如何在asp.net代码隐藏中从html中选择文本？

<input type="text" id="txtContent" value="这是一个示例文本" />
<button onclick="selectText()">选择文本</button>

function selectText() {
  var textBox = document.getElementById("txtContent");
  
  if (document.body.createTextRange) { // For Internet Explorer
    var range = document.body.createTextRange();
    range.moveToElementText(textBox);
    range.select();
  } else if (window.getSelection) { // For modern browsers
    var range = document.createRange();
    range.selectNode(textBox);
    window.getSelection().removeAllRanges();
    window.getSelection().addRange(range);
  }
}

<script>
  // 将上述JavaScript代码放在这里
</script>