|ClickOnce Deployment in .NET Framework 2.0
By Thiru Thangarathinam
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It is very common among the developers of previous generations to choose web applications over rich Windows UIs because of the deployment challenges associated with deploying a Smart Client Windows Forms application. However with the release of Visual Studio 2005, Microsoft has released a new technology named ClickOnce that is designed to solve the deployment issues for a windows forms application. This new technology not only provides an easy application installation mechanism but also enables easy deployment of upgrades to existing applications. This article will demonstrate how to take advantage of the excellent features of the ClickOnce deployment technology by discussing examples on how to utilize this new feature.
Since the introduction of the powerful server side web technologies such as ASP, JSP, ASP.NET, developers have shown more interest in building web applications rather than in windows applications. The factors that attracted the developers toward web applications can be summarized as follows:
If you talk to the developers, you will find that the main reason for preference for web applications over windows applications is the second point in the above list. Even though this is true with traditional applications, Microsoft is making every attempt to ensuring that windows applications can be deployed and updated with the same ease as the web applications. You can see proofs of this in the initial release of .NET Framework when Microsoft introduced the deployment of windows forms application through HTTP. Using this approach, you could simply use HREF HTML element to point to a managed executable (.exe). Then when you click on the HREF link, Internet Explorer can automatically download and install the executable on the client machine. Even though this approach sounds very promising, it also presents some interesting challenges. One of the most important challenges is the downloading of the updated code through the HTTP. Since this process was not transacted, it was possible for the application to be left in an inconsistent state. Moreover there was no way for you to specify if the application could work in offline mode apart from the traditional online mode. Combined with the operational mode issue, this approach also did not provide the ability to create shortcuts that can be used to launch the application. Even though this approach presented itself with a lot of issues, it could still be used in controlled environments. However for complex multi-assembly dependant windows forms applications, you needed a transacted and easily updateable way of deployment. This is exactly what the ClickOnce technology introduced with .NET Framework 2.0 provides. In this article, we will see how to effectively use this technology to deploy a windows form application.
How does ClickOnce Deployment Technology Work?
Before we look at an example, let us understand how this technology works.
Let us look at an example to understand this.
A Simple ClickOnce Deployment Example
Let us start by creating a simple Visual C# Windows forms application named ClickOnceDemo using Visual Studio 2005. Once the project is created, place a command button on the form and double click on the command button and modify its code to look like the following.
private void btnClick_Click(object sender, EventArgs e)
If you run the ClickOnceDemo application and click on the button, you will see an output that is somewhat similar to the following depending on the location of your project folder.
Now that we have created the application, let us publish it. But before we do that, let us look at some of the properties associated with publishing of the forms application. Right click on the
At the top of the properties page is the
Using the Publish properties dialog box, you can also specify if the application is available only in online mode or in both online and offline modes. This option is available in the
By default, the .NET Framework 2.0 option will be checked and you can choose any of the remaining options depending on your application requirements.
Right below the Prerequisities option, there is a command button named
As you can see from the above dialog box, you have a number of options that allow you to exercise finer level of control over the application updates.
Right below the Updates button is the
Using the Publish options, you can not only indicate the language in which the application will be published but also specify the Start menu shortcut name. Once you publish this application to the target location, the root directory of the application install will contain a file called publish.htm, which you can use to launch the application on the client machine. By default, the name of the file is set to publish.htm and can be modified using the above dialog box.
Now that we have a understanding of the properties in a general sense, let us see how to publish the application.
Publishing the Application
To publish the application, start by selecting
In the above dialog box, you can specify the location where you want to publish the application. The locations to which you can deploy the application are: File System, Local IIS, FTP Sites, and Remote Sites. For the purposes of this example, let us leave the default value of
The default value in the above screen is dependant on the value set in the Install Mode Settings panel of the Publish properties dialog box. Then click
If you hit
The ClickOnceDemo_126.96.36.199 folder is the one that contains the .exe file and the corresponding manifest files. Since we mentioned that the prerequisites (specified through the Publish properties dialog box in the earlier section) for this application is .NET Framework 2.0, Visual Studio automatically created a folder named dotnetfx that contained the executable for installing the .NET Framework 2.0. Now that we have had a look at the files created by the wizard, let us turn our focus to the publish.htm that provides a means for launching the application.
As you can see from the above screenshot, this html page enables you to install the ClickOnceDemo application through a hyperlink. Click the
Once the application is installed, it will automatically execute the application and bring up the form. Click on the command and you will see an output that is somewhat similar to the following.
As you can see, now the path displayed the message box is different than the previously generated message box. This is because of the fact that the application is now downloaded and locally cached in the folder shown in the above message box. If you navigate to that folder from windows explorer, you will see folders as listed in the following screenshot. These folders contain files such as manifests, and the actual executable itself and so on.
You will also notice the following changes as a result of the installation.
From this point onwards, you can launch the application through the shortcut in the
The features of ClickOnce we have seen in this article are only the tip of the iceberg and it offers many more benefits. However, the key motivation for using ClickOnce is the ease of deployment, installation, and versioning for your Windows Forms applications.