Recipe 18.4 Determining the User 's Browser Type 18.4.1 Problem Your application requires the use of a specific browser and you want to determine whether the required browser is being used before allowing a user to access your application. 18.4.2 Solution Use the properties of the Request.Browser object to determine the browser type and version, and then take the action required by your application. In the code-behind class for the page, use the .NET language of your choice to: -
Use the Browser property of the Request.Browser object to return a string representing the full browser type, such as "IE" in the case of Internet Explorer. -
Use the Version property of the Request.Browser object to return a string that represents the major and minor version of the browser, such as "6.0" in the case of IE 6.0. -
Take action accordingly , such as outputting a message indicating whether the user's browser is compatible with the application. Example 18-10 through Example 18-12 show the .aspx file and the VB and C# code-behind files for an application that demonstrates the solution. The output of our example program is shown in Figure 18-2. Figure 18-2. Determining the user's browser 
18.4.3 Discussion With the variety of different browsers in use today and the significant variation in their capabilities, it is not uncommon to need to determine the type of browser being used. Then, based on the browser, you may need to inform the user that the browser is incompatible with your application or output different HTML to support the specific browser. Our example demonstrates the functionality provided in ASP.NET to determine the browser type and version, and then output this information along with a message indicating whether the user's browser is compatible with the application. The .aspx file contains two asp:Literal controls used to output messages to the user. The first outputs the browser version information, and the second informs the user whether his browser is compatible with the application. In the Page_Load method of the code-behind, the Browser and Version properties of the Request.Browser object are used to create a message to inform the user of the detected browser version. The Browser property returns a string such as "IE", "Netscape", "Opera", etc. The Version property returns a string that represents the major and minor version of the browser. For Internet Explorer 6.0, for instance, the Browser property will return "IE" and the Version property will return "6.0". Next, the browser type and major version number are compared to the minimum requirements for the application (IE and Version 5). If the browser is IE 5.0 or later, a message is displayed indicating the browser is compatible with the application. Otherwise, a message is displayed indicating the application requires IE 5.0 or later. For your application, you might want to check the browser version on the home page. If the browser is compatible with your application, output the home page normally. Otherwise, redirect the user to a message page indicating the browser requirements. The Request.Browser object contains many properties not used in this example but that may be useful in your application. Table 18-1 lists some of the commonly used properties. For a complete list of the available properties, refer to the documentation on the HttpBrowserCapabilities class in the MSDN Library. Table 18-1. Commonly used browser object properties | Property | Description | | Browser | Returns a string indicating the browser type (IE, Netscape, Opera, etc.) | | Cookies | Returns a Boolean value indicating whether the browser supports cookies | | JavaScript | Returns a Boolean value indicating whether the browser supports JavaScript | | MajorVersion | Returns an integer value indicating the major version of the browser (integer portion of the browser version) | | MinorVersion | Returns an double value indicating the minor version of the browser (decimal portion of the browser version) | | Version | Returns a string representing the full browser version (integer and decimal portion) |
 | Properties that return Boolean values, such as Cookies and JavaScript , indicate what the browser is capable of supporting but not necessarily the current configuration. If the browser supports cookies but the user has configured the browser to disable cookies, the Cookies property will still return true. | |
18.4.4 See Also HttpBrowserCapabilities documentation in the MSDN Library Example 18-10. Determining the user browser type (.aspx) <%@ Page Language="vb" AutoEventWireup="false" Codebehind="CH18DeterminingBrowserVB.aspx.vb" Inherits="ASPNetCookbook.VBExamples.CH18DeterminingBrowserVB" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>Determining Browser</title> <link rel="stylesheet" href="css/ASPNetCookbook.css"> </head> <body leftmargin="0" marginheight="0" marginwidth="0" topmargin="0"> <form id="frmDetermineBrowser" method="post" runat="server" > <table width="100%" cellpadding="0" cellspacing="0" border="0"> <tr> <td align="center"> <img src="images/ASPNETCookbookHeading_blue.gif"> </td> </tr> <tr> <td class="dividerLine"> <img src="images/spacer.gif" height="6" border="0"></td> </tr> </table> <table width="90%" align="center" border="0"> <tr> <td><img src="images/spacer.gif" height="10" border="0"></td> </tr> <tr> <td align="center" class="PageHeading"> Determining User Browser (VB) </td> </tr> <tr> <td><img src="images/spacer.gif" height="10" border="0"></td> </tr> <tr> <td align="center" class="MenuItem"> <asp:Literal ID="litBrowser" Runat="server" /> <br /><br /> <asp:Literal ID="litMessage" Runat="server" /> </td> </tr> </table> </form> </body> </html>
Example 18-11. Determining the user browser type code-behind (.vb) Option Explicit On Option Strict On '----------------------------------------------------------------------------- ' ' Module Name: CH18DeterminingBrowserVB.aspx.vb ' ' Description: This module provides the code behind for the ' CH18DeterminingBrowserVB.aspx page ' '***************************************************************************** Namespace ASPNetCookbook.VBExamples Public Class CH18DeterminingBrowserVB Inherits System.Web.UI.Page 'controls on the form Protected litBrowser As System.Web.UI.WebControls.Literal Protected litMessage As System.Web.UI.WebControls.Literal '************************************************************************* ' ' ROUTINE: Page_Load ' ' DESCRIPTION: This routine provides the event handler for the page load ' event. It is responsible for initializing the controls ' on the page. '------------------------------------------------------------------------- Private Sub Page_Load(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles MyBase.Load 'output user browser litBrowser.Text = "Your browser is " & _ Request.Browser.Browser & " " & _ Request.Browser.Version 'check to see if it is an acceptable version If ((Request.Browser.Browser = "IE") AndAlso _ (Request.Browser.MajorVersion >= 5)) Then 'output message indicating it is OK litMessage.Text = "It is compatible with this application." Else 'output message indicating IE 5 or later must be used litMessage.Text = "This application requires IE 5.0 or later." End If End Sub 'Page_Load End Class 'CH18DeterminingBrowserVB End Namespace
Example 18-12. Determining the user browser type code-behind (.cs) //---------------------------------------------------------------------------- // // Module Name: CH18DeterminingBrowserCS.aspx.cs // // Description: This module provides the code behind for the // CH18DeterminingBrowserCS.aspx page // using System; namespace ASPNetCookbook.CSExamples { public class CH18DeterminingBrowserCS : System.Web.UI.Page { // controls on the form protected System.Web.UI.WebControls.Literal litBrowser; protected System.Web.UI.WebControls.Literal litMessage; //************************************************************************ // // ROUTINE: Page_Load // // DESCRIPTION: This routine provides the event handler for the page // load event. It is responsible for initializing the // controls on the page. //------------------------------------------------------------------------ private void Page_Load(object sender, System.EventArgs e) { // output user browser litBrowser.Text = "Your browser is " + Request.Browser.Browser + " " + Request.Browser.Version; // check to see if it is an acceptable version if ((Request.Browser.Browser == "IE") & (Request.Browser.MajorVersion >= 5)) { // output message indicating it is OK litMessage.Text = "It is compatible with this application."; } else { // output message indicating IE 5 or later must be used litMessage.Text = "This application requires IE 5.0 or later."; } } // Page_Load } // CH18DeterminingBrowserCS }
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