Dapper + MSAccess:如何获取插入行的标识符 [英] Dapper + MSAccess: How to get identifier of inserted row

问题描述

我正在使用带有C#的Dapper，后端是MS Access.我的DAL方法在数据库中插入记录.我想返回插入行的唯一标识符(或使用唯一标识符更新的POCO). 我期望我的功能如下(我知道这不起作用；只是为了解释我想要的):-

I am using Dapper with C# and back end is MS Access. My DAL method inserts record in database. I want to return unique identifier (or updated POCO with unique identifier) of the inserted row. I am expecting my function something like follows (I know this does not work; just to explain what I want): -

public MyPoco Insert(MyPoco myPoco)
{
    sql = @"INSERT INTO MyTable (Field1, Field2) VALUES (@Field1, @Field2)";
    var param = GetMappedParams(myPoco);//ID property here is null.
    var result = _connection.Query<MyPoco>(sql, param, null, false, null, CommandType.Text);.Single();
    return result;//This result now contains ID that is created by database.
}

我来自NHibernate世界，POCO随NH一起自动更新.如果不;我们可以调用Refresh方法并更新ID. 我不知道如何使用Dapper实现这一目标.

I am from NHibernate world and POCO updates automatically with NH. If not; we can call Refresh method and it updates the ID. I am not aware how to achieve this with Dapper.

我阅读了这篇文章关于SO的问题，它与SQL Server无关.

I read this question on SO which is not relevant as it talks about SQL Server.

另一个此问题尚未接受答案.

Another this question does not have accepted answer.

我阅读了这个问题，在哪里接受了答案解释了使用@@Identity的陷阱.

I read this question where accepted answer explains pit-falls of using @@Identity.

推荐答案

这对我有用:

static MyPoco Insert(MyPoco myPoco)
{
    string sql = "INSERT INTO MyTable (Field1, Field2) VALUES (@Field1, @Field2)";
    _connection.Execute(sql, new {myPoco.Field1, myPoco.Field2});
    myPoco.ID = _connection.Query<int>("SELECT @@IDENTITY").Single();
    return myPoco;  // This result now contains ID that is created by database.
}

请注意，这将与Access数据库的OleDbConnection一起使用，但与OdbcConnection一起使用不.

Note that this will work with an OleDbConnection to the Access database, but it will not work with an OdbcConnection.

编辑以下内容:评论

要确保INSERT和SELECT调用之间的连接保持打开状态，我们可以这样做:

To ensure that the Connection remains open between the INSERT and the SELECT calls, we could do this:

static void Insert(MyPoco myPoco)
{
    string sql = "INSERT INTO MyTable (Field1, Field2) VALUES (@Field1, @Field2)";
    bool connAlreadyOpen = (_connection.State == System.Data.ConnectionState.Open);
    if (!connAlreadyOpen)
    {
        _connection.Open();
    }
    _connection.Execute(sql, new {myPoco.Field1, myPoco.Field2});
    myPoco.ID = _connection.Query<int>("SELECT @@IDENTITY").Single();
    if (!connAlreadyOpen)
    {
        _connection.Close();
    }
    return;  // (myPoco now contains ID that is created by database.)
}

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