How do I deploy two ClickOnce versions simultaneously?

I manually edited the .csproj to specify a different ProductName for debug/release.

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
    ...
    <PublishUrl>publishbeta\</PublishUrl>
    <InstallUrl>http://www.softwareabc.com/download/beta/</InstallUrl>
    <ProductName>Software ABC Test</ProductName>
    <AssemblyName>SoftABCTest</AssemblyName>
    <ApplicationIcon>Resources\Test.ico</ApplicationIcon>
  </PropertyGroup>
  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
    ...
    <PublishUrl>publish\</PublishUrl>
    <InstallUrl>http://www.softwareabc.com/download/</InstallUrl>
    <ProductName>Software ABC</ProductName>
    <AssemblyName>SoftABC</AssemblyName>
    <ApplicationIcon>Resources\Application.ico</ApplicationIcon>
</PropertyGroup>

One caveat is that Visual Studio 2010 doesn't update this if you switch between debug/release. It only takes effect when it loads the solution so make sure to switch debug/release then close and reopen the solution.

ClickOnce: Concurrent versions explains how to do this.

It might sound kind of lame, but the easiest way to do this is to have two EXE projects in your solution. The Main method of each of these will just call the Main method in your original EXE project (which you'll have just switched over to being a DLL file).

This means that each EXE project can have its own ClickOnce publishing settings, as well as its own app.config file. This means you have different connection strings for the production and the test version.

Your other option (the one that might seem to make the most sense) is to use MageUI.exe to manually build the ClickOnce files, which would let you choose a different configuration file and publish location each time you ran the tool. There's also a command line version (Mage.exe) so you could in theory automate this.

However, we found that the solution with two "runner" projects was far far simpler. I'd recommend you try that first.