how to connect databse for inserting,retriving

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VB

Imports System
Imports System.Data
Imports System.Data.SqlClient


Public Class AccOpeningPage
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
       

    End Sub

    Protected Sub btnsave_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnsave.Click
        Dim connetionString As String
        Dim cnn As SqlConnection
        Dim cmd As SqlCommand
        Dim sql As String

        connetionString = "Data Source=abc-PC;Initial Catalog=aaadb;User ID=sa;Password=sa123"
        cnn = New SqlConnection(connetionString)

            cnn.Open()
            MsgBox("Connection Open ! ")
            sql = "insert into CUSTHEAD(CUSTID, BRCODE, SALUTEFLG, GENDER, CNAME, DOB, AGE, FORHNAME, ADD1, ACCTYPE, ACCNO) VALUES (@CUSTID,@BRCODE, @SALUTEFLG, @GENDER, @CNAME, @DOB, @AGE, @FORHNAME,@ ADD1, @ACCTYPE, @ACCNO)"

        cmd = New SqlCommand(sql, cnn)
            With cmd.Parameters
                .AddWithValue("CUSTID", txtcustid.Text)
                .AddWithValue("BRCODE", txtbrcode.Text)
                .AddWithValue("SALUTEFLG", txtsalcode.Text)
                .AddWithValue("GENDER", optmfj.SelectedItem.ToString())
                .AddWithValue("CNAME", txtcname.Text)
                .AddWithValue("DOB", txtdob.Text)
                .AddWithValue("AGE", txtage.Text)
                .AddWithValue("FORHNAME", txtforhname.Text)
                .AddWithValue("ADD1", txtadd1.Text)
                .AddWithValue("ACCTYPE", txtacctype.Text)
                .AddWithValue("ACCNO", txtaccno.Text)
                cmd.ExecuteNonQuery()
            End With
            cnn.Close()
      

    End Sub
End Class

I get Error As

Must declare the scalar variable "@".

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: Must declare the scalar variable