Question

我一直在研究这个问题。我正在尝试通过自定义程序向访问数据库添加值。我没有任何语法错误或任何我可以看错的东西，但我是一个新手。任何帮助将非常感激。我有一些脏代码，我正在搞乱，但评论出来。请帮忙！谢谢你们和男孩们。

我正在使用AMD Win 10 Visual Studio 2015 访问2016

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.OleDb;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class frmNewClient : Form
    {
        OleDbConnection connect = new OleDbConnection();


        public frmNewClient()
        {
            InitializeComponent();


        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }

        private void cmdClientInput_Click(object sender, EventArgs e)
        {

        string CompanyName = txtCCOMPANYNAME.Text;
        string ContactName = txtCCONTACTNAME.Text;
        string Street = txtCSTREET.Text;
        string City = txtCCITY.Text;
        string State = txtCSTATE.Text;
        string ZIP = txtCZIP.Text;
        string Phone1 = txtCPHONE1.Text;
        string Phone2 = txtCPHONE2.Text;
        string Email = txtCEMAIL.Text;
        string Notes = txtCNOTES.Text;
        connect.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=c:\\lafiammadb.accdb;Persist Security Info=False";
        OleDbCommand cmd = new OleDbCommand("INSERT Into Clients(CompanyName, ContactName, Street, City, State, ZIP, Phone1, Phone2, Email, Notes)" + "values(@CompanyName, @ContactName, @Street, @City, @State, @ZIP, @Phone1, @Phone2, @Email, @Notes)", connect);
        if (connect.State == ConnectionState.Open)
        {
            cmd.Parameters.Add("@CompanyName", OleDbType.Char, 20).Value = CompanyName;
            cmd.Parameters.Add("@ContactName", OleDbType.Char, 20).Value = ContactName;
            cmd.Parameters.Add("@Street", OleDbType.Char, 20).Value = Street;
            cmd.Parameters.Add("@City", OleDbType.Char, 20).Value = City;
            cmd.Parameters.Add("@State", OleDbType.Char, 20).Value = State;
            cmd.Parameters.Add("@ZIP", OleDbType.Char, 20).Value = ZIP;
            cmd.Parameters.Add("@Phone1", OleDbType.Char, 20).Value = Phone1;
            cmd.Parameters.Add("@Phone2", OleDbType.Char, 20).Value = Phone2;
            cmd.Parameters.Add("@Email", OleDbType.Char, 20).Value = Email;
            cmd.Parameters.Add("@Notes", OleDbType.Char, 20).Value = Notes;
            try
            {
                cmd.ExecuteNonQuery();
                MessageBox.Show("Data Added To Database");
                txtCCOMPANYNAME.Text = "";
                txtCCONTACTNAME.Text = "";
                txtCSTREET.Text = "";
                txtCCITY.Text = "";
                txtCSTATE.Text = "";
                txtCZIP.Text = "";
                txtCPHONE1.Text = "";
                txtCPHONE2.Text = "";
                txtCEMAIL.Text = "";
                txtCNOTES.Text = "";

            }
            catch (Exception expe)
            {
                MessageBox.Show(expe.Source);
                connect.Close();
            }

        }
        else
        {
            MessageBox.Show("Connection Failed");

        }
        //connect.Open();


        //OleDbCommand cmd = new OleDbCommand(q);
        //cmd.Parameters.AddWithValue("@CompanyName", CompanyName);
        //cmd.Parameters.AddWithValue("@ContactName", ContactName);
        //cmd.Parameters.AddWithValue("@Street", Street);
        //cmd.Parameters.AddWithValue("@City", City);
        //cmd.Parameters.AddWithValue("@ZIP", ZIP);
        //cmd.Parameters.AddWithValue("@Phone1", Phone1);
        //cmd.Parameters.AddWithValue("@Phone2", Phone2);
        //cmd.Parameters.AddWithValue("@Email", Email);
        //cmd.Parameters.AddWithValue("@Notes", Notes);
        //cmd.ExecuteNonQuery();


        //OleDbCommand CmdSql = new OleDbCommand("Insert into [clients](Company Name, Contact Name, Street, City, State, Zip, Phone1, Phone2, Email, Notes)



    }
}
}

Answer 1

问题在于：

if (connect.State == ConnectionState.Open)

您正在检查连接是否已打开，但实际上您并未打开连接。在检查之前，您需要Open您的连接。你可以尝试这样：

if (connect.State == ConnectionState.Closed)
{
    connect.Open();
}

旁注：

在处理连接时，您可以考虑使用using statament。

Answer 2

这一行给出了问题if (connect.State == ConnectionState.Open)。你真正想要做的是检查连接是否已关闭，然后打开它：

if (connect.State == ConnectionState.Closed)
{
  connect.Open();
  //Do Some work
}

但是我建议您使用using块来保证对象的正确处理。

来自 MSDN

要确保始终关闭连接，请打开using块内部的连接，如以下代码片段所示。这样做可确保在代码退出块时自动关闭连接。

using(OleDbConnection connect = new OleDbConnection(connectionString))
{
  connect.Open();
  //Do some work
}// Here it will automatically call Dispose();

由于OleDbConnection类实现了IDisposable。因此，您可以直接使用Dispose()方法，并且不会被要求致电connect.Close();

Visual Studio C＃到MS Access连接失败

2 个答案: