If you want to install two different versions on the same machine, you need to do three things before you publish your ClickOnce packages:
- Each version needs it's own "Assembly Name" on the properties page
Right Click Project -> Select "Properties" -> Select "Application" tab -> Change "Assembly name" to something like "[YourCurrentAssemblyName].Dev"
- Each version will need to have it's own "Product Name" in the publish properties
Right Click Project -> Select "Properties" -> Select "Publish" tab -> Select "Options" -> In the "Description" section, change the "Product name" to something like "[YourCurrentApplicationName] Dev"
- Each version will need a unique assembly guid in the applications assembly.cs file
Expand your project "Properties" in the solution explorer and open up your "Assembly.cs" file. Find the following line:
[assembly: Guid("D3461344-B663-4698-B32B-F52041D7B093")]
Change the guid there to something different, which you must remember for each environment. So every time you build for dev it should use the same guid it used before, but the guid should be different for each environment.
You should be able to build your project and publish it for different environments if you follow these steps.