A generic loading of data in a DropDownList using caching mechanism

using System;
using System.Data;
using System.Data.SqlClient;

namespace DataAccessLayer
{
	/// <summary>
	/// Summary description for DataAccessLayer.
	/// This is a generic code for loading data from any database..
	/// One can also use OleDb for more generalized coding....
	
	/// </summary>
	public class DataAccess
	{
		//Private member
		private string strConn;
		private string strSelectCat;

		public DataAccess()
		{
			//
			// TODO: Add constructor logic here
			//Initialization 
			strConn=null;
			strSelectCat=null;
		}
		public DataAccess(string _strConn,string _strSelectCat)
		{
			//parameterized constructor;
			strConn=_strConn;
			strSelectCat=_strSelectCat;
		
		}
		//set connectionstring property 
		//this has been done just to show how property can be defined 
		
		public string ConnectionString
		{
			get
			{
				return strConn;
			}
			set
			{
				strConn=value;
			}
		
		}
		public string SelectStmOnCat
		{
			get
			{
				return strSelectCat;
			}
			set
			{
				strSelectCat=value;
			}
		}
		//PreCondition:Take Connection Object, Sql Query
		//PostCondition:Return DataTable containing Category list
		//Process:Fill Datatable with category from Northwind _db

		public DataTable LoadCategoryInDropDownList()
		{
			SqlConnection objConn=new SqlConnection(strConn);
			DataTable tblCategory =new DataTable();

			try
			{
				objConn.Open();
				//Using helps to dispose object as soon as 
				//required process gets complete
				using(SqlDataAdapter objAdpOnCat=new SqlDataAdapter(strSelectCat,objConn))
				{

					objAdpOnCat.Fill(tblCategory);
					
				}

			
			}
			catch(SqlException e)
			{
				throw new Exception("Invalid Connection Error Occured  "+e.Message);

			}
			finally
			{
				if(objConn.State.ToString()=="Open")
				{
					objConn.Dispose();
					objConn.Close();
					
				}
			}
			return tblCategory;
		
		
		}

	}
}