Latest SQL Helper Class for WPF (LINQ or ADO.NET)

public class SQLHelper
   {
       private SqlConnection _objConnection;
       private SqlCommand _objCommand;
       private SqlTransaction _sqlTrans;
       private string _connectionString;
       private String[] _tables = { "Table", "Table1", "Table2", "Table3", "Table4", "Table5", "Table6", "Table7", "Table8" };
       public SQLHelper()
       {
           _connectionString = WebConfigurationManager.ConnectionStrings["Connect"].ToString();
           _objConnection = new SqlConnection(_connectionString);
           _objCommand = new SqlCommand();
           _objCommand.CommandTimeout = 40000;
       }
       private void Open()
       {
           try
           {
               if (_objConnection.State != ConnectionState.Open)
                   _objConnection.Open();
               if (_objCommand == null)
                   _objCommand = new SqlCommand();
               _objCommand.Connection = _objConnection;
           }
           catch (Exception ex)
           {
               Close();
               throw new ApplicationException("Error", ex);
           }
       }
       private void Close()
       {
           try
           {
               _objCommand.Dispose();
               if (_sqlTrans == null)
               {
                   if (_objConnection.State != ConnectionState.Closed)
                       _objConnection.Close();
               }
           }
           catch(Exception ex)
           {
               throw new ApplicationException("Error", ex);
           }
       }
       public string StoreProcedureName
       {
           get
           {
               if (_objCommand != null)
                   return _objCommand.CommandText;
               else
                   return null;
           }
           set
           {
               if (_objCommand == null)
               {
                   _objCommand = new SqlCommand();
               }
               _objCommand.Parameters.Clear();
               _objCommand.CommandText = value;
               _objCommand.CommandType = CommandType.StoredProcedure;
           }
       }
       public DataSet ExecDataSet()
       {
           DataSet dataSet = new DataSet();
           try
           {
               Open();
               SqlDataAdapter dataAdapter = new SqlDataAdapter(_objCommand);
               dataAdapter.Fill(dataSet);
               return dataSet;
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error:ExecDataSet", ex);
           }
           finally
           {
               Close();
           }
       }
       public void ExecDataSet(DataSet dataSet, string[] mapping)
       {
           try
           {
               Open();
               SqlDataAdapter dataAdapter = new SqlDataAdapter(_objCommand);
               for (int i = 0; i < mapping.Length; i++)
               {
                   dataAdapter.TableMappings.Add(_tables[i], mapping[i]);
               }
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error:ExecDataSet(DataSet dataSet, string[] mapping)",ex)
           }
           finally
           {
               Close();
           }
       }
       public void ExecDataSet(T dataSet) where T : DataSet
       {
           try
           {
               Open();
               SqlDataAdapter dataAdapter = new SqlDataAdapter(_objCommand);
               dataAdapter.Fill(dataSet);
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error ExecDataSet(T dataSet) ", ex);
           }
           finally
           {
               if (_sqlTrans != null)
                   Close();
           }
       }
       public DataTable ExecDataTable()
       {
           DataTable dataTable = new DataTable();
           try
           {
               Open();
               SqlDataAdapter dataAdapter = new SqlDataAdapter(_objCommand);
               dataAdapter.Fill(dataTable);
               return dataTable;
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error ExecDataTable()", ex);
           }
           finally
           {
               Close();
           }
       }
       public SqlParameterCollection Parameters
       {
           get
           {
               return _objCommand.Parameters;
           }
       }
       public int ExecDML()
       {
           int intCount;
           try
           {
               Open();
               intCount = _objCommand.ExecuteNonQuery();
           }
           catch (Exception ex)
           {
               intCount = 0;
               throw new ApplicationException("Error ExecDML", ex);
           }
           finally
           {
               Close();
           }
           return intCount;
       }
       public SqlDataReader ExecReader()
       {
           SqlDataReader dataReader = null;
           try
           {
               Open();
               dataReader = _objCommand.ExecuteReader();
               return dataReader;
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error ExecReader",ex)
           }
           finally
           {
               Close();
           }
       }
       public object ExecScalar()
       {
           try
           {
               Open();
               return _objCommand.ExecuteScalar();
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error ExecScalar",ex)
           }
           finally
           {
               Close();
           }
       }
       public void BeginTransaction()
       {
           try
           {
               Open();
               _sqlTrans = this._objConnection.BeginTransaction(IsolationLevel.ReadCommitted);
               _objCommand.Transaction = _sqlTrans;
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error BeginTransaction", ex);
           }
       }
       public void RollBack()
       {
           try
           {
               if (_sqlTrans != null)
               {
                   _sqlTrans.Rollback();
                   _sqlTrans = null;
               }
               Close();
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error RollBack()", ex);
           }
       }
       public void Commit()
       {
           try
           {
               if (_sqlTrans != null)
               {
                   _sqlTrans.Commit();
                   _sqlTrans = null;
               }
               Close();
           }
           catch (Exception ex)
           {
               throw new ApplicationException("Error Commit()", ex);
           }
       }

   }