index: 4 = 276 items
  Index: 5 = 12 items
  Index: 6 = 1 items
  Value: gzip, deflate = 282 count
  Value: gzip,deflate,bzip2,sdch = 95 count
  Value: gzip,deflate = 227 count
  Value: deflate, gzip, x-gzip, identity, *;q=0 = 10 count
  Value: gzip, x-gzip = 10 count
  Value: gzip = 106 count
  Value: identity = 3 count
  Value: gzip, deflate, identity = 6 count
  Value: gzip,identity = 1 count

Summary

We developed code to add live reporting of the kinds of HTTP requests that are accessing an ASP.NET server. This helps with debugging and can improve a website.