一个简单的ORM制作(SQL帮助类)

一个简单的ORM制作大概需要以下几个类：
SQL执行类
CURD操作类
其他酱油类

先从SQL执行类说起，可能会涉及数据库的迁移等问题，所以需要定义一个接口以方便迁移到其他数据库，





事务没提供命名，若需要命名可修改为可变参数，IHelper代码如下：

internal interface IHelper:IDisposable
{
int ExecuteQuery(string txt, IEnumerable<IDataParameter> ps, bool issp);//用于执行INSERT,UPDATE
object ExectueScalar(string tex, IEnumerable<IDataParameter> ps, bool issp);//执行COUT()
IDataReader ExectueReader(string tex, IEnumerable<IDataParameter> ps, bool issp);//执行SELECT
void BegTran();//开始事务
void RollBack();//回滚
void Commit();//提交
string CreateSql(string select, string tbname, string where, string orderby, int size, int index);//数据库的不同,产生的SQL也可能不同,所以必须提供不同的生成方案
IDataParameter Cp(string name, object value);//创建参数
string GetIdStr { get; }//获取INSERT产生ID的SQL代码,可能各个数据库不太相同
string ParStr(string name);//参数标示符,比如MSSQL:@NAME, MYSQL:?NAME,ODBC直接返回?无命名
}

以上为我个人能思考到的数据库差异和基础功能，若有其他请大家指教

通用MsSql帮助类代码如下：

class Mssql:IHelper
{
SqlCommand cmd;
SqlConnection con;
SqlTransaction tran;
internal Mssql(string constr)
{
con = new SqlConnection(constr);//test
cmd = new SqlCommand();
cmd.Connection = con;
}
void SetCmd(string str, IEnumerable<IDataParameter> ps, bool issp)
{
cmd.CommandText = str;
cmd.CommandType = issp ? CommandType.StoredProcedure : CommandType.Text;
cmd.Parameters.Clear();
foreach (var n in ps) { cmd.Parameters.Add(n); }
}
void CloseCon(){if (con.State == ConnectionState.Open) { con.Close(); }}
void OpenCon() { if (con.State == ConnectionState.Closed) { con.Open(); } }
int IHelper.ExecuteQuery(string str, IEnumerable<IDataParameter> ps, bool issp)
{
try
{
SetCmd(str, ps, issp);
OpenCon();
return cmd.ExecuteNonQuery();
}
finally{if(tran==null){CloseCon();}}
}
object IHelper.ExectueScalar(string str, IEnumerable<IDataParameter> ps, bool issp)
{
try
{
SetCmd(str, ps, issp);
OpenCon();
return cmd.ExecuteScalar();
}
finally{if(tran==null){CloseCon();}}
}
IDataReader IHelper.ExectueReader(string str, IEnumerable<IDataParameter> ps, bool issp)
{
SetCmd(str, ps, issp);
OpenCon();
return cmd.ExecuteReader(tran==null?CommandBehavior.CloseConnection:CommandBehavior.Default);
}
void IHelper.BegTran() { OpenCon(); tran = con.BeginTransaction(); cmd.Transaction = tran; }
void IHelper.Commit() { if (tran != null) { tran.Commit(); con.Close(); tran = null; } }
void IHelper.RollBack() { if (tran != null) { tran.Rollback(); con.Close(); tran = null; } }
string IHelper.CreateSql(string select, string tbname, string where, string orderby, int size, int index)
{
StringBuilder sb = new StringBuilder();//分页需要排序
sb.Append("SELECT ");
if (index == 1) { sb.Append("TOP " + size + " "); }
sb.Append(select+" FROM ");
if (index > 1){sb.Append("(SELECT ROW_NUMBER() OVER(" + (!string.IsNullOrEmpty(orderby)?"ORDER BY "+orderby:string.Empty) + ") AS ROWID," + select + " FROM ");}
sb.Append(tbname);
sb.Append(!string.IsNullOrEmpty(where) ? " WHERE " + where : string.Empty);
if (index > 1)
{
sb.Append(") AS " + tbname + " WHERE ROWID BETWEEN " + ((index - 1) * size + 1) + " AND " + size * index);
}
else
{
sb.Append(!string.IsNullOrEmpty(orderby) ? " ORDER BY " + orderby : string.Empty);
}
return sb.ToString();
}
IDataParameter IHelper.Cp(string name, object value) { return new SqlParameter(name, value); }
string IHelper.ParStr(string name) { return "@"+name;}

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string IHelper.GetIdStr { get { return "SELECT @@IDENTITY"; } }
void IDisposable.Dispose()
{
CloseCon(); con.Dispose(); cmd.Dispose();
}
}

MsSql2005开始支持MARS，默认为关闭状态，也可以重写个支持MARS的Help,默认开启2个连接,一个用于查询一个用于无事物的执行,代码如下：

class MsMars:IHelper//自动开启mars,连接0为查询连接,连接1为执行无事务连接,事务连接为新连接
{
static SqlConnectionStringBuilder ssb;
static SqlConnection[] globalCon;
static object ck = new object();
public MsMars(string constr)
{
if (ssb == null)
{
ssb = new SqlConnectionStringBuilder(constr); ssb.MultipleActiveResultSets = true;
}
}
static SqlCommand GetCmd(int i = 3)
{
if (ssb == null) { throw new Exception("连接未初始化..."); }
if (i >=

3

) { return new SqlConnection(ssb.ConnectionString).CreateCommand(); }
if (globalCon != null) { return globalCon[i].CreateCommand(); }
lock (ck)
{
if (globalCon != null) { return globalCon[i].CreateCommand(); }
globalCon = new SqlConnection[2] { new SqlConnection(ssb.ConnectionString), new SqlConnection(ssb.ConnectionString) };
globalCon[0].Open(); globalCon[1].Open();
}
return globalCon[i].CreateCommand();
}
SqlCommand cmd;
void SetCmd(string txt, IEnumerable<IDataParameter> ps, bool issp)
{
cmd.Parameters.Clear();
cmd.CommandText = txt;
cmd.CommandType = issp ? CommandType.StoredProcedure : CommandType.Text;
cmd.Parameters.AddRange(ps.ToArray());
}
public int ExecuteQuery(string txt, IEnumerable<IDataParameter> ps, bool issp)
{
cmd = cmd ?? GetCmd(1);
SetCmd(txt, ps, issp);
return cmd.ExecuteNonQuery();
}
public object ExectueScalar(string txt, IEnumerable<IDataParameter> ps, bool issp)
{
cmd = cmd ?? GetCmd(1);
SetCmd(txt, ps, issp);
return cmd.ExecuteScalar();
}
public IDataReader ExectueReader(string txt, IEnumerable<IDataParameter> ps, bool issp)
{
cmd =cmd??GetCmd(0);
SetCmd(txt, ps, issp);
return cmd.ExecuteReader();
}
public void BegTran()
{
cmd = GetCmd();
cmd.Transaction = cmd.Connection.BeginTransaction();
}
public void RollBack()
{
cmd.Transaction.Rollback();
cmd.Connection.Close();cmd.Dispose();
}
public void Commit()
{
cmd.Transaction.Commit();
cmd.Connection.Close(); cmd.Dispose();
}
public string CreateSql(string select, string tbname, string where, string orderby, int size, int index)...
public IDataParameter Cp(string name, object value)...
public string GetIdStr...

public string ParStr(string name)...
public void Dispose()...