How to Fix datagrid with The ConnectionString property has not been initialized

Question

I have a sub function or I don't what its term really is and here's the code:

Public Sub GridMiner()
  Try
    Con.Open()
    sql = "Select roomnumber AS [Room], [end] AS [Check out at], hours as [on] FROM rooms where [end] between ? and ?"
    cmd = New OleDb.OleDbCommand(sql, Con)
    cmd.Parameters.AddWithValue("@from", Now.AddDays(0).ToString("MM/dd/yyyy"))
    cmd.Parameters.AddWithValue("@to", Now.AddDays(1).ToString("MM/dd/yyyy"))

    da = New OleDb.OleDbDataAdapter(cmd)
    da.Fill(ds)

    gridSummary.DataSource = ds.Tables(0) 
    ds = Nothing
    da = Nothing
    Con.Close()
    Con.Dispose()
  Catch ex As Exception
    MsgBox(ex.Message)
  End Try
End Sub

that code works perfectly. Now I have created a refresh button to refresh its data. However, I got a following error:

The ConnectionString property has not been initialized.

Now I have debug it and it points me to con.Open() line. This is my button code:

Private Sub btnRefresh_Click(sender As Object, e As EventArgs) Handles btnRefresh.Click
  GridMiner()
End Sub

and I also try to write the code again inside my button:

Private Sub btnRefresh_Click(sender As Object, e As EventArgs) Handles btnRefresh.Click
  con.Open()
  sql = "Select roomnumber AS [Room], [end] AS [Check out at], hours as [on] FROM rooms where [end] between ? and ?"
  cmd = New OleDb.OleDbCommand(sql, con)
  cmd.Parameters.AddWithValue("@from", Now.AddDays(0).ToString("MM/dd/yyyy"))
  cmd.Parameters.AddWithValue("@to", Now.AddDays(1).ToString("MM/dd/yyyy"))

  da = New OleDb.OleDbDataAdapter(cmd)
  da.Fill(ds)

  gridSummary.DataSource = ds.Tables(0)
  ds = Nothing
  da = Nothing
  con.Close()
  con.Dispose()
End Sub

UPDATED:

Hi I updated my code, and removed con.dispose() however, when I removed it it says.

Value can't be null Parameter name: dataSet

Then I removed

ds = Nothing

Then it works, however it added the information instead of refreshing it to the datagrid.

Answer 1

You're disposing the connection, thus the error.

Remove:

Con.Dispose().