宿主环境内有这样一个数据，如下：

public class MyObject
    {
        public int MyValue { get; set; }
        public string MyString { get; set; }
    }

在Activity内访问该对象实例的方法如下：

public sealed class SymbolUser : CodeActivity
    {
        protected override void Execute(CodeActivityContext context)
        {
            SymbolResolver symbolResolver = context.GetExtension<SymbolResolver>();
            MyObject obj = symbolResolver["CustomObject"] as MyObject;
            Console.WriteLine(obj.MyString);
        }

    }

宿主的代码如下：

class Program
    {
        static void Main(string[] args)
        {
            WorkflowApplication WFApp = new WorkflowApplication(new Workflow1());
            SymbolResolver symbolResolver = new SymbolResolver();
            WFApp.Extensions.Add(symbolResolver);
            symbolResolver.Add("CustomObject", new MyObject() { MyValue = 1, MyString = "TestString" });
            WFApp.Run();
            Console.ReadLine();

        }
    }

当SymbolUser Activity执行的时候就可以得到new MyObject()的属性信息了。