Checking to see if username exists

[Jamby]

I am beginning work on coding a site and at the moment I am doing a user creation page. All the validation works fine, but I am unsure what to put into the checkUsername method in order to verify that the username does not already exist. Below is my ASP.NET code.\[code\]<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>\[/code\]And this is my Code Behind:\[code\]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); } } }}\[/code\]When I run the code, I get the following error message:\[code\]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?)\[/code\]Not sure where I am going wrong. I have using System.Data.SqlClient; in the Code Behind and also added a reference to system.data.dll.Any help would be appreciated!