Using Massive Insert I get DBNull when trying to get scope_identity() - sql

Question

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

Answer 1

The MSDN documentation states that SCOPE_IDENTITY:
"retrieves the last identity values that are generated in any table in the current session"
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;
}
}