how to validate a form by using javasrcipt and then connect it to database by asp.net

<script language="javascript" type="text/javascript">

function Validation()
{
var userid=document.getElementById('<%=txtUserID.ClientID %>');
var pwd=document.getElementById('<%=txtPwd.ClientID %>');
if(userid.value=="")
{
alert("Please Enter UserID");
userid.focus();
return false;
}
if(pwd.value=="")
{
alert("Please Enter Password");
pwd.focus();
return false;
}
}
    </script>

protected void btnLogin_Click(object sender, EventArgs e)
    {

            string query = "SELECT USerID,Password WHERE UserID='" + txtUserID.Text + "' AND Password='" + txtPwd.Text + "' AND Active='True'";
            SqlDataAdapter da=new SqlDataAdapter(query,connectionstring);
            connectionstring.Open();
            DataSet ds = new DataSet();
            da.Fill(ds);
             connectionstring.Close();
            
            ds.Tables[0].TableName = "LoginDetails";
            if (ds.Tables["LoginDetails"].Rows.Count > 0)
            {
            }
            else
            {
             lblError.Text = "UserID or Password are Incorrect";
            }
}