CodeSmith Generator 6: Task-based Asynchronous Pattern

Overview

In CodeSmith Generator 6 we are upgrading the codebase to use .NET 4.0 framework. Using the.NET 4.0 framework gives us access the Task Parallel Library (TPL).  We plan to make heave use of the Task-based Asynchronous Pattern (TAP) to provide asynchronous call support to our API for generating templates. Microsoft describes the pattern as follows. “The Task-based Asynchronous Pattern (TAP) is a new pattern for asynchrony in the .NET Framework.  It is based on the Task and Task<TResult> types in the System.Threading.Tasks namespace, which are used to represent arbitrary asynchronous operations.” Much greater support will be added for this pattern in future version of the .NET framework, see Microsoft Visual Studio Async CTP.  However, there is no reason we can’t make use of the pattern today. 

Sample

First, a big warning that this syntax is subject to change as we evolve the code.  Here is an example of how you can use TAP and Generator API to compile and generate a template.

Task<CompileTemplateResult> task = TemplateEngine.CompileFileAsync(path);
task.ContinueWith(t =>
    {
        if (t.IsFaulted)
            return LogError(t.Exception);
        if (t.IsCanceled)
            return LogCanceled();

        CompileTemplateResult result = t.Result;
        CodeTemplate template = result.CreateTemplateInstance();

        return template.RenderToString();
    })
    .ContinueWith(r =>
    {
        if (r.IsCompleted)
            SaveOutput(r.Result);
    });