TFS API: Accessing build definition values programmatically

I’m working on some build customization and I needed to be able to access parameter values from my build definition programmatically.  It turned out to be pretty easy once I knew where to look:

We start off by connecting to TFS and then to the Build Service:

TfsTeamProjectCollection server = new TfsTeamProjectCollection(new Uri("http://myTFS:8080/tfs"));
server.EnsureAuthenticated(); 
IBuildServer build = (IBuildServer)server.GetService(typeof(IBuildServer));

That is followed by retrieving the build definition…you have a couple of options here, as you can use the build definition URL (something like vstfs:///Build/Definition/36), or you can supply the project name and build definition name, which makes things more readable:

IBuildDefinition buildDefinition = build.GetBuildDefinition("MyProject", "MyDefinition");

Build definition has a property called ProcessParameters where you can get all the names and values of the parameters that are defined in your build definition.  Don’t confuse that with buildDefinition.Process.Parameters, as that gives you the values as found in the underlying build template.  The ProcessParameters property is a string, but it stores a serialized Dictionary with all the keys and values found in the definition.  This code helps you get the values out of it (in my case I was looking for a string array):

object argumentValue;
if (WorkflowHelpers.DeserializeProcessParameters(buildDefinition.ProcessParameters).TryGetValue("MyArgumentName", out argumentValue))
{
    return (string[])argumentValue;
}