default.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>
<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
Namespace="System.Web.UI" TagPrefix="asp" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
</div>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:TextBox ID="TextBox1" runat="server" AutoPostBack="True" OnTextChanged="TextBox1_TextChanged"></asp:TextBox>
</ContentTemplate>
</asp:UpdatePanel>
<asp:UpdateProgress ID="UpdateProgress1" runat="server">
<ProgressTemplate>
正在检测中...........
</ProgressTemplate>
</asp:UpdateProgress>
</form>
</body>
</html>
default.aspx.cs 部分内容
protected void TextBox1_TextChanged(object sender, EventArgs e)
{
if(ValidateExistUser (TextBox1 .Text.Trim ()))
{
Label1.Text = "<font color=red>用户已存在！</font>";
}
else
{
Label1.Text = "<font color=green>可以注册！</font>";
}
}
private bool ValidateExistUser(string username)
{
string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["hdbpbjConnectionString"].ConnectionString;
using (SqlConnection conn = new SqlConnection(connectionString))
{
SqlCommand cmd = conn.CreateCommand();
cmd.CommandText = "select count(0) from users where username=@name";
cmd.Parameters.AddWithValue("@name", username);
conn.Open();
return ((int)cmd.ExecuteScalar()) > 0 ? true : false;
}
}