求个这样的正则100分上

对于正则一窍不通.
数字加字母的组合的验证.
随便数字在前面还是字母在前面都可以，就是要求数字和字母的组合.
--------------------编程问答-------------------- easy:
^(?!\d+$)(?![a-zA-Z]+$)[\da-zA-Z]+$ --------------------编程问答-------------------- <script type="text/javascript">
function checkform(obj){
  if(!checkpwd(obj.pass)){
    return false;
  };
}
function checkpwd(obj){
  if(obj.value == "")return false;
  if(obj.value.match(/[^A-Za-z0-9]/ig)){
    alert("密码只能为数字和字母");
    return false;
  }
  return true;
}
</script>
<form action="#" onsubmit="return checkform(this);">
User:<input name="user" />
Pass:<input type="password" name="pass" onblur="checkpwd(this);" />
<input type="submit" />
</form>
--------------------编程问答-------------------- [\d\w]+ --------------------编程问答-------------------- ^(?!\d+$)(?![a-zA-Z]+$)[\da-zA-Z]+$ --------------------编程问答-------------------- ^(?!\d+$)(?![a-zA-Z]+$)[\da-zA-Z]+$

补充：.NET技术 ,  ASP.NET