Question

我有如下多对多的关系：

Table1
ID (int) | Name (string)

Table2
ID (int) | Data (string)

Table1_2
Table1ID (int) | Table2ID (int)

我想在Entity Framework中执行以下操作：

给定List<Table1>，查看Table1中是否有匹配的记录;如果是的话，引用它们;如果没有，添加它们并引用它们。例如，像：

public void InsertOrReferenceExisting(string data, List<Table1> table1References)
{
    var myEntities = new MyEntities();
    var table1Entities = new EntityCollection<Table1>();
    foreach(var row in table1References)
    {
            var existing = myEntities.Table1.Where(x => x.Name == row.Name);
            if (existing.Count() > 0)
            {
                // reference existing row in Table1
            }
            else
            {
                // add new row to Table1
            }
    }
    myEntities.Table2.AddObject(new Table2
        {
            Data = data,
            Table1s = table1Entities
        });
    myEntities.SaveChanges(SaveOptions.AcceptAllChangesAfterSave);
}

我是在正确的轨道上吗？

Answer 1

尝试一下：

public void InsertOrReferenceExisting(string data, List<Table1> table1References)
{
    using (var myEntities = new MyEntities())
    {
        var tbl2 = myEntities.Table2.CreateObject();
        tbl2.Data = data;
        myEntities.Table2.AddObject(tbl2);
        foreach (var row in table1References)
        {
            var tbl1 = myEntities.Table1.Where(x => x.Name == row.Name).FirstOrDefault();
            if (tbl1 == null)
            {
                tbl1 = myEntities.Table1.CreateObject();
                tbl1.Name = row.Name;
            }

            tbl2.Table1.Add(tbl1);
        }

        myEntities.SaveChanges();
    }
}

请注意，此解决方案不允许Table1中的多个记录在“名称”列中具有相同的值。您可能应该在数据库级别使用唯一约束来强制执行该操作。

引用现有记录或为EF中的多对多关系添加新记录

1 个答案: