This article was originally published in the May 2001 issue of the InstallShield Newsletter
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Abstract: Often applications require that a certain version of Microsoft Internet Explorer or some other third party software be installed on the target system. For instance, HTML Help requires Internet Explorer 3.0. This article explains how to search for Internet Explorer 5.5 or above and abort setup with an error message if it is not found. The same technique can be used to search for other applications.
To find out which version of Internet Explorer is installed, we'll examine the file version of Shdocvw.dll. In knowledge base article Q164539 Microsoft has documented that the existance of this file indicates that IE is installed, and how its file version relates to the installed IE version. Shdocvw.dll can be found in the system folder, as stored in Windows Installer's built in property [SystemFolder]. On Windows NT and 2000 this property typically resolves to C:\Winnt\System32 and on Windows 95, 98 and Me to C:\Windows\System. The following table shows some selected entries for IE versions. For a complete list see the knowledge base article.
|Shdocvw.dll File Version||Internet Explorer Version|
|4.70.1155||Internet Explorer 3.0|
|4.71.1712.5||Internet Explorer 4.0|
|4.72.3612.1707||Internet Explorer 4.01 SP2|
|5.0.2014.213||Internet Explorer 5.0|
|5.50.4134.600||Internet Explorer 5.5|
Note that Shdocvw.dll has a major version of 4 even in Internet Explorer 3.0, only the minor version number is different between IE3 and IE4.
Windows Installer has some standard actions and tables that we can use to search for Shdocvw.dll and examine its version number. However in this case InstallShield has not provided a wizard or any other abstraction layer to populate these tables, so we have to use the Power Editor that can be found under Advanced Views in IPWI 2.0. It is also available from the menu bar: pull down the Project menu in IPWI 2 or the Tools menu in ISWI 1.x and select Power Editor.
The first table we'll populate is the AppSearch table. It requires two entries: a property and a signature. Windows Installer will set the property to the full path of Shdocvw.dll if a sufficient version is found. It has to be a public property, i.e. its name can only consist of upper case letters and numbers, no lower case letters are allowed. We don't have to add this property in the Property Manager. The signature is used to reference the other table entries we'll make to specify our search. Enter the following information in the AppSearch table:
Now we need to tell Windows Installer which file we are looking for, and what version we require. This is done by populating the Signature table as shown below. Since this is a table with many columns I've broken it into two lines for better readability.
Signature is the same as above and used to connect the row in the Signature table to the corresponding row in the AppSearch table. The entry for FileName should be obvious. MinVersion specifies the minimal version of the file that must exist to meet our requirements (see below). We leave the other fields empty to indicate that we don't care about the file size, date or language of Shdocvw.dll.
The MinVersion field is exclusive, i.e. the actual file version must be greater (>) than the version number we enter here, not "greater than or equal" (>=). Therefore we must enter a version number that is actually 1 less than the version we are looking for. We are looking for 5.50.4134.600, so we enter 5.50.4134.599.
If you wanted to specify a file date you'd have to use the MS-DOS format in the MinDate and MaxDate columns, i.e. some arithmetic is required:
( (Year - 1980) * 512 + Month * 32 + Day ) * 65535 + Hours * 2048 + Minutes * 32 + Seconds/2
Finally we must tell Windows Installer where to search for the file. We know that Shdocvw.dll will always reside in the system directory, so we fill in the DrLocator table as follows.
The signature is again the same as above, to associate the rows is the three tables with each other. We leave the Parent field empty because we specify the full path in the Path column. We use the built in property [SystemFolder] which will automatically resolve to the correct path of the system folder on the target machine. We set the search Depth to 0 because we know that Shodvw.dll is in the system folder, not a subdirectory thereof.
If you don't know where the file will be located on the user's hard disk, you can leave both fields, Parent and Path, empty. In this case Windows Installer will search all fixed drives for the file, scanning as many subdirectory levels as specified in the Depth column (0 will only scan the root directory). Note that this can take a long time, depending on the number and size of local drives/partitions and the specified search depth.
Now that we have a property that will only be set if Internet Explorer 5.5 is installed, we need to set up an error message that will abort the installation if the property is empty. This can be done with a custom action of type 19 "Display error message and terminate the installation". This type of custom action is not available in InstallShield's custom action wizard.
Right click the custom actions view and select "New" to create a new custom action. Name the action "IE55Error". Fill in the proprty sheet as shown in the following table:
|Target||This application requires Microsoft Internet Explorer 5.5 or above|
|Comments||Terminate setup if IE 5.5 isn't installed|
Instead of storing the text for the error message directly in the target field, we could have added an entry to the error table, which has advantages for multi-language setups. For simplicity I haven't used this method here.
Insert the IE55Error custom action in the Installation User Interface sequence after the AppSearch standard action and give it the following condition:
Not IE55FOUND And Not Installed
This will terminate setup with a message box like below if the specified minimum version of Shdocvw.dll isn't found. We want to do this only on first time install, else we would prevent uninstallation if the user deletes Shdocvw.dll after installing our application.
We also need to insert the IE55Error custom action in the Installation Execute sequence (with the same condition), because in a silent install the User Interface sequence is not processed.
Finally make sure that the AppSearch standard action has no condition attached in either sequence. Early versions of ISWI used to put a condition of APPS_TEST on the AppSearch action, so that it wouldn't execute.
Stefan Krueger is working as freelance setup consultant, offering support, custom programming and workshops independently from InstallShield Software Corporation. Besides his contract work, he answers questions in various newsgroups and maintains the InstallSite.org web site, a place where setup developers share resources and information among peers.
If you have any comments about this article, or want to suggest a topic that Stefan should discuss in a future article, please write to . To read Stefan's articles from previous issues of the InstallShield Newsletter, please visit http://www.installsite.org/isnews.htm.
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