asp.net注册页面如何验证用户名是否在数据库存在？求代码

你是想直接在页面就查询数据库？？

建议你不要这么做

ajax的话

                 var userName = $('#txtName').val();
                var userPassword = $('#txtPwd').val();
                var rememberMe = document.getElementById("rememberMe").checked;
                $.ajax({
                    type: "POST",
                    contentType: "application/json;charset=utf-8",
                    url: "数据提交的url",
                    data: "{username:'" + userName + "',password:'" + userPassword + "',strIsLongLogin:'" + rememberMe + "'}",
                    dataType: 'json',
                    success: function (result) {
                    if(result.d=="存在"){alert("登陆成功")}
                    else {alert("用户不存在")}
                   }
                    });

后台：

查询数据库 select * from user where uname="+userName+" and pwd="+userPwd+"

看返回几行数据，如果为0 无用户，如果为>0用户存在

查询数据库的代码你可以百度下 我就不在这写了，如果不是这钟方式  你再问我

本回答被网友采纳

SQL：
IF EXISTS(SELECT 1 FROM [用户表] WHERE [用户名] = [传入的用户名])
RAISERROR('当前注册用户名已存在！', 16, 1)

您好:代码如下

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49

1.服务器控件后台方法:

//点击注册按钮
protected void ZhuCe_Click(object sender, EventArgs e)
{
string <a href="https://www.baidu.com/s?wd=sql&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">sql</a>1 = "<a href="https://www.baidu.com/s?wd=select&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">select</a> * <a href="https://www.baidu.com/s?wd=from&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">from</a> [ChangDiGuanLi].[dbo].[yonghu] <a href="https://www.baidu.com/s?wd=where&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">where</a> yonghu_name='" + yonghuname.Value + "'";
<a href="https://www.baidu.com/s?wd=if&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">if</a> (<a href="https://www.baidu.com/s?wd=Sql&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">Sql</a>Helper.ExecuteDataSet(<a href="https://www.baidu.com/s?wd=Sql&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">Sql</a>Helper.ECB_Platform, CommandType.Text, sql1, null).Tables[0].Rows.Count > 0)
{
ClientScript.RegisterStartupScript(ClientScript.GetType(), "myscript", "<script>alert('次用户名已经被注册，请换一个试试!');</script>");
}
else
{
string sql = "INSERT INTO [ChangDiGuanLi].[dbo].[yonghu] VALUES ('" + yonghuname.Value + "','" + yonghumima.Value + "','" + yonghuclass.Value + "','" + yonghumobile.Value + "',1,getDate())";
int num = SqlHelper.ExecuteNonQuery(SqlHelper.ECB_Platform, CommandType.Text, sql, null);
<a href="https://www.baidu.com/s?wd=if&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">if</a> (num == 1)
{
ClientScript.RegisterStartupScript(ClientScript.GetType(), "myscript", "<script>alert('注册成功');window.location.href='login.aspx';</script>");
}
else
{
ClientScript.RegisterStartupScript(ClientScript.GetType(), "myscript", "<script>alert('注册失败');</script>");
}
}
}

2.AJAX方法:

$(".zhuce").live("click", function () {
<a href="https://www.baidu.com/s?wd=if&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1Y3uWcsryDkm16dmH7BnARd0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6K1TL0qnfK1TL0z5HD0IgF_5y9YIZ0lQzqlpA-bmyt8mh7GuZR8mvqVQL7dugPYpyq8Q1D4PjR4PjRvPH0vPWD3P1bvnW6" target="_blank" class="baidu-highlight">if</a> (confirm("确定要注册吗")) {
$.ajax({
type: "POST",
contentType: "application/json",
url: "register.aspx/register",
async: true,
data: "{username:" + $(this).attr("username") + ",pwd:" + $(this).attr("pwd") + "}",
dataType: "json",
success: function (result) {
if (result.d > 1) {
alert('注册成功');
} else {
alert('注册失败');
}
}
});
}
else {
return false;
}
});