怎么在textbox7插入数据库前判断已存在并弹出提示框

Question

怎么在textbox7插入数据库前判断已存在并弹出提示框，就像下面已经写好的”用户名已存在那样“
namespace InternetShopping.AdminManage
{ 
    public partial class UserRegister : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string num = ("Server=(local);Integrated Security=SSPI;database=bookshopping");
            SqlConnection connect = new SqlConnection(num);
            string sql = "select count(*) from Custom";
            SqlCommand command = new SqlCommand(sql, connect);
            connect.Open();
            int numcount = Convert.ToInt32(command.ExecuteScalar());
            numcount++;
         TextBox7.Text=numcount.ToString ();
        
        }
        protected void Button1_Click1(object sender, EventArgs e)
        {
            string UserName = this.TextBox1.Text;
            TextBox1.Text = "";
            string num = ("Server=(local);Integrated Security=SSPI;database=bookshopping");
            SqlConnection connect = new SqlConnection(num);
            string sql = "select *from Custom where customName='" + UserName + "'";
            SqlCommand command = new SqlCommand(sql, connect);
            
            connect.Open();
            int num1 = Convert.ToInt32(command.ExecuteScalar());
            if (num1 > 0 )
            {
                Response.Write("<script>alert('用户名已存在');</script>");
            }
            else
            {
                SqlDataSource1.Insert();
                Response.Redirect("BuyComputerBooks.aspx");
            }
            connect.Close();}}
}

Answer 1

ASHX + AJAX 吧

Answer 2

namespace InternetShopping.AdminManage
{ 
    public partial class UserRegister : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
           string txtName=TextBox7.Text;
            string num = ("Server=(local);Integrated Security=SSPI;database=bookshopping");
            SqlConnection connect = new SqlConnection(num);
            string sql = "select txtName from Custom where txtName="txtName";
            SqlCommand command = new SqlCommand(sql, connect);
            connect.Open();
            int numcount = Convert.ToInt32(command.ExecuteScalar());
           if (numcount.length>0 )
            {
                Response.Write("<script>alert('用户名已存在');</script>");
            }
        
        }
       

Answer 3

做一个光标离开事件,然后在事件中查询数据库,这是简单的,无刷新就得用ajax

Answer 4

控件有个属性,mouseleave,应该是这样拼,光标重控件中离开触发的事件,你把验证写在这个里面

Answer 5

protected void Button1_Click1(object sender, EventArgs e)
{
            string UserName = this.TextBox1.Text;
            TextBox1.Text = "";
            string num = ("Server=(local);Integrated Security=SSPI;database=bookshopping");
            SqlConnection connect = new SqlConnection(num);
            string sql = "select *from Custom where customName='" + UserName + "'";
            SqlCommand command = new SqlCommand(sql, connect);
            
            connect.Open();
            int num1 = Convert.ToInt32(command.ExecuteScalar());
            if (num1 > 0 )
            {
                Response.Write("<script>(function(){alert('用户名已存在');})()</script>");
            }
            else
            {
                SqlDataSource1.Insert();
                Response.Redirect("BuyComputerBooks.aspx");
            }
            connect.Close();}

Answer 6

这个事件坑爹的。。如果你的光标就没有上去过  这个事件是不会触发的  最妥的办法就是 Ajax  或者直接后台保存之前校验。