Question

What is wrong with this code?
No error, but no results. My DataGridView_sent does not get filled.

Dim objConn As New System.Data.OracleClient.OracleConnection
Dim objCmd As New System.Data.OracleClient.OracleCommand
Dim dtAdapter As New System.Data.OracleClient.OracleDataAdapter

Dim ds As New DataSet
Dim strConnString, strSQL As String

strConnString = "Data Source=db;User Id=user;Password=pass;"
strSQL = "select * from table where sentdate between '" & date1 & "' and '" & date2 & "'"

 objConn.ConnectionString = strConnString
 With objCmd
     .Connection = objConn
     .CommandText = strSQL
     .CommandType = CommandType.Text
  End With
  dtAdapter.SelectCommand = objCmd

  dtAdapter.Fill(ds)
  DataGridView_sent.DataSource = ds

  dtAdapter = Nothing
  objConn.Close()
  objConn = Nothing

Answer 1

This is probably caused by incorrect representation of dates.
You should use parametrized queries and let the Oracle Provider render in the correct mode your date fields values

....
strSQL = "select * from table where sentdate between :date1 and :date2" 
objConn.ConnectionString = strConnString 
With objCmd 
   .Connection = objConn 
   .CommandText = strSQL 
   .CommandType = CommandType.Text 
   .Parameters.AddWithValue(":date1", Convert.ToDateTime(date1));
   .Parameters.AddWithValue(":date2", Convert.ToDateTime(date2));
End With 
dtAdapter.SelectCommand = objCmd 
.....