span 类 css 样式不适用于 aps.net 按钮

问：

下面是 Web 表单中的 css 样式代码 ASP.NET：

<style type="text/css">
  .button1c {
  background-image: linear-gradient(to right, #006175 0%, #00a950 100%);
  border-radius: 40px;
  box-sizing: border-box;
  color: #00a84f;
  display: block;
  height: 50px;
  font-size: 1.4em;
  padding: 4px;
  position: relative;
  text-decoration: none;
  width: 7em;
  z-index: 2;
}

.button1c:hover {
  color: #4c4c4c;
}

.button1c .button1span {
  align-items: left;
  background: #00a84f;
  border-radius: 40px;
  display: flex;
  justify-content: center;
  height: 50%;
  transition: background 0.5s ease;
  width: 100%;
}

.button1c:hover .button1span {
  background: transparent;
}
 
     </style>

这里尝试将 span 与 ASP.net 按钮结合起来：

  <asp:Button ID="calcID" runat="server" cssclass="button1c"  OnClick="calc_Click" Text="Solve"    />  <span class="button1span" >... </span>

我的问题是span类的css样式代码，它没有在asp按钮中仅显示cssclass