原创最简单的ORM例子

这个仅是为了培训做的一个小例子

 public class DB     {         public static string GetClassName(Type type)         {             if (type == null)                 throw new ArgumentException("参数type不能为空");

            //if (type.HasAttribute<AliasAttribute>())             //    return type.GetAttribute<AliasAttribute>().Name.ToLower();             //else                 return type.Name.ToLower();         }         public static T AddObject<T>(T o) where T :class          {                     string tablename = GetClassName(typeof(T));             string fieldName;             object fieldValue;             string[] fieldNames;             object[] fieldValues;             System.Reflection.PropertyInfo[] Props = typeof(T).GetProperties();             fieldNames=new string[Props.Length ];             fieldValues =new object [Props.Length ];             string checkstr = "";             for (int i = 0; i < Props.Length; i++)             {                 fieldName = Props[i].Name;                 fieldValue = Props[i].GetValue(o, null);                 if (fieldValue == null)                     continue;                 fieldValue = CommonFunction.SafeSQL(fieldValue.ToString());                 fieldNames[i] = fieldName;                 fieldValues[i] = fieldValue;                 object[] attributes = Props[i].GetCustomAttributes(false);                 foreach (Attribute a in attributes)                 {                     //判断Attribute 中是否 为 ImgAttribute                     if (a is UniqueColumnAttribute)                     {                         checkstr = "not exists(select * from " +tablename + " where " + fieldName  + "=‘" + fieldValue + "‘)";                     }                 }             }             if (checkstr != "")             {                 checkstr = "if("+checkstr +")";             }             string insert = "" ,tail="";             insert = "insert into " + tablename + " (";                         tail = "values(";             for (int i = 0; i < Props.Length; i++)             {                 fieldName = fieldNames[i] ;

                if (fieldName.ToUpper() == "ID") continue;

                object  _fieldValue = fieldValues[i];                 if (_fieldValue == null)                 { }                 else                 {

                    insert += fieldName + ",";

                    tail += "‘" + _fieldValue + "‘,";                 }             }             insert = insert.Remove(insert.Length - 1);             tail = tail.Remove(tail.Length - 1);             string insertstr = insert + ")" + " " + tail + ")";             if (checkstr != "")                 insertstr = checkstr +"begin "+ insertstr+" end";             SqlHelper link = new SqlHelper();           int r=  link.UpdateDataBase(insertstr);

            //if (o.GetType == typeof(KeywordCat))             //{

            //}             //else if (o.GetType == typeof(Keyword))             //{             //}             //else             //{

            //}             if(r>0)             return o;         return null;         }         public static bool  DelObject<T>( int id) where T : class         {             if (id == 0) return false;             string tablename = GetClassName(typeof(T));             string insert = "";             insert = "delete from " + tablename + " where id="+id.ToString();             SqlHelper link = new SqlHelper();             int r = link.UpdateDataBase(insert);             return true;         }         public static bool  DelObject<T>(T o) where T : class         {             string tablename = GetClassName(typeof(T));             string fieldName;             object fieldValue;             string[] fieldNames;             object[] fieldValues;             System.Reflection.PropertyInfo[] Props = typeof(T).GetProperties();             fieldNames = new string[Props.Length];             fieldValues = new object[Props.Length];             for (int i = 0; i < Props.Length; i++)             {                 fieldName = Props[i].Name;                 fieldValue = Props[i].GetValue(o, null);                 fieldNames[i] = fieldName;                 fieldValues[i] = fieldValue;             }             string str="";             for (int i = 0; i < Props.Length; i++)             {                 fieldName = fieldNames[i];                 string _fieldValue = fieldValues[i].ToString();                 if (fieldName.ToUpper() == "ID")                 {                     str = "delete from " + tablename + " where id=" + _fieldValue ;                               break;                 }                             }             SqlHelper link = new SqlHelper();             int r = link.UpdateDataBase(str);             return true;                                 }         public static bool UpdateObject<T>(T o) where T : class         {             string tablename = GetClassName(typeof(T));             string fieldName;             object fieldValue;             string[] fieldNames;             object[] fieldValues;             System.Reflection.PropertyInfo[] Props = typeof(T).GetProperties();             fieldNames = new string[Props.Length];             fieldValues = new object[Props.Length];             for (int i = 0; i < Props.Length; i++)             {                 if (Props[i].DeclaringType.IsValueType)                 {                     fieldName = Props[i].Name;                     fieldValue = Props[i].GetValue(o, null);                     fieldNames[i] = fieldName;                     fieldValues[i] = fieldValue;                 }                 else                 {                     fieldNames[i] = null; fieldValues[i] = null;                 }             }             string str = "update "+tablename +" set ",where=" where id=";             int id = 0;             for (int i = 0; i < Props.Length; i++)             {                 fieldName = fieldNames[i];                 object  _fieldValue = fieldValues[i] ;                 if (fieldName == null) continue;                 if (fieldName.ToUpper() == "ID")                 {                     if (_fieldValue == null)                     {                     }                     else                     {                         int.TryParse(_fieldValue.ToString(), out id);                         //str = "delete from " + tablename + " where id=" + _fieldValue;                         where += id.ToString();                     }                     //break;                 }                 else                 {                     if (_fieldValue == null)                     {                     }                     else                     str += fieldName +  "=‘" + _fieldValue.ToString() + "‘,";                 }

            }             if (id <= 0) return false;             str = str.Remove(str.Length - 1);             str += where;             SqlHelper link = new SqlHelper();             int r = link.UpdateDataBase(str);             return true;

        }         public static T SelObject<T>(int id) where T : class         {             if (id == 0) return null ;             string tablename = GetClassName(typeof(T));             string insert = "";             insert = "select * from " + tablename + " where id=" + id.ToString();             SqlHelper link = new SqlHelper();             DataTable dt = link.SelectDataBase(insert);             if (dt == null || dt.Rows.Count == 0) return null;             Type type = typeof(T);             Object obj = type.Assembly.CreateInstance(type.FullName);             System.Reflection.PropertyInfo[] Props = typeof(T).GetProperties();                        for (int i = 0; i < Props.Length; i++)             {                 Props[i].SetValue(obj, dt.Rows[0][Props[i].Name], null);             }             return (T)obj;         }         public static T SelObject<T>(BaseQuery query  ) where T : class         {             if (query==null )                 return null;             string tablename = GetClassName(typeof(T));             if (tablename.EndsWith("Query"))                 tablename = tablename.Replace("Query","");             string fieldName;             object fieldValue;             string[] fieldNames;             object[] fieldValues;

            System.Reflection.PropertyInfo[] Props = query.GetType().GetProperties();             fieldNames = new string[Props.Length];             fieldValues = new object[Props.Length];             for (int i = 0; i < Props.Length; i++)             {                 fieldName = Props[i].Name;                 fieldValue = Props[i].GetValue(query, null);                 fieldNames[i] = fieldName;                 fieldValues[i] = fieldValue;             }             string insert = "",where="1=1";             insert = "select * from " + tablename + " where "  ;             int id = 0;             for (int i = 0; i < Props.Length; i++)             {                 fieldName = fieldNames[i];                 object _fieldValue = fieldValues[i];                 if (fieldName.ToUpper() == "ID")                 {                     if (_fieldValue == null)                     {                     }                     else                     {                         int.TryParse(_fieldValue.ToString(), out id);                         //str = "delete from " + tablename + " where id=" + _fieldValue;                         where +="Id="+ id.ToString();                     }                     //break;                 }                 else                 {                     if (_fieldValue == null)                     {                     }                     else                     {                         if (string.IsNullOrEmpty(_fieldValue.ToString()))                         { }                         else                         where += " and " + fieldName + "=‘" + _fieldValue.ToString() + "‘";                     }                 }

            }

            insert = insert + where;             SqlHelper link = new SqlHelper();             DataTable dt = link.SelectDataBase(insert);             if (dt == null || dt.Rows.Count == 0) return null;             Type type = typeof(T);             Object obj = type.Assembly.CreateInstance(type.FullName );             System.Reflection.PropertyInfo[] Props2 = typeof(T).GetProperties();

            for (int i = 0; i < Props2.Length; i++)             {                 Props2[i].SetValue(obj, dt.Rows[0][Props2[i].Name], null);             }             return (T)obj;         }         public static T SelObject<T>(string where) where T : class         {             if (string.IsNullOrEmpty(where))//==null )                 return null;

            string tablename = GetClassName(typeof(T));             string insert = "";             insert = "select * from " + tablename + " where " + where;             SqlHelper link = new SqlHelper();             DataTable dt = link.SelectDataBase(insert);             if (dt == null || dt.Rows.Count == 0) return null;             Type type = typeof(T);             Object obj = type.Assembly.CreateInstance(type.FullName);             System.Reflection.PropertyInfo[] Props = typeof(T).GetProperties();

            for (int i = 0; i < Props.Length; i++)             {                 Props[i].SetValue(obj, dt.Rows[0][Props[i].Name], null);             }             return (T)obj;         }

        public static List<T> ListObjects<T>(string where) where T : class         {             try             {                 if (string.IsNullOrEmpty(where))                 where = "1=1";                 string tablename = GetClassName(typeof(T));                 string insert = "";                 insert = "select * from " + tablename + " where " + where;                 SqlHelper link = new SqlHelper();                 DataTable dt = link.SelectDataBase(insert);                 if (dt == null || dt.Rows.Count == 0) return null;                 Type type = typeof(T);                 List<T> list = new List<T>();                 for (int row = 0; row < dt.Rows.Count; row++)                 {                     Object obj = type.Assembly.CreateInstance(type.FullName );                     System.Reflection.PropertyInfo[] Props = typeof(T).GetProperties();

                    for (int i = 0; i < Props.Length; i++)                     {                         Props[i].SetValue(obj, dt.Rows[row][Props[i].Name], null);                     }                     list.Add((T)obj);                 }                 return list;             }             catch             {                 return null;             }         }     }

原创最简单的ORM例子

原文：http://www.cnblogs.com/zhshlimi/p/4907162.html