如何使用Dapper执行插入并返回插入的标识？

Question

如何对数据库执行插入并使用Dapper返回插入的标识？

我尝试过这样的事情:

string sql = "DECLARE @ID int; " +
             "INSERT INTO [MyTable] ([Stuff]) VALUES (@Stuff); " +
             "SELECT @ID = SCOPE_IDENTITY()";

var id = connection.Query<int>(sql, new { Stuff = mystuff}).First();

但它没有用.

@Marc Gravell谢谢你的回复.我已经尝试过你的解决方案但是,下面仍有相同的异常跟踪

System.InvalidCastException: Specified cast is not valid

at Dapper.SqlMapper.<QueryInternal>d__a`1.MoveNext() in (snip)\Dapper\SqlMapper.cs:line 610
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in (snip)\Dapper\SqlMapper.cs:line 538
at Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param) in (snip)\Dapper\SqlMapper.cs:line 456

Answer 1

如果使用它确实支持输入/输出参数(包括RETURN值)DynamicParameters,但在这种情况下,更简单的选项就是:

string sql = @"
INSERT INTO [MyTable] ([Stuff]) VALUES (@Stuff);
SELECT CAST(SCOPE_IDENTITY() as int)";

var id = connection.Query<int>(sql, new { Stuff = mystuff}).Single();

Answer 2

KB:2019779,"使用SCOPE_IDENTITY()和@@ IDENTITY时可能会收到不正确的值",OUTPUT子句是最安全的机制:

string sql = @"
DECLARE @InsertedRows AS TABLE (Id int);
INSERT INTO [MyTable] ([Stuff]) OUTPUT Inserted.Id INTO @InsertedRows
VALUES (@Stuff);
SELECT Id FROM @InsertedRows";

var id = connection.Query<int>(sql, new { Stuff = mystuff}).Single();

Answer 3

一个迟到的答案,但这里是我们最终使用的答案的替代方案SCOPE_IDENTITY():OUTPUT INSERTED

仅返回插入对象的ID:

它允许您获取插入行的全部或部分属性:

string insertUserSql = @"INSERT INTO dbo.[User](Username, Phone, Email)
                        OUTPUT INSERTED.[Id]
                        VALUES(@Username, @Phone, @Email);";

int newUserId = conn.QuerySingle<int>(insertUserSql,
                                new
                                {
                                    Username = "lorem ipsum",
                                    Phone = "555-123",
                                    Email = "lorem ipsum"
                                }, tran);

返回带ID的插入对象:

如果你想你能得到Phone和Email甚至整个插排:

string insertUserSql = @"INSERT INTO dbo.[User](Username, Phone, Email)
                        OUTPUT INSERTED.*
                        VALUES(@Username, @Phone, @Email);";

User newUser = conn.QuerySingle<User>(insertUserSql,
                                new
                                {
                                    Username = "lorem ipsum",
                                    Phone = "555-123",
                                    Email = "lorem ipsum"
                                }, tran);

此外,使用此功能,您可以返回已删除或更新的行的数据.如果您使用触发器,请小心,因为:

从OUTPUT返回的列反映了INSERT,UPDATE或DELETE语句完成之后但在执行触发器之前的数据.

对于INSTEAD OF触发器,生成的返回结果就像INSERT,UPDATE或DELETE实际发生一样,即使触发操作没有发生任何修改也是如此.如果在触发器主体内部使用包含OUTPUT子句的语句,则必须使用表别名来引用触发器插入和删除的表,以避免使用与OUTPUT关联的INSERTED和DELETED表重复列引用.

更多关于它的文档:链接

Answer 4

您获得的InvalidCastException是由于SCOPE_IDENTITY是十进制(38,0).

您可以通过如下方式将其作为int返回:

string sql = @"
INSERT INTO [MyTable] ([Stuff]) VALUES (@Stuff);
SELECT CAST(SCOPE_IDENTITY() AS INT)";

int id = connection.Query<int>(sql, new { Stuff = mystuff}).Single();