Question

this is my snippet , please help me why the con .open is not working inside the function tabledel

i want to delete the table once i press the button , the connection gets opened for the first time but couldnt open it for the second time inside the function tabledel

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 WFA_CREATE_DELETE
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        OleDbConnection con = new OleDbConnection(@"PROVIDER=Microsoft.ACE.OLEDB.12.0; Data Source=C:/Users/Dinesh/Documents/Database3.accdb");
        OleDbDataAdapter ea = new OleDbDataAdapter();
        DataSet dsl;
        DataSet esl;

        private void Form1_Load(object sender, EventArgs e)
        {
            OleDbDataAdapter da = new OleDbDataAdapter();
            dsl = new DataSet();
            con.Open();

            DataTable table2 = con.GetSchema("tables");

            MessageBox.Show("Database Open");

            dataGridView1.DataSource = table2;

            con.Close();
            con.Dispose();
        }

        public void Tabledel()
        {
            int a = 0, d = 0, count, itr;

            count = dataGridView1.RowCount;
            itr = dataGridView1.ColumnCount;

            while (a < count)
            {
                for (d = 0; d < itr; d++)
                {
                    if (dataGridView1.Rows[a].Cells[d].Value.ToString() == textBox1.Text)
                    {

                        MessageBox.Show("table exists");
                        esl = new DataSet();
                        string vsql = "drop table '" + textBox1.Text + "'";
                        ea = new System.Data.OleDb.OleDbDataAdapter(vsql, con);
                        OleDbCommand cmdea = new OleDbCommand(vsql, con);
                        //cmdea.Connection = con;

                        con.Open();
                        cmdea.ExecuteNonQuery();
                        MessageBox.Show("table dropped");
                        con.Close();
                        con.Dispose();
                    }
                }

                a++;
            }
        }

        private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }

        public void button1_Click(object sender, EventArgs e)
        {
           Tabledel();


        }

    }
}

link

Answer 1

As I see you get this error:

The ConnectionString property has not been initialized.

May be you will create (dispose) your connection in somewhere else (except in form class global variable), so I suggest to set connection string explicitly (With recreating connection):

con = new OleDbConnection(
      @"PROVIDER=Microsoft.ACE.OLEDB.12.0; Data Source=C:/Users/Dinesh/Documents/Database3.accdb");

con.Open();

Anyway it wasn’t hard to include main part of your code here in SO.