/// <summary>
/// 根据主键获取实体
/// </summary>
/// <typeparam name="T">实体类型</typeparam>
/// <param name="idb">数据库连接上下文</param>
/// <param name="pk">主键 例如id=1 写入 GetEntityById(1)</param>
/// <returns>如果存在该实体，返回实体，否则返回null。</returns>
/// <remarks>
/// 对于多主键实体，主键的顺序必须是 实体的顺序否则系统会取不到正确的数据。
///
/// </remarks>
public static T GetEntityById <T>(this IDbHelper idb, params object[] pk) where T : class, new()
{
// 根据实体获取主键
var pklist = DALUtil.GetPKAttribute <T>();
if (pklist.Count != pk.Count())
{
// 实体的主键 个数如果不一致 系统自动抛出异常
throw new Exception("主键设置个数不一致");
}
List <IDataParameter> list = new List <IDataParameter>();
string where = "1=1";
for (int i = 0; i < pklist.Count; i++)
{
where += " AND " + pklist[i] + " = " + DALUtil.GetParameterPrefix(idb) + i.ToString();
var idp = idb.GetIDataParameter();
idp.ParameterName = DALUtil.GetParameterPrefix(idb) + i.ToString();
idp.Value = pk[i];
list.Add(idp);
}
var dt = idb.ExecuteTable(CommandType.Text, string.Format("SELECT * FROM {0} WHERE {1}", DALUtil.GetTableName <T>(), where), list.ToArray());
if (dt.Rows.Count > 0)
{
return(DALUtil.GetEntity <T>(dt)[0]);
}
else
{
return(default(T));
}
}
/// <summary>
/// 根据指定主键删除一个实体
/// </summary>
/// <typeparam name="T">实体泛型</typeparam>
/// <param name="idb">数据库连接上下文</param>
/// <param name="pk">主键列表，注意：主键列表的顺序必须与实体完全一致</param>
/// <returns>返回影响的记录条数，如果该数据不存在返回0</returns>
public static int Delete <T>(this IDbHelper idb, object[] pk) where T : class, new()
{
string tablename = DALUtil.GetTableName <T>();
var pks = DALUtil.GetPKAttribute <T>();
if (pks.Count != pk.Length)
{
throw new Exception("主键个数与传入参数不一致");
}
StringBuilder sb = new StringBuilder();
for (int i = 0; i < pk.Length; i++)
{
sb.AppendFormat(" AND {0} = '{1}'", pks[i], pk[i]);
}
string sql = string.Format("DELETE FROM {0} WHERE 1=1{1}", tablename, sb.ToString());
return(idb.ExecuteNonQuery(sql));
}