检查用户名是否存在

Question

我正在开始编码一个网站的工作，目前我正在做一个用户创建页面。所有的验证都工作得很好，但是我不确定要在checkUsername方法中输入什么才能验证用户名是否已经存在。下面是我的ASP.NET代码。

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
  <p>
  <asp:ValidationSummary ID="ValidationSummary1" runat="server" HeaderText="There were errors on the page:" />
  </p>
  <p>
      <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"  ControlToValidate="username" ErrorMessage="Username is required."> *</asp:RequiredFieldValidator>
  Enter Username <asp:TextBox ID="username" runat="server"></asp:TextBox>
     <asp:RegularExpressionValidator ID="RegularExpressionValidator1" runat="server" ControlToValidate="username" ErrorMessage="Username must be 4-10 letters or numbers." ValidationExpression="[a-zA-Z0-9]{4,10}" />
        <asp:CustomValidator ID="CustomValidator1" runat="server" controltovalidate="username" errormessage="Username is already in use." OnServerValidate="checkUsername" />
 </p>
 <p>
 Enter Password <asp:TextBox ID="entPWD" runat="server" TextMode="Password"></asp:TextBox>
        <asp:RegularExpressionValidator ID="RegularExpressionValidator2" runat="server" display="dynamic" ControlToValidate="entPWD" ErrorMessage="Password must contain one of the following: @#$%^&*/." ValidationExpression=".*[@#$%^&*/].*" />
        <asp:RegularExpressionValidator ID="RegularExpressionValidator3" runat="server" display="dynamic" ControlToValidate="entPWD" ErrorMessage="Password must be 6-12 characters." ValidationExpression="[^\s]{6,12}" />
 </p>
 <p>
 Confirm Password <asp:TextBox ID="confPWD" runat="server" TextMode="Password"></asp:TextBox>
        <asp:CompareValidator ID="CompareValidator1" runat="server" ControlToValidate="entPWD" ControlToCompare="confPWD" ErrorMessage="Passwords do not match." />
    </p>
    <asp:Button type="submit" ID="Button1" runat="server" Text="Submit" />
</asp:Content>

这是我的代码：

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    private bool checkUsername(string username)
    {
        string connString = "Data Source=serveraddress;Initial Catalog=database;User Id=username;Password=password;";
        string cmdText = "SELECT COUNT(*) FROM igs_users WHERE username = @username";

        using(SqlConnection conn = new SqlConnection(connString))
            {
            conn.Open();

            using(SqlCommand cmd = new SqlCommand(cmdText, conn))
                {
                cmd.Parameters.AddWithValue("@username", username);

                int count = (int)cmd.ExecuteScalar();

                return (count > 0);
                }
            }
    }
}

当我运行代码时，我得到以下错误消息：

Compiler Error Message: CS1061: 'ASP.default_aspx' does not contain a definition for 'checkUsername' and no extension method 'checkUsername' accepting a first argument of type 'ASP.default_aspx' could be found (are you missing a using directive or an assembly reference?)

我不确定我错在哪里。我在后面的代码中使用了System.Data.SqlClient；，还添加了对system.data.dll的引用。

任何帮助都将不胜感激！

Answer 1

自定义验证方法需要以下方法签名：

void checkUsername(object source, ServerValidateEventArgs args)

ServerValidateEventArgs将具有该值，而不是以字符串的形式传递用户名。

不是返回true或false进行验证，而是使用下面的代码：

args.IsValid = true; 

有关使用CustomValidators的更多信息，请参阅此页面：http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.customvalidator.onservervalidate(v=vs.80).aspx

Answer 2

尝试将方法设置为public而不是private。您的ASPX页面正在尝试访问它，但它是private。