Visual Basic 2010 : Deploying Applications with ClickOnce - Registration-Free COM

7/11/2013 4:02:19 AM

One of the biggest benefits from ClickOnce is that users that do not have administrator permissions can install applications. By the way, there are situations in which an application is deployed together with some COM libraries but this can be a problem because such libraries need to be registered and a non-administrator user does not have the appropriate permissions for this. Fortunately with ClickOnce you can take advantage of a technique known as Registration-Free COM which basically makes a reference to a COM library visible to the application only, without the need of registration. You simply need to right-click the library name in Solution Explorer, References and then select Properties. Finally set the Isolated property as True (see Figure 1).

Figure 1. Isolating the library for Registration-Free COM.

When you build the project, Visual Studio also generates a manifest file that provides the actual state of isolation of the library. Listing 1 shows a sample manifest file.

Listing 1. Sample Manifest for Registration-Free COM

<?xml version="1.0" encoding="utf-8"?>
<assembly xsi:schemaLocation="urn:schemas-microsoft-com:asm.v1 assem-
bly.adaptive.xsd"
          manifestVersion="1.0" xmlns:asmv1="urn:schemas-microsoft-com:asm.v1"
          xmlns:asmv2="urn:schemas-microsoft-com:asm.v2"
          xmlns:asmv3="urn:schemas-microsoft-com:asm.v3"
          xmlns:dsig="http://www.w3.org/2000/09/xmldsig#"
          xmlns:co.v1="urn:schemas-microsoft-com:clickonce.v1"
          xmlns:co.v2="urn:schemas-microsoft-com:clickonce.v2"
          xmlns="urn:schemas-microsoft-com:asm.v1"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <assemblyIdentity name="Native.MyCOMLibrary" version="1.0.0.0" type="win32" />
  <file name="wmp.dll" asmv2:size="11406336">
    <hash xmlns="urn:schemas-microsoft-com:asm.v2">
      <dsig:Transforms>
        <dsig:Transform
         Algorithm="urn:schemas-microsoft-com:HashTransforms.Identity" />
      </dsig:Transforms>
      <dsig:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
      <dsig:DigestValue>cCyT3Cw0dm68HkliYf3ncYjoCKU=</dsig:DigestValue>
    </hash>
    <typelib tlbid="{6bf52a50-394a-11d3-b153-00c04f79faa6}"
         version="1.0" helpdir="" resourceid="0" flags="HASDISKIMAGE" />
    <comClass clsid="{6bf52a52-394a-11d3-b153-00c04f79faa6}"
              threadingModel="Apartment"
              tlbid="{6bf52a50-394a-11d3-b153-00c04f79faa6}"
              progid="WMPlayer.OCX.7"
              description="Windows Media Player ActiveX Control" />
  </file>
</assembly>

The manifest file is part of the setup process, so you need to include it in your ClickOnce deployment (Visual Studio takes care for you). If you are interested in understanding how the Registration-Free COM technique actually works, you can read a specific article in the MSDN Magazine available at this address: http://msdn.microsoft.com/en-us/magazine/cc188708.aspx.