I have this code in Data Access Layer which is called by Application but its not returning any value from table, cant able to figure out where problem is.... any idea , comment will be appretiated

file..... webconfig

<configuration>
  <appSettings>
    <add key="DB"
         value="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\My Documents\db.mdb;Jet OLEDB:Database Locking Mode=1;Mode=16" />
  </appSettings>
    <connectionStrings />


file..... DAL.cs

public class DAL
{
    private String _ConnectionString;
    private OleDbCommand _SqlCommand;
    private OleDbConnection _Connection;
    private OleDbDataAdapter _SqlDataAdapter;
    private DataTable _ProductSearchResultTable;

    public DAL()
    {
        // todo:
    }

    public string ConnectionString()
    {
        _ConnectionString = ConfigurationManager.AppSettings["PlatinumDiamondDB"];
        _Connection = new OleDbConnection(_ConnectionString);
        return _ConnectionString ;
    }

    public DataTable SeacrhProduct(string shape, string miniPrice, string maxPrice)
    {

        _SqlCommand = new OleDbCommand();
        _SqlCommand.CommandText = "select * from product ";//where productprice between '" + miniPrice + "' AND '" + maxPrice +"'";
        _SqlCommand.Connection = _Connection;
        _SqlDataAdapter = new OleDbDataAdapter(_SqlCommand);
        _ProductSearchResultTable = new DataTable("ProductTable");
        _SqlDataAdapter.Fill(_ProductSearchResultTable);
        _Connection.Close();
        _SqlDataAdapter.Dispose();
        _Connection.Dispose();
    return _ProductSearchResultTable;
}

It would appear the problem is that you aren't using the same key name for the config and code.

Here's what you have in the config file:

Here's what you have in the code:
Those need to match.

-Peter