Abstract Data Access Layer Design

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;

namespace XPeriment.DataAccessTasks
{
    public class QueryTask:FieldSetTask
    {
        private string condition = "";
        private List<JoinData> joins = new List<JoinData>();

        public List<JoinData> Joins
        {
            get
            {
                return joins;
            }
            set
            {
                joins = value;
            }
        }

        public string Condition
        {
            get
            {
                return condition;
            }
            set
            {
                condition = value;
            }
        }

        public QueryTask(string baseTable)
            : base(baseTable)
        {

        }

        public void Select(string fieldName, string fieldAlias)
        {
            Fields.Add(fieldName, new FieldData(fieldName, fieldAlias));
        }

        public void Select(params string[] fields)
        {
            foreach (string s in fields)
                Fields.Add(s, new FieldData(s, ""));
        }

        public void InnerJoin(string tableName, string joinCondition)
        {
            joins.Add(new JoinData(tableName, joinCondition));
        }

        public void LeftJoin(string tableName, string joinCondition)
        {
            joins.Add(new JoinData("LEFT", tableName, joinCondition));
        }

        public void RightJoin(string tableName, string joinCondition)
        {
            joins.Add(new JoinData("RIGHT", tableName, joinCondition));
        }

        public void OutterJoin(string tableName, string joinCondition)
        {
            joins.Add(new JoinData("OUTTER", tableName, joinCondition));            
        }

        public void CrossJoin(string tableName, string joinCondition)
        {
            joins.Add(new JoinData("CROSS", tableName, joinCondition));
        }

        public void Where(string filterCondition)
        {
            condition = filterCondition;
        }

        public DataTable Execute()
        {
            return Performer.Run(this);   
        }
    }
}