/// <summary>
/// 根据查询参数获取其中的某些值
/// </summary>
/// <param name="value_columns">获取值的列</param>
/// <param name="query_param">查询参数</param>
/// <returns></returns>
public static T getValues <T>(List <DBColumn> value_columns, DBQueryParamList query_param)
{
var table = tableInfo <T>();
if (query_param == null || query_param.count == 0)
{
return(default(T));
}
var query = new StringBuilder();
query.Append("select ");
foreach (DBColumn col in value_columns)
{
query.Append($"{DBUtil.connection.left_quote}{col.name}{DBUtil.connection.right_quote},");
}
if (query[query.Length - 1] == ',')
{
query.Remove(query.Length - 1, 1);
}
query.Append($" from {DBUtil.connection.left_quote}{table.table_name}{DBUtil.connection.right_quote} ");
var query_string = new StringBuilder();
var pm = new List <DBParameter>();
foreach (DBQueryParam param in query_param.pm_list)
{
//如果有参数传递为空值, 则代表本次查询不能查询到想要的结果(会把结果集扩大化), 此时返回为查询失败
if (!param.isAvailableWithValue())
{
return(default);
/// <summary>
/// 根据更新Model获取当前实例
/// --如果记录不存在, 返回带有更新Model内容的新实例
/// --如果记录存在, 返回原有实例并根据情况更新传入model中的内容
/// --如果返回为空值, 则表示传入的model与现有实例的某些值冲突, 无法赋值
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="update_model"></param>
/// <returns></returns>
public static T instanceByUpdate <T>(UpdateModelBase update_model)
{
var pm = DBQueryParamList.create();
var table = tableInfo <T>();
T instance = default(T);
try
{
foreach (var col in table.primary_columns)
{
pm.add(new DBQueryParam(col, update_model.getValue(col.name)));
}
instance = get <T>(pm);
}
catch { }
if (instance == null)
{
instance = Activator.CreateInstance <T>();
}
if (update_model != null)
{
update_model.setValuesTo(ref instance);
}
try
{
var method = typeof(T).GetMethod("processRefFeilds");
if (method != null)
{
method.Invoke(instance, null);
}
}
catch { }
return(instance);
}
/// <summary>
/// 使用当前参数创建一个查询参数列表
/// 注: 如果查询条件不可用, 创建列表中则不会包含本参数
/// </summary>
/// <returns></returns>
public DBQueryParamList createList()
{
DBQueryParamList list = new DBQueryParamList();
if (isAvailable())
{
list.add(this);
}
return(list);
}
/// <summary>
/// 通过查询参数获取实例
/// </summary>
/// <param name="query_param">查询参数</param>
/// <returns></returns>
public static T get <T>(DBQueryParamList query_param)
{
var table = tableInfo <T>();
if (query_param == null || query_param.count == 0)
{
return(default(T));
}
var query = new StringBuilder();
query.Append($"select * from {DBUtil.connection.left_quote}{table.table_name}{DBUtil.connection.right_quote}");
var query_string = new StringBuilder();
List <DBParameter> pm = new List <DBParameter>();
foreach (DBQueryParam param in query_param.pm_list)
{
//如果有参数传递为空值, 则代表本次查询不能查询到想要的结果(会把结果集扩大化), 此时返回为查询失败
if (!param.isAvailableWithValue())
{
return(default(T));
}
if (query_string.Length > 0)
{
query_string.Append(" and ");
}
query_string.Append(param.queryString());
param.setQueryParameter(ref pm);
}
if (query_string.Length > 0)
{
query.Append($" where {query_string.ToString()}");
}
DataTable data = DBQuery.query(query.ToString(), pm);
try
{
var result = Activator.CreateInstance <T>();
foreach (DBColumn column in table.columns)
{
result.setValue(column.field_info, data.Rows[0][column.name]);
}
try
{
FieldInfo info = result.GetType().GetField("is_new");
info.SetValue(result, false);
}
catch { }
return(result);
}
catch { }
return(default(T));
}