/// <summary>
/// 使用关键字id从数据库中查找，返回entityType类的实例
/// </summary>
/// <param name="connector"></param>
/// <param name="entityType"></param>
/// <param name="id"></param>
/// <returns></returns>
public static async Task <T> FindEntity <T>(DbConnector connector, int id) where T : new()
{
Type entityType = typeof(T);
object[] tableAttributes = entityType.GetCustomAttributes(typeof(DbTableAttribute), false);
if (tableAttributes == null || tableAttributes.Length != 1)
{
throw new Exception("使用FindEntity()方法，类" + entityType.FullName + "必须标记唯一的DbTable特性。");
}
DbTableAttribute tableAttr = (DbTableAttribute)tableAttributes[0];
string tableName = tableAttr.TableName;
string keyName = string.Empty;
foreach (PropertyInfo propertyInfo in entityType.GetProperties())
{
if (!propertyInfo.IsDefined(typeof(DbFieldAttribute), false))
{
continue;
}
DbFieldAttribute fldAttr = (DbFieldAttribute)(DbFieldAttribute.GetCustomAttribute(propertyInfo, typeof(DbFieldAttribute)));
if (fldAttr.IsPrimaryKey)
{
keyName = fldAttr.FieldName;
break;
}
}
string sql = string.Format(@"SELECT * FROM {0} WHERE {1}={2};", tableName, keyName, id);
DataTable table = await connector.ExecuteSqlQueryTable(sql);
if (table == null || table.Rows.Count == 0)
{
return(default(T));
}
else
{
object obj = Activator.CreateInstance(entityType);
ValueHelper.FulfillEntity(entityType, table.Rows[0], ref obj);
return((T)obj);
}
}