.net 在实施microsoft.build.utilities.task时，如何访问构建的各种环境变量？

在实施microsoft.build.utilities.task时，如何访问构建的各种环境变量

例如“TargetPath”

我知道我可以将它作为任务XML的一部分传入

<MyTask TargetPath="$(TargetPath)" />

但是如果我可以访问代码中的变量，我不想强迫任务的使用者必须这样做

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你不可能轻易做到这一点，你不应该这么做。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

免责声明：不要这样做！ 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;
}

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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);

string targetPath=buildEngine.GetEnvironmentVariable（“targetPath”，true）.First（）；
字符串intermediateAssembly=buildEngine.GetEnvironmentVariable（“intermediateAssembly”，true）.First（）；
IEnumerable ReferencePath=buildEngine.GetEnvironmentVariable（“ReferencePath”，true）；

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是的，这是一个丑陋的黑魔法，但它是有效的。

我的情况是，当从msbuild调用SQLCMD脚本时，我需要为它构建一个参数列表；我们不希望每次SQL脚本作者需要传入新属性时都必须重新编写MsBuild任务。这很好地解决了这个问题。