c# - HTML 未显示在直连网站中

Question

我在 C# 中使用 Microsoft Bot Framework 编写了一个机器人，并在其中包含了以下 html

        await context.PostAsync($"How would you like to connect, {username} ?");
        StringBuilder sb = new StringBuilder();
        sb.Append("<html><head>");
        sb.Append("<style>");
        sb.Append(".button{"); sb.Append("padding:10px25px;background-color:white;text-align:center;cursor:pointer;outline:none;color:#66b3ff;background-color:white;border-width:1px;border-color:#a6a6a6;border-radius:0px;}");
        sb.Append(".button:hover{"); sb.Append("border-color:#66b3ff;color:#66b3ff;background-color:white;}");
        sb.Append(".button:active{"); sb.Append("color:white;background-color:#66b3ff;border-color:#66b3ff;}");
        sb.Append("</style>");
        sb.Append("</head><body>");
        sb.Append("<a href=\"mailto:abc@abc.com?Subject=Place%20Subject%20here");
        sb.Append("\" target=\"_top\"><button class=\"button\">");
        sb.Append("Connect with Mail"); sb.Append("</button></a>");
        sb.Append("<a href=\"tel:+1111111111\"><button class=\"button\">");
        sb.Append("Connect with Call"); sb.Append("</button></a>");
        sb.Append("</body></html>");
        await context.PostAsync(sb.ToString());

在机器人模拟器中测试时，它工作正常。看起来像这样