实现microsoft.build.utilities.task时,如何访问生成的各种环境变量?

我想出了办法

public static class BuildEngineExtensions
{
    const BindingFlags bindingFlags = BindingFlags.NonPublic | BindingFlags.FlattenHierarchy | BindingFlags.Instance | BindingFlags.Public;

    public static IEnumerable GetEnvironmentVariable(this IBuildEngine buildEngine, string key,bool throwIfNotFound)
    {
        var projectInstance = GetProjectInstance(buildEngine);

        var items = projectInstance.Items
            .Where(x => string.Equals(x.ItemType, key, StringComparison.InvariantCultureIgnoreCase)).ToList();
        if (items.Count > 0)
        {
            return items.Select(x => x.EvaluatedInclude);
        }


        var properties = projectInstance.Properties
            .Where(x => string.Equals(x.Name, key, StringComparison.InvariantCultureIgnoreCase)).ToList();
        if (properties.Count > 0)
        {
            return properties.Select(x => x.EvaluatedValue);
        }

        if (throwIfNotFound)
        {
            throw new Exception(string.Format("Could not extract from '{0}' environmental variables.", key));
        }

        return Enumerable.Empty();
    }

    static ProjectInstance GetProjectInstance(IBuildEngine buildEngine)
    {
        var buildEngineType = buildEngine.GetType();
        var targetBuilderCallbackField = buildEngineType.GetField("targetBuilderCallback", bindingFlags);
        if (targetBuilderCallbackField == null)
        {
            throw new Exception("Could not extract targetBuilderCallback from " + buildEngineType.FullName);
        }
        var targetBuilderCallback = targetBuilderCallbackField.GetValue(buildEngine);
        var targetCallbackType = targetBuilderCallback.GetType();
        var projectInstanceField = targetCallbackType.GetField("projectInstance", bindingFlags);
        if (projectInstanceField == null)
        {
            throw new Exception("Could not extract projectInstance from " + targetCallbackType.FullName);
        }
        return (ProjectInstance)projectInstanceField.GetValue(targetBuilderCallback);
    }
}

它可以这样使用

string targetPath = buildEngine.GetEnvironmentVariable("TargetPath", true).First();
string intermediateAssembly = buildEngine.GetEnvironmentVariable("IntermediateAssembly", true).First();
IEnumerable<string> referencePaths = buildEngine.GetEnvironmentVariable("ReferencePath", true);

是的,这是丑陋和黑魔法,但它的工作。

你不可能轻易做到这一点,你也不应该这么做。任务不应该知道它的执行上下文,而应该使用它的输入参数。

如果你真的想这样做,你需要用类似的东西重新分析项目文件。

public override bool Execute()
{
  string projectFile = BuildEngine.ProjectFileOfTaskNode;

  Engine buildEngine = new Engine(System.Runtime.InteropServices.RuntimeEnvironment.GetRuntimeDirectory());

  Project project = new Project(buildEngine);
  project.Load(projectFile);
  foreach(var o in project.EvaluatedProperties)
  {
    // Use properties
  }

  // Do what you want

  return true;
}