使用LINQ将嵌套对象保存到实体

你需要注意两个步骤。(1)添加新选择的值,(2)删除未选择的值。在可查找类中,您需要这样的方法。

public void SynchronizeDataTables(IEnumerable<DataTable> dataTables)
{
    // get the current data tables. call ToList() to force and enumeration.
    // without the ToList(), you'll get a "Sequence Changed during Enumeration"
    // error
    var currentDataTables = MapTable.Select(m => m.DataTable).ToList();

    // if the table is selected, but not in the data store add it.
    foreach (var dataTable in dataTables)
    {
        if (!currentDataTables.Contains(dataTable))
        {
            MapTables.Add(new MapTable { DataTable = dataTable });
        }
    }

    // if the table is in the data store, but not selected, then remove it.
    foreach (var dataTable in currentDataTables)
    {
        if (!dataTables.Contains(dataTable))
        {
            MapTables.Remove(dataTable);
        }
    }
}

编辑 :执行此操作时,我使用的是Linq to SQL,我只循环使用选定的ID,而不是整个对象。这更复杂,因为LinqToEntities创建的对象与LinqToSQL稍有不同,因为它不公开FK标识。轻微修改如下:

public void SynchronizeDataTables(IEnumerable<int> dataTableIds)
{
    // get the current data tables. call ToList() to force and enumeration.
    // without the ToList(), you'll get a "Sequence Changed during Enumeration"
    // error
    var currentDataTableIds = MapTable.Select(m => m.DataTable.Id).ToList();

    // if the table is selected, but not in the data store add it.
    foreach (var dataTableId in dataTableIds)
    {
        if (!currentDataTableIds.Contains(dataTableId))
        {
            var dataTable = ???; // some method to fetch data table with ID = dataTableId
            MapTables.Add(new MapTable { DataTable = dataTable });
        }
    }

    // if the table is in the data store, but not selected, then remove it.
    foreach (var dataTable in currentDataTableIds )
    {
        if (!dataTableIds.Contains(dataTableId ))
        {
            var dataTable = ???; // some method to fetch data table with ID = dataTableId
            MapTables.Remove(dataTable);
        }
    }
}