title: Angular: Argument of type 'number' is not assignable to parameter of type 'string'
body: <p>I am a freshman in typescript.I wrote a table but it alarmed that </p>
  
  <blockquote>
    <p>ERROR in E:/internship/angular-demo/ngdemo/src/app/_services/task.service.ts (24,27): Argument of type 'number' is not assignable to parameter of type 'string'.</p>
  </blockquote>
  
  <p>I couldn't find the answer, so I've come to ask for a way to solve it.</p>
  
  <p>Here is the code:</p>
  
  <pre><code>let params =new URLSearchParams();
  params.set('User_id',t.User_id);
  params.set('complete', t.complete);
  params.set('summary', t.summary);
  params.set('description', t.description);
  return this.http
   .post(taskUrl, params)
   .map(response =&gt; 
  response.json()); 
  </code></pre>