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");

else{

if (type.HasAttribute<DBTableNameAttribute>())

return type.GetAttribute<DBTableNameAttribute>().Name;

else

return type.Name;

　　}

}

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 UniqueColumnAttribute

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";

insertstr+=" select @@identity"

SqlHelper link = new SqlHelper();

int r=  link.UpdateDataBase(insertstr);

if(r>0)     {

o.Id=r;

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 =string.Format( "delete from {0} where id={1}",tablename,id)

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;

}

}

if(!string.IsNullOrEmpty(str))

{

SqlHelper link = new SqlHelper();

int r = link.UpdateDataBase(str);

return true;

}

return false;

}

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)) )                 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;

}

}

}