使用大规模插入我获得DBNull试图获取scope_identity（）

本文介绍了使用大规模插入我获得DBNull试图获取scope_identity（）的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ MSDN文档说明SCOPE_IDENTITY ：查看源代码，似乎每次调用 Scalar（）打开一个新连接： ///< summary> ///返回单个结果 ///< / summary> public virtual object Scalar（string sql，params object [] args）{ object result = null; using（var conn = OpenConnection ））{// result = CreateCommand（sql，conn，args）.ExecuteScalar（）; } return result; } ... ///< summary> ///返回和OpenConnection ///< / summary> public virtual DbConnection OpenConnection（）{ var result = _factory.CreateConnection（）; result.ConnectionString = ConnectionString; result.Open（）; //< - ... and this return result; } 因此，每次你做 table.Scalar （select scope_identity（））; 你实际上是在一个新的连接（这意味着一个不同的会话/范围）。 这解释了 DBNull 结果。 但是因为你已经做了： var newID = table.Insert（...） 你可能需要在插入后检查 newID 的值; 至少，这是 Insert（）的代码让我相信： public virtual dynamic Insert（object o）{ var ex = o.ToExpando ; if（！IsValid（ex））{ throw new InvalidOperationException（Can not insert：+ String.Join（;，Errors.ToArray（）））; } if（BeforeSave（ex））{ using（dynamic conn = OpenConnection（））{ var cmd = CreateInsertCommand（ex）; cmd.Connection = conn; cmd.ExecuteNonQuery（）; cmd.CommandText =SELECT @@ IDENTITY as newID; ex.ID = cmd.ExecuteScalar（）; 插入（ex）; } return ex; } else { return null; } } I have a table with an identity column.Using Massive with code like this var table = new Categories();var newID = table.Insert(new {CategoryName = "Buck Fify Stuff", Description = "Things I like"});then table.Scalar("select scope_identity()");returns DBNull :(What do I need to do different to get the actual inserted identity value 解决方案 The MSDN documentation states that SCOPE_IDENTITY:Looking at the Massive source code, it appears that every call to Scalar() opens a new connection:/// <summary>/// Returns a single result/// </summary>public virtual object Scalar(string sql, params object[] args) { object result = null; using (var conn = OpenConnection()) { // <-- see this ... result = CreateCommand(sql, conn, args).ExecuteScalar(); } return result;}.../// <summary>/// Returns and OpenConnection/// </summary>public virtual DbConnection OpenConnection() { var result = _factory.CreateConnection(); result.ConnectionString = ConnectionString; result.Open(); // <-- ...and this return result;}Therefore, every time you are doing table.Scalar("select scope_identity()"); you are actually doing this in a new connection (which means a different session/scope).This explains the DBNull result.But since you are already doing:var newID = table.Insert(...)you might want to inspect the value of newID after the insert happens; I hope you'll find something nice in there.At least, that's what the code for Insert() leads me to believe: public virtual dynamic Insert(object o) { var ex = o.ToExpando(); if (!IsValid(ex)) { throw new InvalidOperationException("Can't insert: " + String.Join("; ", Errors.ToArray())); } if (BeforeSave(ex)) { using (dynamic conn = OpenConnection()) { var cmd = CreateInsertCommand(ex); cmd.Connection = conn; cmd.ExecuteNonQuery(); cmd.CommandText = "SELECT @@IDENTITY as newID"; ex.ID = cmd.ExecuteScalar(); Inserted(ex); } return ex; } else { return null; } } 这篇关于使用大规模插入我获得DBNull试图获取scope_identity（）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！