C# Populate DataTable from Access?

I am having some trouble binding a datatable returned from a query to a datagridview. I believe the problem is in the GetTableFromQuery(...) method. Debug shows no table rows being populated after the query execution. The table contains no data in the datagridview after binding the datasource.

Here's the query and call to database operation.

private void buttonFilterCustomers_Click(object sender, EventArgs e)

{

DataTable dt = new DataTable();

string query = "SELECT * FROM Customers WHERE '" + comboBoxFilterCustomers.SelectedItem.ToString() + "' = '" + textBoxFilterValueCustomers.Text.ToString() + "'";

dt = DatabaseOperations.GetTableFromQuery(query, null, CommandType.Text);

dataGridViewCustomers.DataSource = dt;

}

Here's the database operation. Sorry for the lack of indentation.

public static DataTable GetTableFromQuery(string query, Dictionary<string, object> parameters, CommandType commandType)

{

DataTable dataTable = new DataTable();

using (OleDbConnection conn = GetConnection())

{

using (OleDbCommand cmd = new OleDbCommand(query, conn))

{

cmd.CommandType = commandType;

if (parameters != null)

{

foreach (KeyValuePair<string, object> parameter in parameters)

{

cmd.Parameters.AddWithValue(parameter.Key, parameter.Value);

}

}

using (OleDbDataAdapter adapter = new OleDbDataAdapter(cmd))

{

adapter.Fill(dataTable);

}

}

}

return dataTable;

}