c# - ExecuteNonQuery需要一个打开的可用连接.连接的当前状态是关闭的

我是c#新手。请协助!

我一直有以下错误:"ExecuteNonQuery需要一个打开的可用连接。连接的当前状态为关闭。"我也不能插入到我的数据库中。

下面是我的代码:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
namespace AzureSecureStore
{
    public partial class Client : Form
    {
        OleDbConnection vcon = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:'Users'SB18'Documents'Visual Studio 2010'Projects'AzureSecureStore'AzureSecureStore'AzcureSecureStore Database.accdb; Persist Security Info=False;");
        //OleDbConnection vcon = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:'Users'SB18'Documents'Visual Studio 2010'Projects'AzureSecureStore'AzureSecureStore'AzcureSecureStore Database.accdb");
        public Client()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
        }
        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
        }
        private void button5_Click(object sender, EventArgs e)
        {
        }
        private void button4_Click(object sender, EventArgs e)
        {
        }
        private void Client_Load(object sender, EventArgs e)
        {
            // TODO: This line of code loads data into the 'azcureSecureStore_DatabaseDataSet5.Client' table. You can move, or remove it, as needed.
            this.clientTableAdapter.Fill(this.azcureSecureStore_DatabaseDataSet5.Client);
            // TODO: This line of code loads data into the 'azcureSecureStore_DatabaseDataSet2.Client' table. You can move, or remove it, as needed.
            //this.clientTableAdapter.Fill(this.azcureSecureStore_DatabaseDataSet2.Client);
        }
        private void button2_Click(object sender, EventArgs e)
        {
            string ab = string.Format("insert into Client values({0}, '{1}', '{2}', {3}, {4}, '{5}')",
    textBox1.Text, textBox2.Text, int.Parse(textBox3.Text), int.Parse(textBox4.Text), textBox9.Text, int.Parse(textBox10.Text));
            OleDbCommand vcom = new OleDbCommand(ab, vcon);
            vcom.ExecuteNonQuery();
            MessageBox.Show("Data stored successfully");
            vcom.Dispose();
        }
        private void textBox1_TextChanged(object sender, EventArgs e)
        {
        }
    }
}

vcon.Open();
vcom.ExecuteNonQuery();

string connStr = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:'Users'SB18'Documents'Visual Studio 2010'Projects'AzureSecureStore'AzureSecureStore'AzcureSecureStore Database.accdb; Persist Security Info=False;";
string query = "INSERT INTO Client VALUES(@col1,@col2,@col3,@col4,@col5,@col6)";
using (OleDbConnection conn = new OleDbConnection(connStr))
{
    using (OleDbCommand comm = new OleDbCommand())
    {
        comm.Connection = conn;
        comm.CommandText = query;
        comm.CommandType = CommandType.Text;
        comm.Parameters.AddWithValue("@col1", textBox1.Text);
        comm.Parameters.AddWithValue("@col2", textBox2.Text);
        comm.Parameters.AddWithValue("@col3", int.Parse(textBox3.Text));
        comm.Parameters.AddWithValue("@col4", int.Parse(textBox4.Text));
        comm.Parameters.AddWithValue("@col5", textBox9.Text);
        comm.Parameters.AddWithValue("@col6", int.Parse(textBox10.Text));
        try
        {
            conn.Open();
            comm.ExecuteNonQuery();
            MessageBox.Show("Data stored successfully");
        }
        catch(OleDbException e)
        {
            MessageBox.Show(e.ToString());
        }
    }
}

vcon.Open();

vcom.ExecuteNonQuery();