error : Connection Property has not been initialized

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 WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        System.Data.OleDb.OleDbConnection con;
        DataSet ds1;
        System.Data.OleDb.OleDbDataAdapter da;

        int MaxRows = 0;
        int inc = 0;

        private void Form1_Load(object sender, EventArgs e)
        {
            con = new System.Data.OleDb.OleDbConnection();
            ds1 = new DataSet();

            con.ConnectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:/MyWorkers1.mdb";

            string sql = "SELECT * from tblWorkers";
            da = new System.Data.OleDb.OleDbDataAdapter(sql, con);

            con.Open();
            da.Fill(ds1, "MyWorkers1");
            NavigateRecords();
          开发者_JAVA技巧  MaxRows = ds1.Tables["MyWorkers1"].Rows.Count;
            //MaxRows = ds1.Tables["MyWorkers1"].Rows[inc];
            //MessageBox.Show("Database open");

            con.Close();
            //MessageBox.Show("Database close");

            con.Dispose();
        }

        private void NavigateRecords()
        {
            DataRow drow = ds1.Tables["MyWorkers1"].Rows[inc];
            textBox1.Text = drow.ItemArray.GetValue(0).ToString();
            textBox2.Text = drow.ItemArray.GetValue(1).ToString();
            textBox3.Text = drow.ItemArray.GetValue(2).ToString();
        }

        private void btnNext_Click(object sender, EventArgs e)
        {
            if (inc != MaxRows - 1)
            {
                inc++;
                NavigateRecords();
            }
            else
            {
                MessageBox.Show("No More Records");
            }
        }

        private void btnPrevious_Click(object sender, EventArgs e)
        {
            if (inc > 0)
            {
                inc--;
                NavigateRecords();
            }
            else
            {
                MessageBox.Show("First Record");
            }
        }

        private void btnFirst_Click(object sender, EventArgs e)
        {

            if (inc != 0)
            {
                inc = 0;
                NavigateRecords();
            }
        }

        private void btnLast_Click(object sender, EventArgs e)
        {
            if (inc != MaxRows - 1)
            {
                inc = MaxRows - 1;
                NavigateRecords();
            }
        }

        private void btnAddNew_Click(object sender, EventArgs e)
        {
            textBox1.Clear();
            textBox2.Clear();
            textBox3.Clear();
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            System.Data.OleDb.OleDbCommandBuilder cb;
            cb = new System.Data.OleDb.OleDbCommandBuilder(da);

            DataRow drow = ds1.Tables["MyWorkers1"].NewRow();

            drow[0] = textBox1.Text;
            drow[1] = textBox2.Text;
            drow[2] = textBox3.Text;

            ds1.Tables["MyWorkers1"].Rows.Add(drow);

            MaxRows = MaxRows + 1;
            inc = MaxRows - 1;

            da.Update(ds1, "MyWorkers1");

            MessageBox.Show("Record / Entry Added");
        }       

    }
}

When I run this it shows an error like "Invalid Operation - Exception Unhandled connection property has not been initialized."

What is wrong?

---

I'm not an expert, but try

con = new System.Data.OleDb.OleDbConnection(you_connection_string);

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You can check if your ConnectionString is valid or not here : http://www.connectionstrings.com/

Notice that the Provider is different, regarding the .mdb version you are using (2007, 2000...)

By the way, would you like to try Source=D:\MyWorkers1.mdb instead of Source=D:/MyWorkers1 ? With a "\" instead of a "/".

---

I was working on the same example and figured that con.Dispose(); that is in the Form Load is not allowing da.Update(ds1, "MyWorkers1"); to update the record. So for the time being i have removed it, but it should better be moved to the Destroy/ Unload etc (i really don't know which is the correct event before closing the form)

---

The exception is very clear. The ConnectionString property has not been 'properly' set, when trying to call Open the SqlConnection object.

Have you tried creating one inside the web.config?