WiX Toolset - How to add custom action

If we want to invoke some C#(VB,C++) code in the installation package, we should add custom action.

1. Add custom action project. C# code sample:

namespace SetupAction
{
    public static class CustomActions
    {
        [CustomAction]
        public static ActionResult EnumerateSqlServers(Session session)
        {
            ...
            return ActionResult.Success;
        }

        [CustomAction]
        public static ActionResult VerifySqlConnection(Session session)
        {
            ...
            return ActionResult.Success;
        }
    }
}

1. Open the .cproj fie of custom action project, and edit it. Add code below, save and build it, will get a file named 'SetupAction.CA.dll', 'SetupAction' is the name of my custom action project. Installation will invoke the '.CA.dll'

  <Import Project="$(WixCATargetsPath)" Condition=" '$(WixCATargetsPath)' != '' " />
  <Import Project="$(MSBuildExtensionsPath32)\Microsoft\WiX\v3.x\Wix.CA.targets" 
    Condition=" '$(WixCATargetsPath)' == '' AND 
    Exists('$(MSBuildExtensionsPath32)\Microsoft\WiX\v3.x\Wix.CA.targets') " />
  <Target Name="EnsureWixToolsetInstalled" 
       Condition=" '$(WixCATargetsImported)' != 'true' ">
    <Error Text="The WiX Toolset v3.11 (or newer) build tools must be installed to 
        build this project. 
        To download the WiX Toolset, see http://wixtoolset.org/releases/" />
  </Target>

1. In the WiX project, add the custom action project to References, and define <CustomAction>

<!--The custom action DLL itself.-->
<Binary Id="WebAppCA" 
     SourceFile="$(var.SetupAction.TargetDir)$(var.SetupAction.TargetName).CA.dll" />

<!--The custom action .-->
<CustomAction Id="EnumerateSqlServers" 
                BinaryKey="WebAppCA"
		DllEntry="EnumerateSqlServers"
		Execute="immediate"
		Return="check" />

<CustomAction Id="VerifySqlConnection"
		BinaryKey="WebAppCA"
		DllEntry="VerifySqlConnection"
		Execute="immediate"
		Return="check" />

Pay attention: If the code in custom action need administrator privilege, should use another way to deal with it. Add attribute Impersonate="no" and define the parameters pass to the custom action method. Samples as below:

<CustomAction Id="SetConfigFile"
		BinaryKey="WebAppCA"
		DllEntry="SetConfigFile"
		Execute="deferred"
		Return="check" Impersonate="no"/>

<!--Define the parameters pass to CustomAction 'SetConfigFile'-->
<CustomAction Id="SetCustomActionPropertyValues"
              Property="SetConfigFile"
              Value="DATABASE_SERVER=[DATABASE_SERVER];
              DATABASE_USERNAME=[DATABASE_USERNAME];
              DATABASE_PASSWORD=[DATABASE_PASSWORD];" />

Always throw error: "Could not load file or assembly '...' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded."
Add "CustomAction.config" file to Custom Action project, and include code as below.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<startup useLegacyV2RuntimeActivationPolicy="true">
		<supportedRuntime version="v4.0"/>
	        <supportedRuntime version="v2.0.50727"/>
	</startup>
</configuration>