从CRM Workflow上下文中检索ITokenService

Question

目前我正在开展CRM项目。在这个项目中，我必须将数据发送到Web服务。此操作必须适用于自定义工作流程。为了进行Web服务调用我需要身份验证令牌，目前我正在尝试从CodeActivityContext获取ITokenService，它正在检索null，有关如何在工作流环境中获取ITokenService的任何建议吗？

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protected override void Execute(CodeActivityContext executionContext)
{
    IWorkflowContext context = executionContext.GetExtension<IWorkflowContext>();
    IOrganizationServiceFactory serviceFactory = executionContext.GetExtension<IOrganizationServiceFactory>();
    ITracingService tracingService = executionContext.GetExtension<ITracingService>();
    ITokenService TokenService = (ITokenService)executionContext.GetExtension<ITokenService>();
    if(TokenService == null) throw new InvalidOperationException("Token service is null");
    serviceFactory.CreateOrganizationService(context.UserId)

    try
    {
        //do something
    }
    catch
    {
        //do something
    }
}